Description | The T cell receptor (TCR) is the antigen receptor expressed on CD4- positive and CD8-positive T lymphocytes that recognizes complexes of peptides bound to self-MHC molecules on the surface of antigen presenting cells. Structurally, TCR is composed of a heterodimer of two disulfide-linked transmembrane polypeptide chains designated alpha and beta, each containing one terminal immunoglobulin (Ig)-like variable domain, one Ig-like constant domain, a hydrophobic transmembrane region and a short cytoplasmic region. A less common type of TCR, composed of gamma and delta chains, is found on a small subset of T cells and recognizes different forms of antigens. Each T cell expresses a unique TCR that is generated by randomly assorting genes. This ensures that T cells can respond (at the population level) to almost any infection |