Major histocompatibility complex molecule (peptide-bound form) (MHC (when peptide-bound, often pMHC))

Major histocompatibility complex molecules, when bound to peptide antigens (peptide-MHC complexes), are crucial cell-surface receptors involved in the adaptive immune response; they present processed peptide fragments to T cell receptors, thereby enabling the immune system to distinguish self from non-self and to initiate targeted immune responses against pathogens, tumors, or allogeneic cells[1][2][3][4][5]. In humans, these molecules are referred to as HLA (human leukocyte antigen) classes I and II, and are characterized by extraordinary genetic polymorphism, which allows a broad display of peptides[4][5]. Peptide-MHC class I complexes present endogenous peptides to CD8+ cytotoxic T lymphocytes, whereas peptide-MHC class II complexes present exogenous peptides to CD4+ helper T cells[1][4][5]. Polymorphisms in these molecules strongly influence disease susceptibility, resistance, and outcomes, notably in infection, autoimmunity, and transplantation[3][4][5]. As central elements in immune modulation and patient stratification, peptide-MHC complexes are targets for vaccines, immunotherapies, and diagnostics, and their genetic diversity complicates both therapeutic development and clinical implementation[3][4][5].

Other names

peptide-MHC complexpMHCMHC-peptide complexHLA-peptide complex (for humans)peptide-bound MHC class Ipeptide-bound MHC class II

Modulation of antigen presentation to T cells; Indirect mechanisms via enhancement or inhibition of T cell recognition