CD3 epsilon: Proteins and Enzymes

The T cell receptor (TCR)/CD3 complex consists of two variable antigen-recognition receptor chains (TCR-alpha/TCR-beta or TCR-gamma/TCR-delta) that are non-covalently linked to at least four different invariant chains: CD3 gamma, CD3 delta, CD3 epsilon, and the CD3 zeta chain that exists as either a homodimer or as a heterodimer with its splice-variant the CD3 eta chain. The CD3 complex functions to transduce intracellular signals during TCR antigen recognition. CD3 is expressed early in thymocyte development, and on a subset of NK cells. CD3 epsilon is one of at least three invariant proteins that associate with the variable antigen recognition chains of the T cell receptor and function in signal transduction.