CD3ε is a 20 kD transmembrane protein, also known as CD3 or T3. It is a member of the Ig superfamily, mainly expressed on T cells and NK-T cells, and expressed at different levels on thymocytes during the process of T cell differentiation. CD3ε forms TCR complexes by binding to CD3δ, γ and δ chains as well as TCR α/β or γ/δ chains. CD3 plays a key role in TCR signal transduction, T cell activation and antigen recognition by binding to peptide /MHC antigen complexes.
