CD3 [PC3/188A]

CD3 is a protein complex and T cell co-receptor that is involved in activating both the cytotoxic T cell and T helper cells. It is composed of four distinct chains CD3γ, CD3δ, and two CD3ε chains in mammals. These chains associate with the T-cell receptor (TCR) and the CD3-zeta (ζ-chain) to generate activation signal in T lymphocytes. The TCR, CD3-zeta, and the other CD3 molecules together constitute the TCR complex. CD3 is initially expressed in the cytoplasm of pro-thymocytes, the stem cells from which T-cells arise in the thymus. The pro-thymocytes differentiate into common thymocytes, and then into medullary thymocytes, and it is at this latter stage that CD3 antigen begins to migrate to the cell membrane. The antigen is highly specific marker for T cells, remains present in almost all T-cell lymphomas and leukaemias, and can therefore be used to distinguish them from superficially similar B-cell and myeloid neoplasms. This monoclonal antibody recognizes the epsilon-chain of CD3. CD3 epsilon subunit is the most exposed of the native CD3 structures which are immunogenic and that cross-linking of the CD3 epsilon chain by the monoclonal antibody mediates the subsequent T cell activation via the T cell receptor complex.