Peptide–major histocompatibility complex complex and T-cell receptor (TCR–pMHC complex)

The **peptide–major histocompatibility complex (MHC) complex and T-cell receptor (TCR)** form the central recognition unit of cellular adaptive immunity. The TCR is a membrane-bound heterodimer (usually αβ chains) present on T cells that specifically recognizes short peptides (typically 8–15 amino acids) presented by MHC molecules on the surface of other cells. The TCR does not bind free peptides; instead, it recognizes a composite surface formed by the peptide and MHC, a structure termed the "pMHC" complex. TCR binding to pMHC is the pivotal event initiating T-cell activation, leading to downstream immune signaling that can result in cell-mediated cytotoxicity, cytokine release, or modulation of immune responses[2][3][4][6]. Structural features of the complex—such as the conserved diagonal docking of the TCR over the pMHC, with germline-encoded regions of the TCR contacting MHC and hypervariable regions contacting the peptide—ensure both diversity and specificity in antigen recognition[1][3][4][5][6][7]. TCR–pMHC interactions are central to disease pathogenesis and to immunotherapeutics, especially in cancer (where tumor-associated pMHCs become targets for TCR-based therapies), autoimmunity (where self pMHCs are mistakenly recognized), and infectious diseases[6][7]. While there are currently no approved small molecules or mAbs that disrupt TCR–pMHC binding directly, various therapies modulate this axis indirectly or engineer cells to harness the specificity of the TCR–pMHC interaction[6].

Other names

TCR–peptide–MHC complexT-cell receptor–peptide–MHC complexTCR–pMHCT-cell receptor–MHC complex

Inhibition or modulation of T-cell activation (by blocking costimulatory signals or TCR signal transduction); Redirected antigen specificity (by engineered TCR or bispecific T cell engagers); Immune checkpoint blockade (modulates downstream signaling, not TCR-pMHC directly)