Major Histocompatibility Complex (MHC)
Vertebrate organisms posses a cluster of genes named the Major Histocompatibility Complex (MHC). The MHC is referred to as the HLA complex in humans and as the H-2 complex in mice.
The MHC-encoded protein products play a role in the development of both humoral (antibody-mediated) and cell-mediated immune responses. MHC class I molecules* are expressed in nearly all nucleated cells. They are involved in the presentation of endogenous peptide antigens to CD8+ cytotoxic T cells. Examples of endogenous peptide antigens include normal cellular proteins, tumor proteins, and viral or bacterial antigens produced within infected cells.
*) Immunity (Class I)
T lymphocytes play a critical role in the immune system. The measurement of total T cells and T-cell subsets is carried out by detecting various cell-surface molecules.
Each T cell expresses a specific T-cell receptor (TCR) on its surface. The TCR recognizes a given MHC molecule to which a peptide is bound. For MHC class I, the peptides are derived from the intracellular protein turnover of expressed proteins. The typical target markers are thus T cells recognizing peptides derived from tumor antigens, viral proteins or normal proteins bound to an MHC class I molecule.
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