Peptide–major histocompatibility complex on infected cell (None; commonly abbreviated as "peptide–MHC complex" (no standardized short form))

The **peptide–major histocompatibility complex (peptide–MHC) on infected cells** is a molecular complex formed when fragments of intracellular (or, for class II, extracellular) proteins (“peptides”) are loaded onto major histocompatibility complex (MHC) molecules and displayed on the cell surface. For MHC class I, these complexes are present on nearly all nucleated cells and present peptides derived from endogenous proteins—critically, this includes peptides from viruses, intracellular bacteria, or cancer-related mutant proteins[1][2][4][7]. Cytotoxic T lymphocytes (CTLs), via their T-cell receptors (TCRs), scan peptide–MHC I complexes, triggering killing of infected or malignant cells if foreign or mutated peptides are recognized. MHC class II molecules, in contrast, are found mainly on specialized antigen-presenting cells (APCs) and present peptides from exogenous proteins to helper T cells, orchestrating broader immune responses[1][3][6]. The peptide–MHC complex is central to adaptive immunity, dictating the specificity and breadth of T cell–mediated recognition and is a critical therapeutic target in immuno-oncology, infection, and autoimmunity[5][7].

Other names

peptide–MHC complexMHC–peptide complexantigen–MHC complexpeptide-bound MHCpeptide–MHC I complex (for class I)peptide–MHC II complex (for class II)

Drugs or biologics targeting this complex typically work by: - Enhancing T-cell recognition of infected or malignant cells (e.g., by immune checkpoint inhibition) - Blocking or presenting specific peptides to modulate immune response - Therapeutic vaccines designed to elicit T-cell responses to novel peptide–MHC complexes