The
T cell receptor or
TCR is a molecule found on the surface of
T lymphocytes (or T cells) that is responsible for recognizing fragments of
antigen as peptides bound to
major histocompatibility complex (MHC) molecules. The binding between TCR and antigen peptides is of relatively low affinity and is
degenerate: that is, many TCRs recognize the same antigen peptide and many antigen peptides are recognized by the same TCR.