Antigenic peptide–MHC class I complex (pMHC-I)

An **antigenic peptide–MHC class I complex** (pMHC-I) is a membrane-bound molecular complex consisting of a short antigenic peptide, typically 8–10 amino acids long, presented in a groove formed by the MHC class I molecule. The MHC class I molecule is a heterodimer comprising a polymorphic heavy chain and an invariant β2-microglobulin subunit. Peptide assembly in the endoplasmic reticulum is facilitated by multiple chaperones (tapasin, calreticulin, ERp57, TAPBPR), which ensure only high-affinity peptides are loaded for stable cell surface presentation. On the surface of tumor cells, pMHC-I complexes permit immune surveillance by cytotoxic CD8+ T lymphocytes, which recognize specific antigens via the T cell receptor, leading to targeted destruction of infected or malignant cells. Recognition and presentation of these complexes are central to adaptive immunity, cancer immunotherapies, and immune evasion mechanisms in tumors and viruses[1][2][3][4][5][6][7].

Other names

Peptide–MHC class I complexpMHC-IPeptide–HLA class I complex (in humans, HLA is the MHC gene family)Antigen-presenting MHC class I complexHLA–peptide complex (especially in human references)

Immune activation by antigen presentation: Drug or therapy induces/recognizes pMHC-I on tumor cells, leading to T cell–mediated killing Targeted cytotoxicity: Engaged CD8+ T cells recognize peptide-MHC-I on tumor cells, inducing apoptosis Immune checkpoint release: Drugs release inhibitory brakes allowing T cells specific for pMHC-I to act