Characterization of a novel leucocyte activation antigen recognized by the antibody CMRF-37

We describe a novel activation antigen recognized by the monoclonal antibody CMRF-37, which is absent or only weakly expressed on resting cells but is rapidly induced on T cells, B cells and monocytes following stimulation. Its kinetics of expression (12-24 h after the addition of the inductive signal) indicate that it is an early activation antigen. The cellular distribution and expression kinetics of the CMRF-37 antigen differ from other known activation antigens and as such should be a useful marker of human leucocyte activation.