Peptide–major histocompatibility complex class I complex (Peptide–MHC I complex (pMHC I))

The peptide–MHC class I complex is a cell-surface protein assembly composed of a membrane-bound MHC I heavy chain, β2-microglobulin (β2m), and a short peptide (typically 8–10 amino acids) generated from endogenous cellular proteins by proteasomal degradation. Peptide loading occurs in the endoplasmic reticulum via the peptide-loading complex (PLC), including TAP, tapasin, ERp57, and calreticulin. Once loaded, the stable complex is displayed on the cell surface, where it can be recognized by CD8^+ cytotoxic T lymphocytes via their T cell receptors, leading to immune responses against infected or abnormal (e.g., cancerous) cells. The structural dynamics and affinity of peptide–MHC I recognition are critical for immune specificity and efficacy. This molecular complex is pivotal for adaptive immunity and deeply studied as a therapeutic target and biomarker in oncology, infectious disease, and immune disorders.

Other names

Peptide–MHC I complexpMHC IMHC class I:peptide complexpeptide-bound MHC class I

Recognition by T cell receptor (TCR) triggers T cell activation and cytotoxic response; Peptide-based drugs may block or mimic antigen presentation to stimulate or suppress immune response