"The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system."
These are a group of genes that code for the molecules present on the surface of cells and play a critical role in immunological reactions.
Antigen presentation: The process by which MHC molecules display foreign antigens to T cells.
MHC class I: A class of MHC molecules expressed on all nucleated cells that present endogenous antigens to cytotoxic T cells.
MHC class II: A class of MHC molecules expressed on antigen-presenting cells that present exogenous antigens to helper T cells.
Immunodominance: The phenomenon in which some epitopes on an antigen elicit a stronger immune response than others.
Allelic diversity: The large number of different MHC alleles that exist in a population, leading to individual variation in MHC molecule expression and antigen presentation.
T cell receptor (TCR): The protein on the surface of T cells that recognizes antigen-MHC complexes.
Co-stimulation: The requirement for additional signals (e.g. CD28-B7 interaction) in addition to TCR signaling for T cell activation.
Immunological memory: The ability of the immune system to remember previously encountered antigens and mount a more rapid and effective response upon re-exposure.
Autoimmune diseases: Disorders in which the immune system attacks self-antigens presented on MHC molecules.
Immune evasion: Strategies employed by pathogens to evade detection and destruction by the immune system, including MHC downregulation and antigenic variation.
MHC Class I: Present on almost all nucleated cells, MHC class I molecules present endogenously synthesized peptides to CD8+ T cells. They consist of a single chain composed of three domains (α1, α2, and α3) complexed with β2 microglobulin.
MHC Class II: Present on specialized antigen-presenting cells such as dendritic cells, macrophages, and B-cells. MHC class II molecules present exogenously derived peptides to CD4+ T cells. They are composed of two chains, α and β each with two domains.
MHC Class III: This is a small region where most of the genes coding for cytokines are located. Some of the cytokines genes on MHC III include tumor necrosis factor alpha (TNFα), complement components and heat shock proteins.
Non-classical MHC: These MHC molecules are also known as non-classical because they do not fit into the Class I or Class II category due to their unique structure and diverse roles in the immune system. Examples of Non-classical MHC in humans include MICA and MICB and HLA-G.
"MHC molecules mediate the interactions of leukocytes, also called white blood cells (WBCs), with other leukocytes or with body cells."
"The MHC determines donor compatibility for organ transplant."
"The presented self-antigens prevent an organism's immune system from targeting its own cells."
"The presentation of pathogen-derived proteins results in the elimination of the infected cell by the immune system."
"Diversity of an individual's self-antigen presentation, mediated by MHC self-antigens, is attained in at least three ways."
"An organism's MHC repertoire is polygenic (via multiple, interacting genes)."
"MHC expression is codominant (from both sets of inherited alleles)."
"MHC gene variants are highly polymorphic (diversely varying from organism to organism within a species)."
"Sexual selection has been observed in male mice choosing to mate with females with different MHCs."
"Also, at least for MHC I presentation, there has been evidence of antigenic peptide splicing."
"Later studies revealed that tissue rejection due to incompatibility is only a facet of the full function of MHC molecules."
"These cell surface proteins are called MHC molecules."
"MHC molecules... code for cell surface proteins essential for the adaptive immune system... binding an antigen derived from self-proteins or from pathogens, and bringing the antigen presentation to the cell surface for recognition by the appropriate T-cells."
"The MHC determines... one's susceptibility to autoimmune diseases."
"An organism's MHC repertoire... is diversely varying from organism to organism within a species."
"The presented self-antigens prevent an organism's immune system from targeting its own cells."
"MHC molecules mediate the interactions of leukocytes, also called white blood cells (WBCs), with other leukocytes or with body cells."
"MHC expression is codominant (from both sets of inherited alleles)."
"At least for MHC I presentation, there has been evidence of antigenic peptide splicing, which can combine peptides from different proteins, vastly increasing antigen diversity."