Major Histocompatibility Complex Molecule (MHC)

The major histocompatibility complex (MHC) is a set of cell surface proteins essential for the adaptive immune system. MHC molecules bind peptide fragments derived from pathogens or self-proteins and display them on the cell surface for recognition by T cells. In humans, the MHC is referred to as the human leukocyte antigen (HLA) system. The HLA gene cluster is located on chromosome 6p21.3. There are three main classes of genes: Class I, Class II, and Class III. Class I MHC molecules present endogenous peptides to CD8+ cytotoxic T cells, while Class II MHC molecules present exogenous peptides to CD4+ helper T cells. Class III encodes complement components and cytokines; not directly involved in peptide presentation. MHC genes are highly polymorphic, ensuring broad population-level protection against pathogens but also underlying tissue transplant rejection and influencing susceptibility or resistance to autoimmune diseases.

Other names

Human Leukocyte AntigenHLA

MHC molecules present peptide antigens to T cells, initiating adaptive immune responses. Drugs targeting MHC indirectly modulate these responses by affecting T cell activation or antigen presentation.