Definition of a common leukocyte cell-surface antigen (Lp95-150) associated with diverse cell-mediated immune functions.

We have described a monoclonal antibody, designated 60.3, which reacts with a cell surface antigen expressed by most peripheral blood and bone marrow leukocytes. Immunoprecipitation showed at least three major components with relative m.w. of 95,000, 130,000, and 150,000 under reducing conditions. Antibody 60.3 inhibited several cell-mediated immune functions. The lytic activity of both cytotoxic T cells and natural killer cells was blocked in the presence of the antibody. The proliferative responses of T cells stimulated by soluble antigens, mitogens, or allogeneic cells were inhibited when antibody 60.3 was added at the initiation of culture, but not when added after 48 hr. Antibody 60.3 also blocked the migration of neutrophilic granulocytes. The antigen identified by antibody 60.3 thus appears to be involved in a membrane-dependent cell activation pathway that is common to diverse functional systems and is shared by both lymphoid and myeloid cells.