PeptidMHCIKomplex

PeptidMHCIKomplex refers to the molecular complex formed by an MHC class I molecule bound to a short peptide. In vertebrates, MHC class I molecules present endogenous peptides on the cell surface to CD8+ T cells, enabling immune surveillance for infected or malignant cells. MHC class I molecules are heterotrimers composed of a polymorphic heavy chain (α chain, with α1, α2, α3 domains) associated with β2-microglobulin. The antigen-binding groove is formed by α1 and α2 and binds short peptides typically 8-11 amino acids long. The peptide's side chains occupy specific pockets in the groove, and many MHC alleles show strong preferences for certain residues at anchor positions, shaping the peptide–MHC interface recognized by the T cell receptor (TCR) in the context of CD8.

Biogenesis and loading: In the endoplasmic reticulum, the heavy chain associates with β2-microglobulin and is stabilized by chaperones such as calnexin. The complex then binds calreticulin and the peptide-loading complex, including tapasin and ERp57, which optimizes peptide selection. TAP transporters supply cytosolic peptides; high-affinity peptides stabilize the complex, which is transported to the cell surface as the PeptidMHCIKomplex.

Function: The surface PeptidMHCIKomplex is surveyed by CD8+ T cells. Recognition of foreign or altered peptides triggers T cell activation and cytotoxic responses, contributing to clearance of infections and tumors.

Clinical relevance: PeptidMHCIKomplex composition influences vaccine efficacy, cancer immunotherapy, transplantation compatibility, and autoimmune risk. Research often focuses on identifying immunogenic peptides and engineering MHC class I pathways to enhance presentation.