Major histocompatibility complex class I molecule (MHC class I)

Major histocompatibility complex class I molecules are membrane-bound glycoproteins expressed on all nucleated cells. They present short peptides derived from intracellular proteins—including viral antigens and mutated self-proteins—to cytotoxic CD8+ T lymphocytes. This enables the immune system to detect infected or transformed cells for elimination. Structurally, each consists of an alpha chain encoded by highly polymorphic genes (HLA-A/B/C) non-covalently associated with beta2-microglobulin; together they form a peptide-binding groove that accommodates peptides typically eight-to-ten amino acids long[1][4]. Proper folding and surface expression require both peptide binding and association with beta2-microglobulin[6]. Defects in this pathway allow cancers and viruses to evade immune surveillance; conversely, excessive activity may underlie autoimmune pathology or transplant rejection responses[3].

Other names

Human leukocyte antigen class I (HLA-I)HLA-AHLA-BHLA-C (human gene products)MHC-IClass I major histocompatibility antigen

Enhancement or restoration of antigen processing/presentation increases CD8+ T cell-mediated killing. Loss/downregulation impairs immune detection and is associated with resistance to immunotherapy in cancer.