{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"The T cell receptor or TCR is a protein found on the surface of T lymphocytes that is responsible for recognizing antigens bound to major histocompatibility complex (MHC) molecules. The TCR is a heterodimer composed of two different protein chains. In 95% of T cells, TCR consists of an alpha (α) and beta (β) chain, whereas in 5% of T cells, TCR consists of gamma and delta (γ/δ) chains. TCR Alpha is a member of the immunoglobin superfamily and a component of the CD3/TCR complex (along with TCR Beta). TCR Alpha is expressed by thymocytes and a majority of peripheral (α-β TCR-bearing) T-cells. TCR recognition of self-peptides has been linked to autoimmune disease. TCR recognition of mutated self-peptides have been associated with T-cell response to tumors."}]}]}