What is the structure of T cell receptor?

A T cell receptor (TCR) is made up of two polypeptide chains, which form one antigen binding region.

The large majority (about 95%) of T cell receptors are composed of an alpha and a beta chain. The remaining 5% of TCRs are composed of a gamma and a delta chain. The two chains are linked by a disulfide bond, which helps maintain the structure of the T cell receptor. 

The lower portion of the polypeptide chains forms the constant region of the TCRs, while the top portion forms the variable region. Complementary determining regions (CDRs), which are present within the variable region, are responsible for providing the specificity in antigen binding.