Major histocompatibility complex molecule on antigen-presenting cell (MHC molecule)

Major histocompatibility complex molecules (also called human leukocyte antigens in humans) are highly polymorphic cell surface glycoproteins encoded by the MHC genetic region, which function to present peptide antigens to T lymphocytes, thus enabling the adaptive immune system to recognize pathogens, virally infected cells, and cancer cells[3][5][6]. There are two main classes: MHC class I molecules, expressed on all nucleated cells, present endogenously-derived peptides (such as viral antigens) to CD8+ cytotoxic T cells; MHC class II molecules, expressed primarily on professional antigen-presenting cells (dendritic cells, macrophages, B cells), present exogenously-derived peptides to CD4+ helper T cells[1][2][3][6][8]. MHC molecule binding grooves are highly variable, giving rise to an extraordinary diversity of peptide presentation and individual-specific immune responses[5][6][7]. The alleles of MHC class I (HLA-A, -B, -C) and class II (HLA-DR, -DP, -DQ) genes are clinically important for transplantation (where mismatches cause graft rejection), infection susceptibility, autoimmunity, and cancer immunotherapy[3][5][6]. Clarification and correction: "MHC molecules on antigen-presenting cells" refers mostly to MHC class II molecules (HLA-DR, -DQ, -DP) but also includes MHC class I molecules, especially for cross-presentation by dendritic cells[1][2][3][8]. For structured data, use precise entries: "Major histocompatibility complex class II molecule (HLA-DR, -DP, -DQ)" is the most specific relevant canonical form for the original query on APCs. The entry as written is overbroad ("MHC molecules" includes class I and II, on all cells and APCs); for drug targeting, most therapies affect T cell activation but not MHC molecules directly.

Other names

Human leukocyte antigen (HLA)MHC proteinMHC glycoprotein

Inhibition or modulation of T cell activation (by costimulatory blockade or immune suppression) or indirect interference with antigen presentation. Drugs listed act indirectly by modulating immune cell responses or costimulatory pathways, not by directly binding MHC molecules.