The Final Touches Make Perfect the Peptide-MHC Class I Repertoire

SummaryMajor histocompatibility complex (MHC) class I molecules present short, perfectly cleaved peptides on the cell surface for immune surveillance by CD8+ T cells. The pathway for generating these peptides begins in the cytoplasm, and the peptide-MHC I (pMHC I) repertoire is finalized in the endoplasmic reticulum. Recent studies show that the peptides for MHC I are customized by the ER aminopeptidase associated with antigen processing and by dynamic interactions within the MHC peptide-loading complex. Failure to customize the pMHC I repertoire has profound immunological consequences.