Note that some complexity is omitted from the diagram. Lymphocytes come from "Lymphoid" line, whereas granulocytes, monocytes, megakaryocytes, and erythrocytes come from "Myeloid" line. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Granulocytes are a category of White blood cells characterised by Monocyte is a type of Leukocyte, part of the Human body 's Immune system. The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Among myeloid cells, granulocytes and monocytes have a common precursor, "CFU-GM". Granulocytes are a category of White blood cells characterised by Monocyte is a type of Leukocyte, part of the Human body 's Immune system.

Hematopoietic stem cells (HSCs) are stem cells that give rise to all the blood cell types including myeloid (monocytes and macrophages, neutrophils, basophils, eosinophils, erythrocytes, megakaryocytes/platelets, dendritic cells), and lymphoid lineages (T-cells, B-cells, NK-cells). Stem cells are cells found in most if not all multi-cellular Organisms. The term myeloid suggests an origin in the Bone marrow or Spinal cord, or a resemblance to the marrow or spinal cord 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 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 Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally Platelets, or Thrombocytes, are small cytoplasmic bodies derived from cells They circulate in the Blood of Mammals and are involved Dendritic cells (DCs are Immune cells and form part of the Mammalian Immune system. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. 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 Natural killer cells (or NK cells) are a type of Cytotoxic Lymphocyte that constitute a major component of the Innate immune system. The definition of hematopoietic stem cells has undergone considerable revision in the last two decades. The hematopoietic tissue contains cells with long-term and short-term regeneration capacities and committed multipotent, oligopotent, and unipotent progenitors. Multipotent Progenitor cells can give rise to several other cell types but those types are limited in number Oligopotency is the ability of Progenitor cells to differentiate into one or many Cell types. In Mathematics, a unipotent element r of a ring R is one such that r  &minus 1 is a Nilpotent element, in Recently, long-term transplantation experiments point toward a clonal diversity model of hematopoietic stem cells. Here, the HSC compartment consists of a fixed number of different types of HSC, each with epigenetically preprogrammed behavior. In Biology, the term epigenetics refers to changes in Gene expression caused by mechanisms other than changes in the underlying DNA sequence This contradicts older models of HSC behavior, which postulated a single type of HSC that can be continuously molded into different subtypes of HSCs. HSCs constitute 1:10. 000 of cells in myeloid tissue. Myeloid tissue is a Biologic tissue with the ability to perform Hematopoiesis.

Source

Sketch of bone marrow and its cells

HSCs are found in the bone marrow of adults, which includes femurs, hip, ribs, sternum, and other bones. The femur is the thigh bone In Humans, it is the longest, most voluminous and strongest Bone. In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. The sternum (from Greek στέρνον sternon, "chest" or breastbone) is a long flat Bone located in the center of the thorax (chest Cells can be obtained directly by removal from the hip using a needle and syringe, or from the blood following pre-treatment with cytokines, such as G-CSF (granulocyte colony-stimulating factors), that induce cells to be released from the bone marrow compartment. Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular Other sources for clinical and scientific use include umbilical cord blood, placenta, molilized peripheral blood. In placental Mammals the umbilical cord (also called the birth cord or funiculus umbilicalis) is the connecting cord from the developing Embryo The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation For experimental purposes, fetal liver, fetal spleen, and AGM (Aorta-gonad-mesonephros) of animals are also useful sources of HSCs.

Functional Characteristics

Multipotency and self-renewal

As stem cells, they are defined by their ability to form multiple cell types (multipotency) and their ability to self-renew.

It is known that a small number of HSCs can expand to generate a very large number of progeny HSCs. This phenomenon is used in bone marrow transplant when a small number of HSCs reconstitute the hematopoietic system. This indicates that, at least during bone marrow transplant, symmetrical cell divisions that give two progeny HSCs must occur, as expansion in HSC numbers seen during bone marrow transplant cannot occur in any other way.

Stem cell self-renewal is thought to occur in the stem cell niche in the bone marrow, and it is reasonable to assume that key signals present in this niche will be important in self-renewal. There is much interest in the environmental and molecular requirements for HSC self-renewal, as understanding the ability of HSC to replenish themselves will eventually allow the generation of expanded populations of HSC ex vivo that can be used therapeutically.

Lineage-Bias

Using limiting dilution strategies combined with other streamlined experimental and statistical methods for examining HSCs at the clonal level, it was shown that HSCs fall into three distinct lineage-bias^{[1] [2] [3]} clusters. These are quantitatively defined by the ratio ρ of lymphoid to myeloid cells that HSC generate upon differentiation (which makes ρ a peripheral predictor for the clonal association of a reconstituted hematopoietic system). Balanced HSCs repopulate peripheral white blood cells in the same ratio of myeloid to lymphoid cells as seen in unmanipulated mice (on average about 15% myeloid and 85% lymphoid cells, or 3≤ρ≤10). Myeloid-biased (My-bi) HSC give rise to too few lymphocytes resulting in ratios 0<ρ<3, whereas lymphoid-biased (Ly-bi) HSC generate too few myeloid cells, which results in lymphoid-to-myeloid ratios of 10<ρ<oo. All three types are normal HSC in that they have self-renewal capacity and can regenerate all hematopietic lineages (pluripotency). What is striking to note is that the lineage-bias is preserved through multiple rounds of serial transplantation: Balanced HSC self-renew to give rise to daughter HSC that are also balanced, My-bi HSC give rise to My-bi daughter HSC, and Ly-bi produce Ly-bi daughter HSC. There is no precursor-progeny relationship between the three types of HSC and they do not represent stages of differentiation. Rather, these are three classes of HSC, each with an epigenetically-fixed differentiation program. In Biology, the term epigenetics refers to changes in Gene expression caused by mechanisms other than changes in the underlying DNA sequence

Functional Assays

• Cobble stone area-forming Cell (CAFC) assay: This is a cell culture based empirical assay. When plated onto a confluent culture of stromal feeder layer, a fraction of HSCs creep between the gaps (even though the stromal cells are touching each other) and eventually settle between the stromal cells and the substratum (here the dish surface) or trapped in the cellular processes between the stromal cells. Emperipolesis is the in vivo phenomenon in which one cell is completely engulfed into another (e. g. , thymocytes into thymic nurse cells); on the other hand, when in vitro, lymphoid lineage cells creep beneath nurse-like cells, the process is called pseudoemperipolesis. Thymocytes are T cell precursors which develop in the Thymus. In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. The term nurse cell is used in several unrelated ways in different scientific fields Human physiology Nurse cells are specialized macrophages residing in the bone marrow This similar phenomeonon is more commonly known in HSC field by the cell culture terminology cobble stone area-forming cells (CAFC), which means areas of cluster of cells that look dull cobblestone-like under phase contrast microscopy, compared to the other HSCs, which are refractile. Cobblestones are stones that were frequently used in the pavement of early Streets "Cobblestone" is derived from the very old English word "cob" This happens because the cells that are floating loosely on top of the stromal cells are spherical and thus refractile. However, the cells that creep beneath the stromal cells are flattened and thus not refractile. The mechanism of pseudoemperipolesis is only recently coming to light. It may be mediated by interaction through CXCR4 (CD184) the receptor for CXC Chemokines (e. CXCR4, (a '''CXC''' chemokine '''R'''eceptor) also called fusin, is an alpha- Chemokine receptor specific for stromal-derived-factor-1 ( SDF-1 g. , SDF1) and α4β1 integrins. SDF-1 ( Stromal cell -derived factor-1 is small Cytokine belonging to the Chemokine family that is officially designated Chemokine (C-X-C motif Integrin alpha4beta1 ( Very Late Antigen-4) is an Integrin Dimer. Integrins are Cell surface receptors that interact with the Extracellular matrix (ECM and mediate various intracellular signals. ^[4].

Mobility

HSCs have a higher potential than other immature blood cells to pass the bone marrow barrier, and thus may travel in the blood from the bone marrow in one bone to another bone. 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 If they settle in the thymus they'll develop into T cells. In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. In the case of fetuses and other extramedullary hematopoiesis HSCs may also settle in the liver or spleen and develop. Haematopoiesis (from Ancient Greek haima blood poiesis to make (or hematopoiesis in the United States sometimes also haemopoiesis or The liver is a vital organ in the human body and is present in Vertebrates and some other animals The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red

This ability is the reason why HSCs may be harvested directly from the blood.

Physical characteristics

With regard to morphology, hematopoietic stem cells resemble lymphocytes. They are non-adherent, and rounded, with a rounded nucleus and low cytoplasm-to-nucleus ratio. Since PHSC cannot be isolated as a pure population, it is not possible to identify them in a microscope. The above description is based on the morphological characteristics of a heterogeneous population, of which PHSC are a component.

Markers

In reference to phenotype, hematopoeitic stem cells are identified by their small size, lack of lineage (lin) markers, low staining (side population) with vital dyes such as rhodamine 123 (rhodamine^DULL, also called rho^lo) or Hoechst 33342, and presence of various antigenic markers on their surface, many of which belong to the cluster of differentiation series, like: CD34, CD38, CD90, CD133, CD105, CD45 and also c-kit- the receptor for stem cell factor. The cluster of differentiation (often abbreviated as CD) is a protocol used for the identification and investigation of Cell surface molecules present on Leukocytes CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body CD38 ( Cluster of differentiation 38 is a Glycoprotein found on the surface of many immune cells ( White blood cells, including CD4 + Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD133 is a Glycoprotein also known in humans and rodents as Prominin 1 (PROM1 Endoglin is a type I membrane Glycoprotein located on cell surfaces and is part of the TGF beta receptor complex In Immunology, the CD45 Antigen (CD stands for Cluster of differentiation) is a Protein which was originally called leukocyte common antigen CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types Stem cell factor ( SCF) otherwise known as KIT ligand or Steel factor,is a Cytokine which binds CD117 (c-Kit The hematopoietic stem cells are negative for the markers that are used for detection of lineage commitment, and are, thus, called Lin-; and, during their purification by FACS, a bunch of up to 14 different mature blood-lineage marker, e. Flow cytometry is a technique for counting examining and sorting microscopic particles suspended in a stream of fluid g. , CD13 & CD33 for myeloid, CD71 for erythroid, CD19 for B cells, CD61 for megakaryocytic, etc. Alanine aminopeptidase ( is an Enzyme that is used as a Biomarker to detect damage to the Kidneys and that may be used to help diagnose certain kidney CD33 is a Transmembrane receptor expressed on cells of monocytic / Myeloid lineage Transferrin receptor (p90 CD71, ( C luster of D ifferentiation 71) also known as TFRC, is a human Gene. CD19 ( C luster of D ifferentiation 19) is a human Protein encoded by the Gene. Integrin beta 3 (platelet glycoprotein IIIa antigen CD61, also known as ITGB3, is a human Gene. for humans; and, B220 (murine CD45) for B cells, Mac-1 (CD11b/CD18) for monocytes, Gr-1 for Granulocytes, Ter119 for erythroid cells, Il7Ra, CD3, CD4, CD5, CD8 for T cells, etc. In Immunology, the CD45 Antigen (CD stands for Cluster of differentiation) is a Protein which was originally called leukocyte common antigen In Immunology, the CD45 Antigen (CD stands for Cluster of differentiation) is a Protein which was originally called leukocyte common 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 Macrophage-1 antigen (or integrin alphaMbeta2) is a Complement receptor ("CR3" consisting of CD11b and CD18. Integrin alpha M (ITGAM is one protein subunit that forms the Heterodimeric Integrin alpha-M beta-2 (αMβ2 molecule also known as macrophage-1 Integrin beta 2 (complement component 3 receptor 3 and 4 subunit, also known as CD18 or ITGB2, is a human Gene. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Granulocytes are a category of White blood cells characterised by CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, CD8 ( Cluster of differentiation 8 is a transmembrane Glycoprotein that serves as a Co-receptor for the T cell receptor (TCR T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. for mice) antibodies are used as a mixture to deplete the lin+ cells or late multipotent progenitors (MPP)s.

There are many differences between the human and mice hematopoietic cell markers for the commonly-accepted type of hematopoietic stem cells. [1].

• Mouse HSC : CD34^lo/-, SCA-1⁺ , Thy1.1^+/lo, CD38⁺, C-kit⁺, lin^-
• Human HSC : CD34⁺, CD59⁺, Thy1/CD90⁺,CD38^lo/-, C-kit/CD117⁺, lin^-

However, not all stem cells are covered by these combinations that nonetheless have become popular. CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD38 ( Cluster of differentiation 38 is a Glycoprotein found on the surface of many immune cells ( White blood cells, including CD4 + CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Protectin a complement regulatory protein, also known as Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD38 ( Cluster of differentiation 38 is a Glycoprotein found on the surface of many immune cells ( White blood cells, including CD4 + CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types In fact, even in humans, there are hematopoietic stem cells that are CD34^-/CD38^-. CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body CD38 ( Cluster of differentiation 38 is a Glycoprotein found on the surface of many immune cells ( White blood cells, including CD4 + ^[5][6]. Also some later studies suggested that earliest stem cells may lack c-kit on the cell surface^[7]. For human HSCs use of CD133 was one step ahead as both CD34⁺ and CD34^- HSCs were CD133⁺. CD133 is a Glycoprotein also known in humans and rodents as Prominin 1 (PROM1 CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body CD133 is a Glycoprotein also known in humans and rodents as Prominin 1 (PROM1

Traditional purification method used to yield a reasonable purity level of mouse hematopoietic stem cells, in general, requires a large(~10-12) battery of markers, most of which were surrogate markers with little functional significance, and thus partial overlap with the stem cell populations and sometimes other closely-related cells that are not stem cells. Also, some of these markers 9eg Thy1) are not conserved across mouse species, and use of markers like CD34^- for HSC purification requires mice to be at least 8 weeks old. Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Alternative methods that could give rise to similar or better harvest of stem cells is a hot area of research and are presently emerging. One such method uses a signature of SLAM family of cell surface molecules. SLAM (Signaling lymphocyte activation molecule) family is a group of >10 molecules whose genes are mostly located tandemly in a single locus on chromosome 1 (mouse), all belonging to a subset of immunoglobulin gene superfamily, and originally thought to be involved in T-cell stimulation. This family includes CD48, CD150, CD244, etc. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD244 ( C luster of D ifferentiation 244 is a human Protein encoded by the Gene. , CD150 being the founding member, and, thus, also called slamF1 ie SLAM family member 1.

The signature SLAM code for the hemapoietic higherchy are:

• Hematopoietic stem cells (HSC) : CD150⁺CD48^-CD244^-
• Multipotent progenitor cells (MPPs) : CD150^-CD48^-CD244⁺
• Lineage-restricted progenitor cells (LRPs) : CD150^-CD48⁺CD244⁺

For HSCs, CD150⁺CD48^- was sufficient instead of CD150⁺CD48^-CD244^- because CD48 is a ligand for CD244, and both would be positive only in the activated lineage-restricted progenitors. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. CD244 ( C luster of D ifferentiation 244 is a human Protein encoded by the Gene. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. CD244 ( C luster of D ifferentiation 244 is a human Protein encoded by the Gene. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. CD244 ( C luster of D ifferentiation 244 is a human Protein encoded by the Gene. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. CD244 ( C luster of D ifferentiation 244 is a human Protein encoded by the Gene. It seems that this code was more efficient than the more tedious earlier set of the large number of markers, and are also conserved across the mouse strains; however, recent work has shown that this method excludes a large number of HSCs and includes an equally large number of non-stem cells. ^{[8] [9]}. CD150⁺CD48^- gave stem cell purity comparable to Thy1^loSca-1⁺lin^-c-kit⁺ in mice. Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD48 ( C luster of D ifferentiation 48 is a human Protein encoded by the Gene. Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types ^[10]

Irving Weissman's group at Stanford University that was the first to isolate mouse hematopoietic stem cells in 1988, was also the first to work out the markers to distinguish the mouse long-term (LT-HSC) and short-term (ST-HSC) hematopoietic stem cells (self-renew-capable), and the Multipotent progenitors (MPP, low or no self-renew capability — the later the developmental stage of MPP, the lesser the self-renewal ability and the more of some of the markers like CD4 and CD135):

• LT-HSC : CD34^-, SCA-1⁺ , Thy1.1^+/lo, C-kit⁺, lin^-, CD135^-, Slamf1/CD150⁺
• ST-HSC : CD34⁺, SCA-1⁺ , Thy1.1^+/lo, C-kit⁺, lin^-, CD135^-, Slamf1/CD150⁺, Mac-1 (CD11b)^lo
• Early MPP : CD34⁺, SCA-1⁺ , Thy1.1^-, C-kit⁺, lin^-, CD135⁺, Slamf1/CD150^-, Mac-1 (CD11b)^lo, CD4^lo
• Late MPP : CD34⁺, SCA-1⁺ , Thy1.1^-, C-kit⁺, lin^-, CD135^high, Slamf1/CD150^-, Mac-1 (CD11b)^lo, CD4^lo

Nomenclature of hematopoietic colonies and lineages

Between 1948 and 1950, the Committee for Clarification of the Nomenclature of Cells and Diseases of the Blood and Blood-forming Organs issued reports on the nomenclature of blood cells. Irving L "Irv" Weissman MD is a Professor of Pathology and Developmental Biology at Stanford University where he is the Director of the Stanford Institute of Stem Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private Research university located in CD 135 is a Cytokine receptor expressed on the surface of Hematopoietic progenitor cells CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types CD 135 is a Cytokine receptor expressed on the surface of Hematopoietic progenitor cells Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types CD 135 is a Cytokine receptor expressed on the surface of Hematopoietic progenitor cells Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. Integrin alpha M (ITGAM is one protein subunit that forms the Heterodimeric Integrin alpha-M beta-2 (αMβ2 molecule also known as macrophage-1 CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types CD 135 is a Cytokine receptor expressed on the surface of Hematopoietic progenitor cells Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. Integrin alpha M (ITGAM is one protein subunit that forms the Heterodimeric Integrin alpha-M beta-2 (αMβ2 molecule also known as macrophage-1 CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, CD34 molecule is a Cluster of differentiation Molecule present on certain cells within the human body Discovery and Nomenclature Thy-1 was discovered in early 1960s during the search for heterologous antisera against mouse Leukemia cells CD117, also called KIT or C-kit receptor, is a Cytokine receptor expressed on the surface of Hematopoietic stem cells as well as other cell types CD 135 is a Cytokine receptor expressed on the surface of Hematopoietic progenitor cells Signaling lymphocytic activation molecule family member 1, also known as SLAMF1, is a human Gene. Integrin alpha M (ITGAM is one protein subunit that forms the Heterodimeric Integrin alpha-M beta-2 (αMβ2 molecule also known as macrophage-1 CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, ^[11][12] An overview of the terminology is shown below, from earliest to final stage of development:

• [root]blast
• pro[root]cyte
• [root]cyte
• meta[root]cyte
• mature cell name

The root for CFU-E is "rubri", for CFU-GM is "granulo" or "myelo" and "mono", for CFU-L is "lympho" and for CFU-Me is "megakaryo". According to this terminology, the stages of red blood cell formation would be: rubriblast, prorubricyte, rubricyte, metarubricyte, and erythrocyte. However, the following nomenclature seems to be, at present, the most prevalent:

Osteoclasts also arise from haemopoietic cells of the monocyte/neutrophil lineage, specifically CFU-GM. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. The term myeloid suggests an origin in the Bone marrow or Spinal cord, or a resemblance to the marrow or spinal cord Lymphopoiesis refers to the generation of Lymphocytes or Lymphoid Hematopoiesis. Erythropoiesis is the process by which Red blood cells (erythrocytes are produced Haematopoiesis (from Ancient Greek haima blood poiesis to make (or hematopoiesis in the United States sometimes also haemopoiesis or Lymphoblasts are immature cells which typically differentiate to form mature Lymphocytes Normally lymphoblasts are found in the bone marrow but in Acute lymphoblastic A proerythroblast (or rubriblast, or pronormoblast) is the earliest of four stages in development of the Normoblast. The myeloblast is a unipotent stem cell which will differentiate into one of the actors of the Granular series Monoblasts are normally found in bone marrow and do not appear in the normal peripheral blood A megakaryoblast is a precursor cell to a Promegakaryocyte, which in turn becomes a Megakaryocyte during Haematopoiesis. Found during Lymphocytopoiesis, a prolymphocyte is the immediate precursor of a Lymphocyte, derived from a Lymphoblast. An erythroblast is a type of red blood cell which still retains a Cell nucleus. A promyelocyte (or progranulocyte) is a Granulocyte precursor developing from the Myeloblast and developing into the Myelocyte. A promonocyte (or premonocyte) is a cell arising from a Monoblast and developing into a Monocyte. A promegakaryocyte is a precursor cell for a Megakaryocyte, arising from a Megakaryoblast. An erythroblast is a type of red blood cell which still retains a Cell nucleus. A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Reticulocytes are immature Red blood cells typically composing about 1% of the red cells in the human body A metamyelocyte is a cell undergoing Granulopoiesis, derived from a Myelocyte, and leading to a Band cell. A band cell (or band neutrophil) is a cell undergoing Granulopoiesis, derived from a Metamyelocyte, and leading to a mature Granulocyte. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Granulocytes are a category of White blood cells characterised by Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components 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 Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Thrombocytes are cells that play a key role in blood clotting Platelets, or Thrombocytes, are small cytoplasmic bodies derived from cells They circulate in the Blood of Mammals and are involved

Colony-forming units

There are various kinds of colony-forming units:

• Colony-forming unit lymphocyte (CFU-L)
• Colony-forming unit erythrocyte (CFU-E)
• Colony-forming unit granulo-monocyte (CFU-GM)
• Colony-forming unit megakaryocyte (CFU-Me)
• Colony-forming unit Basophil (CFU-B)
• Colony-forming unit Eosinophil (CFU-Eo)

The above CFUs are based on the lineage. In Microbiology, colony-forming unit ( CFU) is a measure of viable Bacterial or Fungal numbers A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Monocyte is a type of Leukocyte, part of the Human body 's Immune system. The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components Another CFU, the colony-forming unit–spleen (CFU–S) was the basis of an in vivo clonal colony formation, which depends on the ability of infused bone marrow cells to give rise to clones of maturing hematopoietic cells in the spleens of irradiated mice after 8 to 12 days. It was used extensively in early studies, but is now considered to measure more mature progenitor or Transit Amplifying Cells rather than stem cells.

References

1. ^ Muller-Sieburg CE, Cho RH, Thoman M, Adkins B, Sieburg HB, Deterministc regulation of hematopoietic stem cell self-renewal and differentiation. Blood. 2002; 100; 1302-9
2. ^ Muller-Sieburg CE, Cho RH, Karlson L, Huang JF, Sieburg HB. Myeloid-biased hematopoietic stem cells have extensive self-renewal capacity but generate diminished progeny with impaired IL-7 responsiveness. Blood. 2004; 103:4111-8.
3. ^ Sieburg HB, Cho RH, Dykstra B, Eaves, CJ, Muller-Sieburg, CE. The hematopoietic stem cell compartment consists of a limited number of discrete stem cell subsets. Blood. 2006; 107:2311-6. Epub 2005 Nov 15.
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Additional images

Hematopoiesis

See also

• Haematopoiesis

External links

• MeSH Hematopoietic+stem+cells
• hemocytoblast at eMedicine Dictionary