An immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. A disease is an abnormal condition of an organism that impairs bodily functions and can be deadly A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable See also Parasitic worm (disambiguation Parasitic worms or helminths are a division of eukaroytic Parasites that unlike external parasites such The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Tissue is a cellular organizational level intermediate between cells and a complete organism Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism. eVolution is the third Album by eLDee, it was due to be released in 2008 In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment
To survive this challenge, multiple mechanisms evolved that recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess enzyme systems that protect against viral infections. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins This article is about a biological infectious particle for other uses see Phage (disambiguation. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants, fish, reptiles, and insects. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Plants are living Organisms belonging to the kingdom Plantae. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described These mechanisms include antimicrobial peptides called defensins, phagocytosis, and the complement system. Antimicrobial peptides (also called host defence peptides are an evolutionarily conserved component of the innate immune response and are found among all classes of life Defensins are small (15-20 residue) Cysteine -rich Cationic Proteins found in both Vertebrates and Invertebrates They are Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole The complement system is a Biochemical cascade that helps clear Pathogens from an organism More sophisticated mechanisms, however, developed relatively recently, with the evolution of vertebrates. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes [1] The immune systems of vertebrates such as humans consist of many types of proteins, cells, organs, and tissues, which interact in an elaborate and dynamic network. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument As part of this more complex immune response, the vertebrate system adapts over time to recognize particular pathogens more efficiently. The adaptation process creates immunological memories and allows even more effective protection during future encounters with these pathogens. Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion This process of acquired immunity is the basis of vaccination. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic Vaccination is the administration of Antigenic material (the Vaccine) to produce immunity to a disease
Disorders in the immune system can result in disease. Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised Immunodeficiency can either be the result of a genetic disease, such as severe combined immunodeficiency, or be produced by pharmaceuticals or an infection, such as the acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired Severe combined immunodeficiency ( SCID) or Boy in the Bubble Syndrome is a genetic disorder in which both "arms" ( B cells and T cells A retrovirus is any Virus belonging to the viral family Retroviridae. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome In contrast, autoimmune diseases result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues Common autoimmune diseases include rheumatoid arthritis, diabetes mellitus type 1 and lupus erythematosus. Rheumatoid arthritis ( RA) is a chronic systemic autoimmune disorder that causes the Immune system to attack the Joints, where Diabetes mellitus type 1 (Type 1 diabetes Type I diabetes T1D T1DM IDDM juvenile diabetes is a form of Diabetes mellitus. Systemic lupus erythematosus ( SLE or lupus,) is a chronic autoimmune disease that can be fatal though with recent medical advances fatalities are becoming These critical roles of immunology in health and disease are areas of intense scientific study. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with
Layered defense in immunity
The immune system protects organisms from infection with layered defenses of increasing specificity. An infection is the detrimental Colonization of a host Organism by a foreign Species. Most simply, physical barriers prevent pathogens such as bacteria and viruses from entering the organism. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response. Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner Innate immune systems are found in all plants and animals. Plants are living Organisms belonging to the kingdom Plantae. [2] However, if pathogens successfully evade the innate response, vertebrates possess a third layer of protection, the adaptive immune system, which is activated by the innate response. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic Here, the immune system adapts its response during an infection to improve its recognition of the pathogen. This improved response is then retained after the pathogen has been eliminated, in the form of an immunological memory, and allows the adaptive immune system to mount faster and stronger attacks each time this pathogen is encountered. Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion [3]
| Innate immune system | Adaptive immune system |
|---|---|
| Response is non-specific | Pathogen and antigen specific response |
| Exposure leads to immediate maximal response | Lag time between exposure and maximal response |
| Cell-mediated and humoral components | Cell-mediated and humoral components |
| No immunological memory | Exposure leads to immunological memory |
| Found in nearly all forms of life | Found only in jawed vertebrates |
Both innate and adaptive immunity depend on the ability of the immune system to distinguish between self and non-self molecules. An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response Cell-mediated immunity is an Immune response that does not involve Antibodies or complement but rather involves the activation of Macrophages The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves Cell-mediated immunity is an Immune response that does not involve Antibodies or complement but rather involves the activation of Macrophages The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion Gnathostomata is the group of Vertebrates with Jaws The group is traditionally a superclass, including the familiar classes of Fish, In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by In immunology, self molecules are those components of an organism's body that can be distinguished from foreign substances by the immune system. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with [4] Conversely, non-self molecules are those recognized as foreign molecules. One class of non-self molecules are called antigens (short for antibody generators) and are defined as substances that bind to specific immune receptors and elicit an immune response. An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response An immune receptor (or immunologic receptor) is a receptor, usually on a Cell membrane, which binds to a substance (for example a Cytokine) [5]
Surface barriers
Several barriers protect organisms from infection, including mechanical, chemical and biological barriers. The waxy cuticle of many leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs, and skin are examples of the mechanical barriers that are the first line of defense against infection. Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs without Periderm In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described The term eggshell is a term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. The skin is the outer covering of living tissue of an animal (or plant [5] However, as organisms cannot be completely sealed against their environments, other systems act to protect body openings such as the lungs, intestines, and the genitourinary tract. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists In Anatomy, the genitourinary system is the Organ system of all the Reproductive organs and the Urinary system. In the lungs, coughing and sneezing mechanically eject pathogens and other irritants from the respiratory tract. In Medicine, a cough ( Latin: tussis) is a sudden and often repetitively occurring defence Reflex which helps to clear the large breathing passages A sneeze (or sternutation) is a semi-autonomous Convulsive expulsion of Air from the Lungs, most commonly caused by foreign particles Irritation or exacerbation, in Biology and Physiology, is a state of Inflammation or painful reaction to Allergy or cell-lining damage In humans the respiratory tract is the part of the Anatomy that has to do with the process of respiration. The flushing action of tears and urine also mechanically expels pathogens, while mucus secreted by the respiratory and gastrointestinal tract serves to trap and entangle microorganisms. Tears are the liquid product of a process of lacrimation to clean and lubricate the Eyes The word lacrimation may also be used in a medical or literary sense Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra. In vertebrates mucus is a slippery secretion produced by and covering Mucous membranes It is a viscous Colloid containing Antiseptic enzymes (such as A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually [6]
Chemical barriers also protect against infection. The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins. Antimicrobial peptides (also called host defence peptides are an evolutionarily conserved component of the innate immune response and are found among all classes of life Defensins are small (15-20 residue) Cysteine -rich Cationic Proteins found in both Vertebrates and Invertebrates They are [7] Enzymes such as lysozyme and phospholipase A2 in saliva, tears, and breast milk are also antibacterials. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Lysozyme is a family of Enzymes ( which damage bacterial cell walls by catalyzing Hydrolysis of 14-beta-linkages between N-acetylmuramic acid and Phospholipases A2 (PLA2s are upstream regulators of many inflammatory processes For the band see Saliva (band; for the village in Azerbaijan see Səliva. Breast milk refers to the Milk produced by a mother to feed her baby Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive" are antimicrobial [8][9] Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while semen contains defensins and zinc to kill pathogens. The vagina (from Latin, literally " Sheath " or " Scabbard " is a fibromuscular tubular tract leading from the Uterus Menarche (American English məˈnɑrki British English mɛˈnɑːki is the first menstrual period, or first menstrual bleeding in the females of Human beings In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Physiological aspects Internal and external fertilization Depending on the Species, spermatozoa can fertilize Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 [10][11] In the stomach, gastric acid and proteases serve as powerful chemical defenses against ingested pathogens. In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following Gastric acid is one of the main Secretions of the Stomach, together with several Enzymes and Intrinsic factor. A protease is any Enzyme that conducts Proteolysis, that is begins protein Catabolism by Hydrolysis of the Peptide bonds that link
Within the genitourinary and gastrointestinal tracts, commensal flora serve as biological barriers by competing with pathogenic bacteria for food and space and, in some cases, by changing the conditions in their environment, such as pH or available iron. In Ecology, commensalism is a kind of symbiotic relationship between two organisms where one benefits and the other is not significantly harmed or helped (like a bird The gut flora are the Microorganisms that normally live in the Digestive tract and can perform a number of useful functions for their hosts pH is the measure of the acidity or alkalinity of a Solution. [12] This reduces the probability that pathogens will be able to reach sufficient numbers to cause illness. However, since most antibiotics non-specifically target bacteria and do not affect fungi, oral antibiotics can lead to an “overgrowth” of fungi and cause conditions such as a vaginal candidiasis (yeast infection). In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Candidiasis, commonly called yeast infection or thrush, is a Fungal infection (mycosis of any of the Candida species of which [13] There is good evidence that re-introduction of probiotic flora, such as pure cultures of the lactobacilli normally found in yoghurt, helps restore a healthy balance of microbial populations in intestinal infections in children and encouraging preliminary data in studies on bacterial gastroenteritis, inflammatory bowel diseases, urinary tract infection and post-surgical infections. Probiotics are Dietary supplements containing potentially beneficial Bacteria or Yeasts According to the currently adopted definition by FAO / Lactobacillus is a Genus of Gram-positive Facultative anaerobic or Microaerophilic Bacteria. Yoghurt, yogurt, yoghourt, youghurt or yogourt (see spelling below is a Gastroenteritis (also known as gastro, gastric flu, and stomach flu, although unrelated to Influenza) is Inflammation of the In Medicine, inflammatory bowel disease ( IBD) is a group of inflammatory conditions of the large intestine and Small intestine A urinary tract infection ( UTI) is a bacterial Infection that affects any part of the Urinary tract. Perioperative mortality is mortality in relation to Surgery, usually taken as death within two weeks of a surgical procedure [14][15][16]
Innate immunity
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For more details on this topic, see Innate immune system. Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner
Microorganisms that successfully enter an organism will encounter the cells and mechanisms of the innate immune system. The innate response is usually triggered when microbes are identified by pattern recognition receptors, which recognize components that are conserved among broad groups of microorganisms. Pattern recognition receptors, or PRR s are Proteins expressed by cells of the Immune system to identify molecules associated with microbial Pathogens [17] Innate immune defenses are non-specific, meaning these systems respond to pathogens in a generic way. [5] This system does not confer long-lasting immunity against a pathogen. Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion The innate immune system is the dominant system of host defense in most organisms. [2]
Humoral and chemical barriers
Inflammation
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For more details on this topic, see Inflammation. Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens
Inflammation is one of the first responses of the immune system to infection. [18] The symptoms of inflammation are redness and swelling, which are caused by increased blood flow into a tissue. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Inflammation is produced by eicosanoids and cytokines, which are released by injured or infected cells. In biochemistry eicosanoids are signaling molecules made by Oxygenation of twenty-carbon Essential fatty acids (EFAs Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular Eicosanoids include prostaglandins that produce fever and the dilation of blood vessels associated with inflammation, and leukotrienes that attract certain white blood cells (leukocytes). A prostaglandin is any member of a group of Lipid compounds that are derived enzymatically from Fatty acids and have important functions in the Animal body Fever (also known as pyrexia, from the Greek pyretos meaning fire or a febrile response, from the Latin word Febris Leukotrienes are naturally produced Eicosanoid lipid mediators, which may be responsible for the effects of an inflammatory response [19][20] Common cytokines include interleukins that are responsible for communication between white blood cells; chemokines that promote chemotaxis; and interferons that have anti-viral effects, such as shutting down protein synthesis in the host cell. Interleukins are a group of Cytokines (secreted Signaling molecules) that were first seen to be expressed by White blood cells ( Leukocytes hence Chemokines are a family of small Cytokines, or Proteins secreted by cells Proteins are classified as chemokines according to shared structural characteristics Chemotaxis, a kind of Taxis, is the phenomenon in which bodily cells bacteria, and other single-cell or Multicellular organisms direct their movements Interferons ( IFN s are natural Proteins produced by the cells of the Immune system of most Vertebrates in response to challenges by foreign agents Protein biosynthesis (synthesis is the process in which cells build Proteins The term is sometimes used to refer only to protein translation but more [21] Growth factors and cytotoxic factors may also be released. The term growth factor refers to a naturally occurring Protein capable of stimulating cellular growth proliferation and Cellular differentiation. These cytokines and other chemicals recruit immune cells to the site of infection and promote healing of any damaged tissue following the removal of pathogens. [22]
Complement system
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For more details on this topic, see Complement system. The complement system is a Biochemical cascade that helps clear Pathogens from an organism
The complement system is a biochemical cascade that attacks the surfaces of foreign cells. A biochemical cascade is a series of Chemical reactions in which the products of one reaction are consumed in the next reaction It contains over 20 different proteins and is named for its ability to “complement” the killing of pathogens by antibodies. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Complement is the major humoral component of the innate immune response. The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves [23][24] Many species have complement systems, including non-mammals like plants, fish, and some invertebrates. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate [25]
In humans, this response is activated by complement binding to antibodies that have attached to these microbes or the binding of complement proteins to carbohydrates on the surfaces of microbes. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually This recognition signal triggers a rapid killing response. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions [26] The speed of the response is a result of signal amplification that occurs following sequential proteolytic activation of complement molecules, which are also proteases. Proteolysis is the directed degradation ( digestion) of Proteins by cellular Enzymes called Proteases or by intramolecular digestion A protease is any Enzyme that conducts Proteolysis, that is begins protein Catabolism by Hydrolysis of the Peptide bonds that link After complement proteins initially bind to the microbe, they activate their protease activity, which in turn activates other complement proteases, and so on. This produces a catalytic cascade that amplifies the initial signal by controlled positive feedback. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Positive feedback, sometimes referred to as "cumulative causation" is a Feedback loop system in which the system responds to perturbation in the same direction [27] The cascade results in the production of peptides that attract immune cells, increase vascular permeability, and opsonize (coat) the surface of a pathogen, marking it for destruction. Vascular permeability characterizes the capacity of a blood vessel wall to pass through small molecules (ions water nutrients or even whole cells ( Lymphocytes on their An opsonin is any molecule that acts as a binding Enhancer for the process of Phagocytosis, for example by coating the negatively-charged molecules on the membrane This deposition of complement can also kill cells directly by disrupting their plasma membrane. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer [23]
Cellular barriers of the innate system
Leukocytes (white blood cells) act like independent, single-celled organisms and are the second arm of the innate immune system. [5] The innate leukocytes include the phagocytes (macrophages, neutrophils, and dendritic cells), mast cells, eosinophils, basophils, and natural killer cells. Phagocytes are cells that are found in the blood bone marrow and other tissues of Vertebrates. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of White blood cells in humans and form an essential part of the Dendritic cells (DCs are Immune cells and form part of the Mammalian Immune system. A mast cell (or mastocyte) is a resident cell of several types of tissues and contains many granules rich in Histamine and Heparin Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components Natural killer cells (or NK cells) are a type of Cytotoxic Lymphocyte that constitute a major component of the Innate immune system. These cells identify and eliminate pathogens, either by attacking larger pathogens through contact or by engulfing and then killing microorganisms. [25] Innate cells are also important mediators in the activation of the adaptive immune system. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic [3]
Phagocytosis is an important feature of cellular innate immunity performed by cells called 'phagocytes' that engulf, or eat, pathogens or particles. Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole Phagocytes are cells that are found in the blood bone marrow and other tissues of Vertebrates. Phagocytes generally patrol the body searching for pathogens, but can be called to specific locations by cytokines. Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular [5] Once a pathogen has been engulfed by a phagocyte, it becomes trapped in an intracellular vesicle called a phagosome, which subsequently fuses with another vesicle called a lysosome to form a phagolysosome. A vesicle is a small bubble of liquid within a cell A more formal definition in Cell biology, would be that a vesicle is a relatively small intracellular membrane-enclosed In cell biology a phagosome is a Vacuole formed around a particle absorbed by Phagocytosis. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. A phagolysosome is a membrane-enclosed Organelle which is formed from the fusing of a Lysosome and a Phagosome. The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Respiratory burst (is sometimes called oxidative burst) is the rapid release of Reactive oxygen species (superoxide radical and hydrogen peroxide from different types In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell [28][29] Phagocytosis evolved as a means of acquiring nutrients, but this role was extended in phagocytes to include engulfment of pathogens as a defense mechanism. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment [30] Phagocytosis probably represents the oldest form of host defense, as phagocytes have been identified in both vertebrate and invertebrate animals. [31]
Neutrophils and macrophages are phagocytes that travel throughout the body in pursuit of invading pathogens. [32] Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, normally representing 50% to 60% of the total circulating leukocytes. This is an article about the rock music band "Circulatory System" [33] During the acute phase of inflammation, particularly as a result of bacterial infection, neutrophils migrate toward the site of inflammation in a process called chemotaxis, and are usually the first cells to arrive at the scene of infection. Macrophages are versatile cells that reside within tissues and produce a wide array of chemicals including enzymes, complement proteins, and regulatory factors such as interleukin 1. The complement system is a Biochemical cascade that helps clear Pathogens from an organism Interleukin-1 (IL-1 is one of the first Cytokines ever described [34] Macrophages also act as scavengers, ridding the body of worn-out cells and other debris, and as antigen-presenting cells that activate the adaptive immune system. See also Antigen presentation An antigen-presenting cell ( APC) or accessory cell is a cell that displays foreign Antigen complexed [3]
Dendritic cells (DC) are phagocytes in tissues that are in contact with the external environment; therefore, they are located mainly in the skin, nose, lungs, stomach, and intestines. The skin is the outer covering of living tissue of an animal (or plant Anatomically a nose is a protuberance in Vertebrates that houses the Nostrils or nares which admit and expel air for respiration in conjunction with the lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists [35] They are named for their resemblance to neuronal dendrites, as both have many spine-like projections, but dendritic cells are in no way connected to the nervous system. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information Dendrites (from Greek δένδρον déndron, “tree” are the branched projections of a Neuron that act to conduct the electrochemical The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself Dendritic cells serve as a link between the innate and adaptive immune systems, as they present antigen to T cells, one of the key cell types of the adaptive immune system. Antigen presentation is a process in the body's Immune system by which Macrophages, Dendritic cells and other cell types capture Antigens and T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. [35]
Mast cells reside in connective tissues and mucous membranes, and regulate the inflammatory response. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin covered in Epithelium, which are involved in [36] They are most often associated with allergy and anaphylaxis. Allergy is a disorder of the Immune system often also referred to as Atopy. Anaphylaxis is an acute systemic (multi-system and severe Type I Hypersensitivity allergic reaction in humans and other Mammals [33] Basophils and eosinophils are related to neutrophils. They secrete chemical mediators that are involved in defending against parasites and play a role in allergic reactions, such as asthma. Parasitism is a type of symbiotic relationship between Organisms of different Species. Asthma is a chronic Condition involving the Respiratory system in which the airways occasionally constrict become inflamed, and are [37] Natural killer (NK cells) cells are leukocytes that attack and destroy tumor cells, or cells that have been infected by viruses. Natural killer cells (or NK cells) are a type of Cytotoxic Lymphocyte that constitute a major component of the Innate immune system. See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic [38]
Adaptive immunity
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For more details on this topic, see Adaptive immune system. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic
The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is "remembered" by a signature antigen. [39] The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen presentation is a process in the body's Immune system by which Macrophages, Dendritic cells and other cell types capture Antigens and Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by "memory cells". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it.
Lymphocytes
The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. Hematopoietic stem cells (HSCs are Stem cells that give rise to all the blood cell types including Myeloid ( Monocytes and Macrophages, Neutrophils Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of [25] B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response. The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves Cell-mediated immunity is an Immune response that does not involve Antibodies or complement but rather involves the activation of Macrophages
Both B cells and T cells carry receptor molecules that recognize specific targets. T cells recognize a “non-self” target, such as a pathogen, only after antigens (small fragments of the pathogen) have been processed and presented in combination with a “self” receptor called a major histocompatibility complex (MHC) molecule. The major histocompatibility complex ( MHC) is a large genomic region or Gene family found in most Vertebrates It is the most gene-dense region There are two major subtypes of T cells: the killer T cell and the helper T cell. A cytotoxic T cell (also known as TC, CTL T-Killer cell cytolytic T cell CD8+ T-cells or killer T cell) belongs to a sub-group of T lymphocytes T helper cells (also known as effector T cells or Th cells) are a sub-group of Lymphocytes (a type of White blood cell or Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells only recognize antigens coupled to Class II MHC molecules. The major histocompatibility complex ( MHC) is a large genomic region or Gene family found in most Vertebrates It is the most gene-dense region The major histocompatibility complex ( MHC) is a large genomic region or Gene family found in most Vertebrates It is the most gene-dense region These two mechanisms of antigen presentation reflect the different roles of the two types of T cell. A third, minor subtype are the γδ T cells that recognize intact antigens that are not bound to MHC receptors. [40]
In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface, and recognizes whole pathogens without any need for antigen processing. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Antigen processing is a Biological process that prepares Antigens for presentation to special cells of the Immune system called T lymphocytes Each lineage of B cell expresses a different antibody, so the complete set of B cell antigen receptors represent all the antibodies that the body can manufacture. [25]
Killer T cells
Killer T cell are a sub-group of T cells that kill cells infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional. A cytotoxic T cell (also known as TC, CTL T-Killer cell cytolytic T cell CD8+ T-cells or killer T cell) belongs to a sub-group of T lymphocytes [42] As with B cells, each type of T cell recognises a different antigen. Killer T cells are activated when their T cell receptor (TCR) binds to this specific antigen in a complex with the MHC Class I receptor of another cell. The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells that is in general responsible for recognizing Antigens bound Recognition of this MHC:antigen complex is aided by a co-receptor on the T cell, called CD8. A co-receptor is a cell surface receptor that binds a signalling molecule in addition to a primary receptor in order to facilitate Ligand recognition and initiate CD8 ( Cluster of differentiation 8 is a transmembrane Glycoprotein that serves as a Co-receptor for the T cell receptor (TCR The T cell then travels throughout the body in search of cells where the MHC I receptors bear this antigen. When an activated T cell contacts such cells, it releases cytotoxins, such as perforin, which form pores in the target cell's plasma membrane, allowing ions, water and toxins to enter. Cytotoxicity is the quality of being toxic to cells Examples of toxic agents are a Chemical substance, an Immune cell or some types of Venom Perforin 1 (pore forming protein, also known as PRF1, is a human Gene. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge The entry of another toxin called granulysin (a protease) induces the target cell to undergo apoptosis. Granulysin is a substance released by Cytotoxic T cells ( CD8) when they are attached to infected body cells [43] T cell killing of host cells is particularly important in preventing the replication of viruses. T cell activation is tightly controlled and generally requires a very strong MHC/antigen activation signal, or additional activation signals provided by "helper" T cells (see below). [43]
Helper T cells
Helper T cells regulate both the innate and adaptive immune responses and help determine which types of immune responses the body will make to a particular pathogen. T helper cells (also known as effector T cells or Th cells) are a sub-group of Lymphocytes (a type of White blood cell or [44][45] These cells have no cytotoxic activity and do not kill infected cells or clear pathogens directly. They instead control the immune response by directing other cells to perform these tasks.
Helper T cells express T cell receptors (TCR) that recognize antigen bound to Class II MHC molecules. The MHC:antigen complex is also recognized by the helper cell's CD4 co-receptor, which recruits molecules inside the T cell (e. CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, g. Lck) that are responsible for T cell's activation. Lck (or leukocyte-specific protein tyrosine kinase) is a Protein that is found inside specialized cells of the Immune system called Helper T cells have a weaker association with the MHC:antigen complex than observed for killer T cells, meaning many receptors (around 200–300) on the helper T cell must be bound by an MHC:antigen in order to activate the helper cell, while killer T cells can be activated by engagement of a single MHC:antigen molecule. Helper T cell activation also requires longer duration of engagement with an antigen-presenting cell. [46] The activation of a resting helper T cell causes it to release cytokines that influence the activity of many cell types. Cytokine signals produced by helper T cells enhance the microbicidal function of macrophages and the activity of killer T cells. [5] In addition, helper T cell activation causes an upregulation of molecules expressed on the T cell's surface, such as CD40 ligand (also called CD154), which provide extra stimulatory signals typically required to activate antibody-producing B cells. CD154, also called CD40 ligand or CD40L is a protein that is primarily expressed on activated T cells and is a member of the TNF family of molecules [47]
γδ T cells
γδ T cells possess an alternative T cell receptor (TCR) as opposed to CD4+ and CD8+ (αβ) T cells and share the characteristics of helper T cells, cytotoxic T cells and NK cells. The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells that is in general responsible for recognizing Antigens bound The conditions that produce responses from γδ T cells are not fully understood. Like other 'unconventional' T cell subsets bearing invariant TCRs, such as CD1d-restricted Natural Killer T cells, γδ T cells straddle the border between innate and adaptive immunity. CD1d is a member of the CD1 (cluster of differentiation 1 family of Glycoproteins expressed on the surface of various human Antigen-presenting cells Natural killer T (NKT cells are a heterogeneous group of T cells that share properties of both T cells and natural killer (NK cells. [48] On one hand, γδ T cells are a component of adaptive immunity as they rearrange TCR genes to produce receptor diversity and can also develop a memory phenotype. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic V(DJ recombination is a mechanism of Genetic recombination that occurs in Vertebrates which randomly selects and assembles segments of Genes encoding On the other hand, the various subsets are also part of the innate immune system, as restricted TCR or NK receptors may be used as pattern recognition receptors. Pattern recognition receptors, or PRR s are Proteins expressed by cells of the Immune system to identify molecules associated with microbial Pathogens For example, large numbers of human Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted Vδ1+ T cells in epithelia will respond to stressed epithelial cells. Non-peptidic antigens are low molecular weight compounds that stimulate human Vγ9/Vδ2 T cells. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body [49]
B lymphocytes and antibodies
A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by [50] This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides. Proteolysis is the directed degradation ( digestion) of Proteins by cellular Enzymes called Proteases or by intramolecular digestion The B cell then displays these antigenic peptides on its surface MHC class II molecules. This combination of MHC and antigen attracts a matching helper T cell, which releases lymphokines and activates the B cell. Lymphokines are a subset of Cytokines that are produced by a type of Immune cell known as a Lymphocyte. [51] As the activated B cell then begins to divide, its offspring (plasma cells) secrete millions of copies of the antibody that recognizes this antigen. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Plasma cells (also called plasma B cells or plasmocytes) are cells of the Immune system that secrete large amounts of antibodies. Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance These antibodies circulate in blood plasma and lymph, bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. Antibodies can also neutralize challenges directly, by binding to bacterial toxins or by interfering with the receptors that viruses and bacteria use to infect cells. [52]CD20 antigen is also found on B lymphocytes. CD20 is a non- Glycosylated phosphoprotein expressed on the surface of all mature B-cells.
Alternative adaptive immune system
Although the classical molecules of the adaptive immune system (e. g. antibodies and T cell receptors) exist only in jawed vertebrates, a distinct lymphocyte-derived molecule has been discovered in primitive jawless vertebrates, such as the lamprey and hagfish. The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells that is in general responsible for recognizing Antigens bound A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Agnatha ( Greek, "no jaws" is a Paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata A lamprey (sometimes also called lamprey eel) is a Jawless fish with a toothed funnel-like sucking mouth Hagfish are marine Craniates of the class Myxini, also known as Hyperotreti. These animals possess a large array of molecules called variable lymphocyte receptors (VLRs) that, like the antigen receptors of jawed vertebrates, are produced from only a small number (one or two) of genes. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance These molecules are believed to bind pathogenic antigens in a similar way to antibodies, and with the same degree of specificity. An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response [53]
Immunological memory
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For more details on this topic, see Immunity (medical). Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion
When B cells and T cells are activated and begin to replicate, some of their offspring will become long-lived memory cells. Throughout the lifetime of an animal, these memory cells will remember each specific pathogen encountered and can mount a strong response if the pathogen is detected again. This is "adaptive" because it occurs during the lifetime of an individual as an adaptation to infection with that pathogen and prepares the immune system for future challenges. Immunological memory can either be in the form of passive short-term memory or active long-term memory.
Passive memory
Newborn infants have no prior exposure to microbes and are particularly vulnerable to infection. Several layers of passive protection are provided by the mother. During pregnancy, a particular type of antibody, called IgG, is transported from mother to baby directly across the placenta, so human babies have high levels of antibodies even at birth, with the same range of antigen specificities as their mother. Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female Immunoglobulin G ( IgG) is a Monomeric Immunoglobulin, built of two heavy chains γ and two light chains. The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation [54] Breast milk also contains antibodies that are transferred to the gut of the infant and protect against bacterial infections until the newborn can synthesize its own antibodies. Breast milk refers to the Milk produced by a mother to feed her baby [55] This is passive immunity because the fetus does not actually make any memory cells or antibodies--it only borrows them. Passive immunity is the transfer of active Humoral immunity in the form of readymade antibodies from one individual to another A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and This passive immunity is usually short-term, lasting from a few days up to several months. In medicine, protective passive immunity can also be transferred artificially from one individual to another via antibody-rich serum. Intravenous immunoglobulin (IVIG is a blood product administered Intravenously It contains the pooled IgG Immunoglobulins ( Antibodies Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended [56]
Active memory and immunization
Long-term active memory is acquired following infection by activation of B and T cells. Active immunity can also be generated artificially, through vaccination. Vaccination is the administration of Antigenic material (the Vaccine) to produce immunity to a disease The principle behind vaccination (also called immunization) is to introduce an antigen from a pathogen in order to stimulate the immune system and develop specific immunity against that particular pathogen without causing disease associated with that organism. Immunization, or immunisation, is the process by which an individual's Immune system becomes fortified against an agent (known as the An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response [5] This deliberate induction of an immune response is successful because it exploits the natural specificity of the immune system, as well as its inducibility. With infectious disease remaining one of the leading causes of death in the human population, vaccination represents the most effective manipulation of the immune system mankind has developed. [57][25]
Most viral vaccines are based on live attenuated viruses, while many bacterial vaccines are based on acellular components of micro-organisms, including harmless toxin components. A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease The attenuator plays an important regulatory role in prokaryotic cells because of the absence of the nucleus in Prokaryotic Organisms Non-cellular life is Life that exists without cells This term usually is applied to earth-based life and presumes the Phylogenetic classification A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low [5] Since many antigens derived from acellular vaccines do not strongly induce the adaptive response, most bacterial vaccines are provided with additional adjuvants that activate the antigen-presenting cells of the innate immune system and maximize immunogenicity. In Immunology, an adjuvant is an agent that may stimulate the Immune system and increase the response to a Vaccine, without having any specific Antigenic See also Antigen presentation An antigen-presenting cell ( APC) or accessory cell is a cell that displays foreign Antigen complexed Immunogenicity is the ability of a particular substance which is called the Antigen, to provoke an Immune response. [58]
Disorders of human immunity
The immune system is a remarkably effective structure that incorporates specificity, inducibility and adaptation. Failures of host defense do occur, however, and fall into three broad categories: immunodeficiencies, autoimmunity, and hypersensitivities.
Immunodeficiencies
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For more details on this topic, see Immunodeficiency. In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised
Immunodeficiencies occur when one or more of the components of the immune system are inactive. In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised The ability of the immune system to respond to pathogens is diminished in both the young and the elderly, with immune responses beginning to decline at around 50 years of age due to immunosenescence. Old age consists of ages nearing or surpassing the Average life span of Human beings and thus the end of the human life cycle. Immunosenescence refers to the gradual deterioration of the Immune system brought on by natural age advancement. [59][60] In developed countries, obesity, alcoholism, and drug use are common causes of poor immune function. The term developed country, or advanced country, is used to categorize countries with developed Economies in which the tertiary and quaternary sectors Obesity is a condition in which excess Body fat has accumulated to such an extent that health may be negatively affected Alcohol abuse, as described in the DSM-IV, is a psychiatric diagnosis describing the use of Alcoholic beverages despite negative consequences [60] However, malnutrition is the most common cause of immunodeficiency in developing countries. Malnutrition is a general term for a medical condition caused by an improper or insufficient diet. Developing countries are countries that haven't reached Western-style standards of democratic government free market economy industrialization social programs and human rights guaranties [60] Diets lacking sufficient protein are associated with impaired cell-mediated immunity, complement activity, phagocyte function, IgA antibody concentrations, and cytokine production. Immunoglobulin A ( IgA) is an Antibody playing a critical role in mucosal immunity Deficiency of single nutrients such as iron; copper; zinc; selenium; vitamins A, C, E, and B6; and folic acid (vitamin B9) also reduces immune responses. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 A vitamin is an Organic compound required as a Nutrient in tiny amounts by an Organism. Retinol (Afaxin, the animal form of Vitamin A, is a fat-soluble vitamin important in vision and Bone growth Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian Tocopherol, a class of chemical compounds of which many have Vitamin E activity describes a series of Organic compounds consisting of various methylated phenols Vitamin B6 is a water-soluble Vitamin. Pyridoxal phosphate (PLP is the active form and is a cofactor in many reactions of Amino acid metabolism including Folic acid (also known as Vitamin M and Folacin) and Folate (the Anionic form are forms of the water-soluble Vitamin B9 [60] Additionally, the loss of the thymus at an early age through genetic mutation or surgical removal results in severe immunodeficiency and a high susceptibility to infection. In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. [61]
Immunodeficiencies can also be inherited or 'acquired'. In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised [5] Chronic granulomatous disease, where phagocytes have a reduced ability to destroy pathogens, is an example of an inherited, or congenital, immunodeficiency. Chronic granulomatous disease (CGD is a diverse group of hereditary diseases in which certain cells of the Immune system have difficulty forming the reactive Phagocytes are cells that are found in the blood bone marrow and other tissues of Vertebrates. Primary immunodeficiencies are disorders in which part of the body's Immune system is missing or does not function properly AIDS and some types of cancer cause acquired immunodeficiency. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled [62][63]
Autoimmunity
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For more details on this topic, see Autoimmunity. Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues
Overactive immune responses comprise the other end of immune dysfunction, particularly the autoimmune disorders. Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues Here, the immune system fails to properly distinguish between self and non-self, and attacks part of the body. Under normal circumstances, many T cells and antibodies react with “self” peptides. [64] One of the functions of specialized cells (located in the thymus and bone marrow) is to present young lymphocytes with self antigens produced throughout the body and to eliminate those cells that recognize self-antigens, preventing autoimmunity. In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of [50]
Hypersensitivity
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For more details on this topic, see Hypersensitivity. Hypersensitivity (also called hypersensitivity reaction refers to undesirable (damaging discomfort-producing and sometimes fatal reactions produced by the normal immune system
Hypersensitivity is an immune response that damages the body's own tissues. Hypersensitivity (also called hypersensitivity reaction refers to undesirable (damaging discomfort-producing and sometimes fatal reactions produced by the normal immune system They are divided into four classes (Type I – IV) based on the mechanisms involved and the time course of the hypersensitive reaction. Type I hypersensitivity is an immediate or anaphylactic reaction, often associated with allergy. Anaphylaxis is an acute systemic (multi-system and severe Type I Hypersensitivity allergic reaction in humans and other Mammals Allergy is a disorder of the Immune system often also referred to as Atopy. Symptoms can range from mild discomfort to death. Type I hypersensitivity is mediated by IgE released from mast cells and basophils. In Biology, Immunoglobulin E ( IgE) is a class of Antibody (or Immunoglobulin " Isotype " that has only been found in A mast cell (or mastocyte) is a resident cell of several types of tissues and contains many granules rich in Histamine and Heparin [65] Type II hypersensitivity occurs when antibodies bind to antigens on the patient's own cells, marking them for destruction. This is also called antibody-dependent (or cytotoxic) hypersensitivity, and is mediated by IgG and IgM antibodies. Immunoglobulin G ( IgG) is a Monomeric Immunoglobulin, built of two heavy chains γ and two light chains. Immunoglobulin M, or IgM for short is a basic Antibody that is present on B cells It is the primary antibody against A and B [65] Immune complexes (aggregations of antigens, complement proteins, and IgG and IgM antibodies) deposited in various tissues trigger Type III hypersensitivity reactions. An immune complex is the combination of an Epitope with an Antibody directed against that epitope [65] Type IV hypersensitivity (also known as cell-mediated or delayed type hypersensitivity) usually takes between two and three days to develop. Type IV reactions are involved in many autoimmune and infectious diseases, but may also involve contact dermatitis (poison ivy). Contact dermatitis is a term for a Skin reaction resulting from exposure to Allergens (allergic contact dermatitis or irritants (irritant contact dermatitis These reactions are mediated by T cells, monocytes, and macrophages. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that [65]
Other mechanisms of host defense
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For more details on this topic, see Innate immune system#Other forms of innate immunity. Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner
It is likely that a multicomponent, adaptive immune system arose with the first vertebrates, as invertebrates do not generate lymphocytes or an antibody-based humoral response. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate [1] Many species, however, utilize mechanisms that appear to be precursors of these aspects of vertebrate immunity. Immune systems appear even in the most structurally-simple forms of life, with bacteria using a unique defense mechanism, called the restriction modification system to protect themselves from viral pathogens, called bacteriophages. The restriction modification system ( RM system) is used by Bacteria, and perhaps other prokaryotic organisms to protect themselves from foreign DNA This article is about a biological infectious particle for other uses see Phage (disambiguation. [66]
Pattern recognition receptors are proteins used by nearly all organisms to identify molecules associated with pathogens. Pattern recognition receptors, or PRR s are Proteins expressed by cells of the Immune system to identify molecules associated with microbial Pathogens Antimicrobial peptides called defensins are an evolutionarily conserved component of the innate immune response found in all animals and plants, and represent the main form of invertebrate systemic immunity. Antimicrobial peptides (also called host defence peptides are an evolutionarily conserved component of the innate immune response and are found among all classes of life An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion [1] The complement system and phagocytic cells are also used by most forms of invertebrate life. The complement system is a Biochemical cascade that helps clear Pathogens from an organism Ribonucleases and the RNA interference pathway are conserved across all eukaryotes, and are thought to play a role in the immune response to viruses. Ribonuclease, abbreviated commonly as RNase, is a Nuclease that catalyzes the degradation of RNA into smaller components RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex [67]
Unlike animals, plants lack phagocytic cells, and most plant immune responses involve systemic chemical signals that are sent through a plant. [68] When a part of a plant becomes infected, the plant produces a localized hypersensitive response, whereby cells at the site of infection undergo rapid apoptosis to prevent the spread of the disease to other parts of the plant. The hypersensitive response (HR is a mechanism used by Plants, to prevent the spread of Infection by Microbial Pathogens The HR is characterized Systemic acquired resistance (SAR) is a type of defensive response used by plants that renders the entire plant resistant to a particular infectious agent. In plants systemic acquired resistance (SAR is a "whole-plant" resistance response that occurs following an earlier localized exposure to a Pathogen. There are a number of lines of defence against pests (that is those animals that cause damage to the plants we grow and diseases in the organic garden, principle [68] RNA silencing mechanisms are particularly important in this systemic response as they can block virus replication. RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific [69]
Tumor immunology
- Further information: Cancer immunology
Another important role of the immune system is to identify and eliminate tumors. See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic The transformed cells of tumors express antigens that are not found on normal cells. An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response To the immune system, these antigens appear foreign, and their presence causes immune cells to attack the transformed tumor cells. The antigens expressed by tumors have several sources;[71] some are derived from oncogenic viruses like human papillomavirus, which causes cervical cancer,[72] while others are the organism's own proteins that occur at low levels in normal cells but reach high levels in tumor cells. Oncogenesis is the process of Malignant transformation leading to the formation of a tumor ( Tumorigenesis) A human papillomavirus ( HPV) is a Papillomavirus that infects the skin and Mucous membranes of Humans Approximately 130 HPV types have been Cervical cancer is Malignant Cancer of the Cervix uteri or cervical area One example is an enzyme called tyrosinase that, when expressed at high levels, transforms certain skin cells (e. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Tyrosinase (monophenol monooxygenase ( CAS number: 9002-10-2 is an Enzyme that catalyses the Oxidation of Phenols (such as g. melanocytes) into tumors called melanomas. Melanocytes are cells located in the bottom layer (the Stratum basale) of the skin's epidermis and in the middle layer of the eye (the Uvea) Melanoma is a Malignant Tumor of Melanocytes which are found predominantly in skin but also in the Bowel and the Eye (see [73][74] A third possible source of tumor antigens are proteins normally important for regulating cell growth and survival, that commonly mutate into cancer inducing molecules called oncogenes. The term cell growth is used in two different ways in Biology. An oncogene is a protein encoding Gene, which — when deregulated — participates in the onset and development of Cancer. [71][75][76]
The main response of the immune system to tumors is to destroy the abnormal cells using killer T cells, sometimes with the assistance of helper T cells. [74][77] Tumor antigens are presented on MHC class I molecules in a similar way to viral antigens. This allows killer T cells to recognize the tumor cell as abnormal. [78] NK cells also kill tumorous cells in a similar way, especially if the tumor cells have fewer MHC class I molecules on their surface than normal; this is a common phenomenon with tumors. [79] Sometimes antibodies are generated against tumor cells allowing for their destruction by the complement system. The complement system is a Biochemical cascade that helps clear Pathogens from an organism [75]
Clearly, some tumors evade the immune system and go on to become cancers. [80] Tumor cells often have a reduced number of MHC class I molecules on their surface, thus avoiding detection by killer T cells. [78] Some tumor cells also release products that inhibit the immune response; for example by secreting the cytokine TGF-β, which suppresses the activity of macrophages and lymphocytes. Transforming growth factor beta (TGF-β controls proliferation, Cellular differentiation, and other functions in most cells Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that A lymphocyte is a type of White blood cell in the Vertebrate Immune system. [81] In addition, immunological tolerance may develop against tumor antigens, so the immune system no longer attacks the tumor cells. Immune or immunological tolerance is the process by which the Immune system does not attack an Antigen. [80]
Paradoxically, macrophages can promote tumor growth [82] when tumor cells send out cytokines that attract macrophages which then generate cytokines and growth factors that nurture tumor development. In addition, a combination of hypoxia in the tumor and a cytokine produced by macrophages induces tumor cells to decrease production of a protein that blocks metastasis and thereby assists spread of cancer cells. Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets,
Physiological regulation
Hormones can act as immunomodulators, altering the sensitivity of the immune system. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body An immunomodulator is a drug used for its effect on the Immune system. For example, female sex hormones are known immunostimulators of both adaptive[83] and innate immune responses. Sex steroids, also known as gonadal steroids, are Steroid hormones that interact with Vertebrate Androgen or Estrogen receptors Immunostimulators are substances (drugs and nutrients that stimulate the Immune system by inducing activation or increasing activity of any of its components [84] Some autoimmune diseases such as lupus erythematosus strike women preferentially, and their onset often coincides with puberty. Systemic lupus erythematosus ( SLE or lupus,) is a chronic autoimmune disease that can be fatal though with recent medical advances fatalities are becoming By contrast, male sex hormones such as testosterone seem to be immunosuppressive. Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries Immunosuppression involves an act that reduces the activation or Efficacy of the Immune system. [85] Other hormones appear to regulate the immune system as well, most notably prolactin, growth hormone and vitamin D. Prolactin ( PRL) or Luteotropic hormone ( LTH) is a Peptide hormone primarily associated with Lactation. Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or [86][87] It is conjectured that a progressive decline in hormone levels with age is partially responsible for weakened immune responses in aging individuals. [88] Conversely, some hormones are regulated by the immune system, notably thyroid hormone activity. The thyroid hormones, Thyroxine ( T4) and Triiodothyronine ( T3) are Tyrosine -based Hormones produced [89]
The immune system is enhanced by sleep and rest,[90] and is impaired by stress. [91]
Diet may affect the immune system; for example, fresh fruits, vegetables, and foods rich in certain fatty acids may foster a healthy immune system. The term fruit has different meanings dependent on context and the term is not synonymous in Food preparation and Biology. The term " vegetable " generally means the edible parts of Plants The definition of the word is traditional rather than Scientific, however In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which [92] Likewise, fetal undernourishment can cause a lifelong impairment of the immune system. Prenatal development is the process in which an embryo or fetus (or foetus) gestates during Pregnancy, from fertilization [93] In traditional medicine, some herbs are believed to stimulate the immune system, such as echinacea, licorice, ginseng, astragalus, sage, garlic, elderberry, shiitake and lingzhi mushrooms, and hyssop, as well as honey. The term traditional medicine ( Indigenous medicine or folk medicine) describes medical knowledge systems which developed over centuries within various societies Echinacea, commonly called Purple Coneflower, is a genus of nine species of Herbaceous plants in the family Asteraceae. Liquorice (UK or licorice (US (see spelling differences;, or) is the root of Glycyrrhiza glabra, from which a sweet flavour can be extracted Ginseng refers to species within Panax, a genus of 11 species of slow-growing Perennial plants with fleshy roots in the family Araliaceae. Astragalus ( As-trá-ga-lus) is a large genus of about 2000 species of Herbs and small Shrubs belonging to the Legume Common sage ( Salvia officinalis) is a small perennial Evergreen Subshrub, with woody stems grayish leaves and blue to purplish flowers Allium sativum L, commonly known as garlic, is a species in the Onion family Alliaceae. Sambucus ( Elder or Elderberry) is a genus of between 5 and 30 species of Shrubs or small Trees (two species Herbaceous) The shiitake ( Lentinula edodes) is an Edible mushroom native to East Asia, which is cultivated and consumed in many Asian countries as well as being dried Língzhī (traditional Chinese 靈芝; simplified Chinese 灵芝; Japanese reishi; Korean yeongji, hangul 영지 is the name for one Hyssopus can also refer to a genus of Hymenopteran Insects of the family Eulophidae. Honey is a sweet and Viscous fluid produced by Honey bees (and some other species and derived from the nectar of Flowers According to the Studies have suggested that such herbs can indeed stimulate the immune system,[94] although their mode of action is complex and difficult to characterize.
Manipulation in medicine
The immune response can be manipulated to suppress unwanted responses resulting from autoimmunity, allergy, and transplant rejection, and to stimulate protective responses against pathogens that largely elude the immune system (see immunization). For a list of immunosuppressive drugs see the Transplant rejection page. Dexamethasone is a potent synthetic member of the glucocorticoid class of Steroid Hormones It acts as an Anti-inflammatory and immunosuppressant Transplant rejection occurs when a transplanted organ or tissue fails to be accepted by the body of the transplant recipient Immunosuppressive drugs are used to control autoimmune disorders or inflammation when excessive tissue damage occurs, and to prevent transplant rejection after an organ transplant. For a list of immunosuppressive drugs see the Transplant rejection page. Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens Transplant rejection occurs when a transplanted organ or tissue fails to be accepted by the body of the transplant recipient [25][95]
Anti-inflammatory drugs are often used to control the effects of inflammation. Anti-inflammatory refers to the property of a substance or treatment that reduces Inflammation. The glucocorticoids are the most powerful of these drugs; however, these drugs can have many undesirable side effects (e. Glucocorticoids (GC are a class of Steroid hormones characterised by an ability to bind with the glucocorticoid receptor ( GR) and trigger similar effects g. , central obesity, hyperglycemia, osteoporosis) and their use must be tightly controlled. Central obesity, the "apple-shaped" Obesity commonly referred to as belly fat, is the accumulation of Visceral fat ( fat deposited Hyperglycemia, hyperglycaemia, or high blood sugar is a condition in which an excessive amount of Glucose circulates in the Blood plasma Osteoporosis is a Disease of Bone that leads to an increased risk of fracture. [96] Therefore, lower doses of anti-inflammatory drugs are often used in conjunction with cytotoxic or immunosuppressive drugs such as methotrexate or azathioprine. Cytotoxicity is the quality of being toxic to cells Examples of toxic agents are a Chemical substance, an Immune cell or some types of Venom For a list of immunosuppressive drugs see the Transplant rejection page. Azathioprine is an immunosuppressant used in Organ transplantation Autoimmune disease such as Rheumatoid arthritis and Pemphigus or inflammatory Cytotoxic drugs inhibit the immune response by killing dividing cells such as activated T cells. Chemotherapy, in its most general sense refers to treatment of disease by chemicals that kill cells specifically those of micro-organisms or Cancer. However, the killing is indiscriminate and other constantly dividing cells and their organs are affected, which causes toxic side effects. [95] Immunosuppressive drugs such as cyclosporin prevent T cells from responding to signals correctly by inhibiting signal transduction pathways. Ciclosporin (ˌsaɪkləˈspɔrən cyclosporine ( USAN) or cyclosporin (former BAN) is an Immunosuppressant drug widely In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another [97]
Larger drugs (>500 Da) can provoke a neutralizing immune response, particularly if the drugs are administered repeatedly, or in larger doses. The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express This limits the effectiveness of drugs based on larger peptides and proteins (which are typically larger than 6000 Da). In some cases, the drug itself is not immunogenic, but may be co-administered with an immunogenic compound, as is sometimes the case for Taxol. Paclitaxel is a Mitotic inhibitor used in Cancer Chemotherapy. Computational methods have been developed to predict the immunogenicity of peptides and proteins, which are particularly useful in designing therapeutic antibodies, assessing likely virulence of mutations in viral coat particles, and validation of proposed peptide-based drug treatments. Early techniques relied mainly on the observation that hydrophilic amino acids are overrepresented in epitope regions than hydrophobic amino acids;[98] however, more recent developments rely on machine learning techniques using databases of existing known epitopes, usually on well-studied virus proteins, as a training set. Hydrophile, from the Greek (hydros "water" and φιλια (philia "friendship" refers to a physical property of a Molecule In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this An epitope, also known as antigenic determinant, is the part of a Macromolecule that is recognized by the Immune system, specifically by antibodies In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of Machine learning is a subfield of Artificial intelligence that is concerned with the design and development of Algorithms and techniques that allow computers to "learn" In Artificial intelligence, a training set consists of an Input vector and an answer vector and is used together with a Supervised learning [99] A publicly accessible database has been established for the cataloguing of epitopes from pathogens known to be recognizable by B cells. [100] The emerging field of bioinformatics-based studies of immunogenicity is referred to as immunoinformatics. Bioinformatics is the application of information technology to the field of molecular biology [101]
Manipulation by pathogens
The success of any pathogen is dependent on its ability to elude host immune responses. Therefore, pathogens have developed several methods that allow them to successfully infect a host, while evading immune-mediated destruction. [102] Bacteria often overcome physical barriers by secreting enzymes that digest the barrier — for example, by using a type II secretion system. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance [103] Alternatively, using a type III secretion system, they may insert a hollow tube into the host cell, which provides a direct conduit for proteins to move from the pathogen to the host; the proteins transported along the tube are often used to shut down host defenses. Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance [104]
An evasion strategy used by several pathogens to circumvent the innate immune system is intracellular replication (also called intracellular pathogenesis). Not to be confused with Intercellular, meaning "between cells" The term pathogenesis means step by step development of a disease due to a series of changes in the structure and /or function of a cell/tissue/organ being caused by a microbial, chemical or physical Here, a pathogen spends a majority of its life-cycle inside host cells, where it is shielded from direct contact with immune cells, antibodies and complement. Some examples of intracellular pathogens include viruses, the food poisoning bacterium Salmonella and the eukaryotic parasites that cause malaria (Plasmodium falciparum) and leishmaniasis (Leishmania spp.). Foodborne illness (also foodborne disease) is any Illness resulting from the consumption of food The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Salmonella is a Genus of rod-shaped Gram-negative enterobacteria that causes Typhoid fever, Paratyphoid fever Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including Plasmodium falciparum is a Protozoan Parasite, one of the species of Plasmodium that cause Malaria in humans Leishmaniasis is a Disease caused by Protozoan Parasites that belong to the genus Leishmania and is transmitted by the bite of certain Leishmania is a Genus of Trypanosome Protozoa, and is the Parasite responsible for the disease Leishmaniasis. Other bacteria, such as Mycobacterium tuberculosis, live inside a protective capsule that prevents lysis by complement. Mycobacterium tuberculosis is the Bacterium that causes most cases of Tuberculosis. Lysis ( Greek, lysis from lyein = to separate refers to the death of a cell by breaking of the cellular membrane often by viral or osmotic [105] Many pathogens secrete compounds that diminish or misdirect the host's immune response. [102] Some bacteria form biofilms to protect themselves from the cells and proteins of the immune system. A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface Such biofilms are present in many successful infections, e. g. , the chronic Pseudomonas aeruginosa and Burkholderia cenocepacia infections characteristic of cystic fibrosis. Pseudomonas aeruginosa is a Gram-negative, aerobic, rod-shaped Bacterium with unipolar motility. Burkholderia cenocepacia is a Gram-negative bacteria that is common in the environment and may cause disease in plants Cystic fibrosis (also known as CF, mucoviscoidosis, or mucoviscidosis) is a hereditary disease affecting the exocrine (mucus glands of the lungs [106] Other bacteria generate surface proteins that bind to antibodies, rendering them ineffective; examples include Streptococcus (protein G), Staphylococcus aureus (protein A), and Peptostreptococcus magnus (protein L). Streptococcus is a Genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the Staphylococcus aureus (ˌstæfɨləˈkɒkəs ˈɔriəs literally "Golden Cluster Seed" and also known as golden staph) is the most common cause of Peptostreptococcus is a Genus of anaerobic, Gram-positive, non- spore forming bacteria. [107]
The mechanisms used by viruses to evade the adaptive immune system are more complicated. The simplest approach is to rapidly change non-essential epitopes (amino acids and/or sugars) on the invader's surface, while keeping essential epitopes concealed. An epitope, also known as antigenic determinant, is the part of a Macromolecule that is recognized by the Immune system, specifically by antibodies In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this HIV, for example, regularly mutates the proteins on its viral envelope that are essential for entry into its host target cell. Many Viruses (eg influenza and many animal viruses have viral envelopes covering their protein Capsids The envelopes are typically derived from portions of These frequent changes in antigens may explain the failures of vaccines directed at these proteins. A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease [108] Masking antigens with host molecules is another common strategy for avoiding detection by the immune system. In HIV, the envelope that covers the viron is formed from the outermost membrane of the host cell; such "self-cloaked" viruses make it difficult for the immune system to identify them as "non-self". A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable [109]
History of immunology
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For more details on this topic, see History of immunology. Timeline of immunology: 1718 - Lady Mary Wortley Montagu, the wife of the British ambassador to Constantinople observed the positive effects of Variolation
Immunology is a science that examines the structure and function of the immune system. Paul Ehrlich ( March 14, 1854 &ndash August 20, 1915) was a German Scientist who won the 1908 Nobel Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with It originates from medicine and early studies on the causes of immunity to disease. Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the The earliest known mention of immunity was during the plague of Athens in 430 BC. The Plague of Athens was a devastating Epidemic which hit the City-state of Athens in ancient Greece during the second year of the Peloponnesian Thucydides noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time. Thucydides ( C 460 BC &ndash C 395 BC) ( Greek Θουκυδίδης Thoukydídēs) was a Greek [110] This observation of acquired immunity was later exploited by Louis Pasteur in his development of vaccination and his proposed germ theory of disease. Louis Pasteur (27 December 1822 – 28 September 1895 a French Chemist and Microbiologist, is best known for remarkable breakthroughs in the causes and Vaccination is the administration of Antigenic material (the Vaccine) to produce immunity to a disease The germ theory, also called the pathogenic theory of medicine, is a Theory that proposes that Microorganisms are the cause of many Diseases. [111] Pasteur's theory was in direct opposition to contemporary theories of disease, such as the miasma theory. The miasmatic theory of disease held that Diseases such as Cholera or the Black Death were caused by a miasma (Greek language "pollution" It was not until Robert Koch's 1891 proofs, for which he was awarded a Nobel Prize in 1905, that microorganisms were confirmed as the cause of infectious disease. Heinrich Hermann Robert Koch ( December 11 1843 – May 27 1910) was a German Physician. Koch's postulates are four criteria designed to establish a causal relationship between a causative Microbe and a Disease. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually An infectious disease is a clinically evident Disease resulting from the presence of Pathogenic microbial agents including Pathogenic viruses Pathogenic [112] Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed. Yellow fever (also called yellow jack, black vomit or sometimes American Plague) is an acute viral disease Major Walter Reed, MD, ( September 13 1851 - November 23 1902) was a U [113]
Immunology made a great advance towards the end of the 19th century, through rapid developments, in the study of humoral immunity and cellular immunity. The Humoral Immune Response (HIR is the aspect of immunity that is mediated by secreted Antibodies (as opposed to Cell-mediated immunity which involves Cell-mediated immunity is an Immune response that does not involve Antibodies or complement but rather involves the activation of Macrophages [114] Particularly important was the work of Paul Ehrlich, who proposed the side-chain theory to explain the specificity of the antigen-antibody reaction; his contributions to the understanding of humoral immunity were recognized by the award of a Nobel Prize in 1908, which was jointly awarded to the founder of cellular immunology, Elie Metchnikoff. Paul Ehrlich ( March 14, 1854 &ndash August 20, 1915) was a German Scientist who won the 1908 Nobel Side-chain theory ( German, Seitenkettentheorie) is a Theory proposed by Paul Ehrlich (1854&ndash1915 to explain the Immune response Ilya Ilyich Mechnikov (Илья Ильич Мечников ( May 16 1845 – July 15 1916) was a Russian microbiologist [115]
See also
- Clonal selection
- Epitope
- Hapten
- Human physiology
- Immunostimulator
- Monoclonal antibodies
- Original antigenic sin
- Polyclonal antibodies
- Tumor antigens
- Immune system receptors
- Polyclonal response
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External links
- How Your Immune System Works - from HowStuffWorks
- Immune System - from the University of Hartford
- Immunobiology; Fifth Edition – Online version of the textbook by Charles Janeway (Advanced undergraduate/graduate level)
- Immunology - BioMed Central (free content) scientific journal
- The Inner Life of a Cell - Rendering of the inner functions of the human body
- The Microbial World - Animal defenses against microbes - Chapter in on-line microbiology textbook
- Microbiology and Immunology On-Line Textbook - from the University of South Carolina School of Medicine
- Plant Immunity - Institute of Biochemical Plant Pathology at the GSF-National Research Center for Environment and Health
Events 871 - Battle of Ashdown - Ethelred of Wessex defeats a Danish invasion army Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The University of Hartford, often called UHA or UHart, was founded in 1877 and is a private independent and nonsectarian Charles Alderson Janeway Jr (1943-2003 was a noted Immunologist. BioMed Central ( BMC) is a UK -based for-profit scientific publisher specialising in Open access publication This article is about the University of South Carolina in Columbia
Dictionary
immune system
-noun
- (anatomy, immunology) The system that differentiates self from non-self and protects the body from foreign substances and pathogenic organisms by producing an immune response. It includes organs such as the thymus, the spleen and lymph nodes; tissue such as bone marrow, and lymphoid tissues such as the tonsils; cells such as lymphocytes including the B cells and T cells, and cell products such as antibodies.
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