MHC I

MHC I presents intracellular peptide antigens on nucleated cells for immune surveillance by CD8+ T cells[1]. Mechanistically, cytosolic proteins undergo proteasomal processing, peptide transport into the endoplasmic reticulum, loading onto MHC I, and surface display as peptide-MHC I complexes[2]. In viral infection and cancer models, altered MHC I antigen presentation supports immune evasion and affects tumor immunogenicity and immunotherapy response[3][4]. Compared with MHC II, which mainly presents exogenous antigens to CD4+ T cells, MHC I complexes are recognized by cytotoxic CD8+ T cells[5]. Among classical human MHC I isoforms, HLA-A, HLA-B, and HLA-C share overlapping functions, but each allomorph binds a distinct peptide repertoire determined by its peptide-binding groove[4]. For experimental applications, P2X7 receptor activation decreases plasma-membrane MHC I in antigen-presenting cells, while P2X7 antagonism or genetic ablation restores impaired peptide presentation[6].- MHC I links intracellular antigen processing to CD8+ T-cell immune surveillance.- HLA-A, HLA-B, and HLA-C differ mainly by peptide-binding repertoire.