[Detection of an early activation-dependent cell surface antigen on human T-lymphocytes]

The binding properties of a monoclonal antibody to an early activation marker of human lymphocytes are described. The monoclonal antibody BL-Ac/p26 binds to an antigen which is expressed on activated lymphocytes. This antigen is not detectable on resting lymphocytes or other blood cells. The surface radioiodinated antigen of activated T cells isolated by the monoclonal antibody BL-Ac/p26 is separated by SDS-PAGE in a major 26k Da component and a minor band (32 kDa) under reducing conditions. These polypeptide chains form disulphide linked dimers on the cell surface (Mr 55-77 kDa). This 26 kDa antigen is a very early activation marker of T lymphocytes. Human T lymphocytes stimulated by mitogens (PHA, ConA or PWM), anti-TCR/CD3 monoclonal antibodies or allogeneic leucocytes express this 26 kDa antigen after 2-4 hours.