Peptide-major histocompatibility complex on antigen-presenting cell and T-cell receptor (Peptide-MHC complex and TCR)

The **peptide-major histocompatibility complex (MHC) on antigen-presenting cells and T-cell receptor (TCR)** on T lymphocytes form a fundamental molecular recognition system at the heart of the adaptive immune response[1][5][6]. Peptide antigens generated from intracellular or extracellular pathogens, mutated self-proteins (in cancer), or self molecules (in autoimmunity) are presented on cell surfaces by MHC molecules (Class I or II, depending on APC type)[2][3][6]. TCRs, primarily composed of α and β chains, interact specifically with both the peptide and the MHC molecule through highly variable regions called complementarity-determining regions (CDRs)[1][3][5]. This complex determines antigen specificity, initiates T-cell signaling when a cognate antigen is encountered, and drives diverse downstream effects including cell-mediated cytotoxicity, cytokine production, and immune memory formation[5][6]. The peptide-MHC:TCR interface is now a therapeutic target for engineered TCRs, peptide vaccines, and immune modulators, but it presents unique challenges related to specificity, off-target reactions, and functional diversity[5]. The structural basis of this interaction is crucial for predicting and engineering T-cell responses, making it highly relevant to immunotherapy, autoimmunity, and transplant biology[4][5][6].

Other names

peptide-MHC complexpMHC:TCR complexpMHC-TCRTCR-pMHCT-cell receptor:peptide-MHC complexTCR-pMHC interface

Modulation of T-cell activity by disrupting or enhancing TCR-pMHC recognition[5]; Blockade of co-inhibitory signals to unleash TCR-mediated cytotoxicity; Engineering high-affinity TCRs to target tumor-associated pMHC antigens; Presentation of altered peptides by MHC to modify TCR responses