Major histocompatibility complex molecule and T-cell receptor (as two distinct but functionally paired immune molecules) (MHC (major histocompatibility complex), TCR (T-cell receptor))

The **major histocompatibility complex (MHC) molecule** is a highly polymorphic glycoprotein that presents peptide antigens on the cell surface, enabling the immune system—specifically T cells—to recognize infected or aberrant cells. The **T-cell receptor (TCR)** is an antigen-specific receptor on the surface of T lymphocytes that recognizes these peptide-MHC complexes and, upon binding, initiates signaling that can activate, regulate, or kill target cells[1][2][3][4]. MHC and TCR work cooperatively: MHC molecules present peptides, while the TCR scans these complexes for foreign or abnormal epitopes, a partnership critical for adaptive immunity, self-tolerance, and protection against infectious and malignant diseases. Polymorphism of MHC genes restricts T cell responses to specific peptide/MHC combinations (“MHC restriction”), contributing to immune diversity, disease susceptibility, and challenges in transplantation[3][4].

Other names

MHCHuman leukocyte antigen (HLA, in humans)TCRCD3–TCR complex

Drugs may inhibit TCR signaling pathways to reduce T cell activation in transplantation or autoimmunity (e.g., calcineurin inhibitors suppress TCR-mediated transcriptional signals) Immunotherapies in oncology may exploit MHC/TCR interactions (e.g., checkpoint inhibitors, engineered TCR therapies)