MHC (major histocompatibility complex) Class II molecules are found only on a few specialized cell types, including macrophages, dendritic cells and B cells, all of which are professional antigen-presenting cells (APCs). The major histocompatibility complex ( MHC) is a large genomic region or Gene family found in most Vertebrates It is the most gene-dense region Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Dendritic cells (DCs are Immune cells and form part of the Mammalian Immune system. 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 See also Antigen presentation An antigen-presenting cell ( APC) or accessory cell is a cell that displays foreign Antigen complexed
The peptides presented by class II molecules are derived from extracellular proteins (not cytosolic as in class I); hence, the MHC class II-dependent pathway of antigen presentation is called the endocytic or exogenous pathway. There are two primary classes of Major histocompatibility complex (MHC molecules class I and MHC class II.
Loading of class II molecules must still occur inside the cell; extracellular proteins are endocytosed, digested in lysosomes, and bound by the class II MHC molecule prior to the molecule's migration to the plasma membrane. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases.
Contents |
Structure
Like MHC class I molecules, class II molecules are also heterodimers, but in this case consist of two homologous peptides, an α and β chain, both of which are encoded in the MHC. A dimer is a Chemical or Biological entity consisting of two subunits called Monomers which are held together by either Intramolecular forces
Because the antigen-binding groove of MHC class II molecules is open at both ends while the corresponding groove on class I molecules is closed at each end, the antigens presented by MHC class II molecules are longer, generally between 15 and 24 amino acid residues long. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this
Reaction to bacteria
Because class II MHC is loaded with extracellular proteins, it is mainly concerned with presentation of extracellular pathogens (for example, bacteria that might be infecting a wound or the blood). Class II molecules interact exclusively with CD4+ ("helper") T cells (THs). CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, The helper T cells then help to trigger an appropriate immune response which may include localized inflammation and swelling due to recruitment of phagocytes or may lead to a full-force antibody immune response due to activation of B cells. 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 Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens
Synthesis
During synthesis, MHC class II is the result of dimerization of α and β chains, with the assistance of an invariant chain. [1]
Genes
| Alpha | Beta | |
| HLA-DM | HLA-DMA | HLA-DMB |
| HLA-DO | HLA-DOA | HLA-DOB |
| HLA-DP | HLA-DPA1 | HLA-DPB1 |
| HLA-DQ | HLA-DQA1, HLA-DQA2 | HLA-DQB1, HLA-DQB2, HLA-DQB3 |
| HLA-DR | HLA-DRA | HLA-DRB1, HLA-DRB2, HLA-DRB3, HLA-DRB4, HLA-DRB5 |
References
- ^ School of Crystallography The Invariant chain
External links
HLA-DM is an Intracellular protein involved in peptide presentation by MHC class II. Major histocompatibility complex class II DM alpha, also known as HLA-DMA, is a human Gene. Major histocompatibility complex class II DM beta, also known as HLA-DMB, is a human Gene. HLA-DO is a dimeric Protein composed of α- and β -subunits which assists in the down-regulation of HLA-DM. Major histocompatibility complex class II DO alpha, also known as HLA-DOA, is a human Gene. Major histocompatibility complex class II DO beta, also known as HLA-DOB, is a human Gene. HLA-DP is a protein/peptide-antigen receptor and Graft-versus-host disease antigen that is composed of 2 subunits DPα and DPβ Major histocompatibility complex class II DP beta 1, also known as HLA-DPB1, is a human Gene. HLA-DQ (DQ is a cell surface receptor type Protein found on Antigen presenting cells DQ is an αβ Heterodimer of the MHC Class II type Major histocompatibility complex class II DQ alpha 1, also known as HLA-DQA1, is a human Gene and also denotes the genetic locus which contains this gene Major histocompatibility complex class II DQ alpha 2, also known as HLA-DQA2, is a human Gene. Major histocompatibility complex class II DQ beta 1, also known as HLA-DQB1, is a human Gene and also denotes the genetic locus which contains this gene Major histocompatibility complex class II DQ beta 2, also known as HLA-DQB2, is a human Gene. HLA-DR is a Major histocompatibility complex, MHC class II, Cell surface receptor encoded by the Human leukocyte antigen complex on chromosome HLA-DR is a Major histocompatibility complex, MHC class II, Cell surface receptor encoded by the Human leukocyte antigen complex on chromosome Major histocompatibility complex class II DR beta 1, also known as HLA-DRB1, is a human Gene. Major histocompatibility complex class II DR beta 3, also known as HLA-DRB3, is a human Gene. Major histocompatibility complex class II DR beta 4, also known as HLA-DRB4, is a human Gene. Major histocompatibility complex class II DR beta 5, also known as HLA-DRB5, is a human Gene. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and booksDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic