Characterization of a monoclonal antibody (4F2) that binds to human monocytes and to a subset of activated lymphocytes.

Abstract

This study characterizes a monoclonal antibody (4F2) and partially characterizes the cell-surface antigen and the peripheral blood (PB) mononuclear cells that it defines. The 4F2 antigen was present in varying amounts on every tissue culture cell line tested. Immunoprecipitation of an HSB-2 T cell extract with 4F2 under non reducing conditions yielded a specific band of a m.w. equal to 120,000. In the presence of 2-mercaptoethanol, immunoprecipitation of an HSB-2 extract with 4F2 yielded 2 specific bands, 1 of m.w. 40,000 and 1 of m.w. 80,000. 4F2 did not share reactivity with human HLA or la-like cell-surface antigens in that anti-HLA monoclonal anti-sera (3F10, W632) and anti-p23,30 heteroantisera did not block the binding of 4F2 to HSB-2 T cells. In addition, immunoprecipitation of HSB-2 T cell extracts with monoclonal anti-HLA (W6/32) did not remove the 4F2 antigen. By using directly fluoresceinated 4F2 antibody, analysis of separated PB mononuclear cell subsets with flow microfluorometry showed that among PB cells PB monocytes differentially bound the 4F2 antibody. However, upon activation with mitogens or alloantigens (e.g., Con A or allogeneic cells), a subset of T cells (70%) expressed the 4F2 antigen as well. The 4F2 antibody was not myogenic for PB mononuclear cells and did not block T cell blast transformation to allogeneic cells. However, 4F2 antibody did inhibit mitogen-induced tritiated thymidine incorporation of PB mononuclear cells by 50%. Moreover, 4F2 antibody did not block natural killer cell activity, antibody-dependent cellular cytotoxicity, or killing of allogeneic lymphocytes by alloantigen-sensitized T cells. Thus, the 4F2 antigen is a non-HLA, non-la cell surface marker present on human monocytes and on a subset of activated lymphocytes. The 4F2 antibody should be an important reagent in the study of monocyte physiology and the sequence of events that occurs during the activation of normal human lymphocytes.