The CD3 antibody recognizes the 17-19 kD ε-chain of CD3 within the CD3 antigen/T cell antigen receptor (TCR) complex. The CD3 antigen is expressed in the cell cytoplasm during the early stage of T cell development and is expressed on the cell membrane at the late stage. CD3 antigen is displayed on 60-80% of normal peripheral blood lymphocytes and 60-70% of thymocytes and plays an important role in signal transduction after antigen recognition by TCR. NK cells also express the CD3 antigen in the cytoplasm. Product Cat. No. 252265 is the FITC conjugate of Cat. No. 250588.