ABSTRACT
Antigen-specifi c receptors on T cells are similar, but not identical to those on B cells. Interaction of the cell receptor (T-cell receptor [TCR]) with the antigen in the proper context leads to stimulation of the specifi c T cell to become activated and to proliferate, leading to clonal selection. The TCR complex is made of membrane proteins including the TCR, which recognizes the antigen, and a set of proteins called the CD3 complex, which leads to signal transduction and activation of T cells. Recognition and binding of the antigen to its specifi c receptor initiates the activation process, that is, downstream signaling pathways such as protein phosphorylation, the release of inositol phosphates, and the elevation of intracellular calcium levels. Because the adaptive immune system recognizes billions of unique antigens using highly variable TCRs, generation and maintenance of an effective repertoire of TCRs for diverse antigen recognition is essential to the immune system. Detection and monitoring of the TCR repertoire is important in diagnosing a T-cell malignancy, autoimmune phenomena, or response to immunotherapy.
