CD3e monoclonal antibody

The T cell antigen receptor (TCR) recognizes foreign antigens and translates such recognition events into intracellular signals that elicit a change in the cell from a dormant to an activated state. Much of this signaling process can be attributed to a multisubunit complex of proteins that associates directly with the TCR. This complex has been designated CD3 (cluster of differentiation 3) . It is composed of five invariant polypeptide chains that associate to form three dimers: a heterodimer of g and e chains (CD3-g and CD3-e), a heterodimer of d and e chains (CD3-d and CD3-e) and a homodimer of two z chains (CD3-z) or a heterodimer of z and h chains (CD3-z and CD3-h) . CD3-z and CD3-h are encoded by the same gene, but differ in their carboxyl-terminal ends due to an alternative splicing event. CD3-g, CD3-e and CD3-d each contain a single copy of a conserved immunoreceptor tyrosine-based activation motif (ITAM) . In contrast, CD3-z contains three consecutive copies of the same motif. Phosphorylated ITAMs act as docking sites for protein kinases such as ZAP-70 and Syk and are also capable of regulating their kinase activity. The crystal structure of the ZAP-70 SH2 domains bound to CD3-z ITAMs has been solved.