title: The human lymphocyte function-associated (HLFA) antigen and a related macrophage differentiation antigen (HMac-1): functional effects of subunit-specific monoclonal antibodies.
abstract: The structural and functional relations between the alpha- and beta-subunits of the human lymphocyte function-associated antigen (HLFA) and the human Mac-1 antigen (HMac-1) have been analyzed with the use of five monoclonal antibodies that react with these proteins. The specificities of these antibodies were examined by immunoprecipitation of proteins from 125I-labeled cells and purified HLFA and HMac-1 antigens. Three antibodies reacted with the Mr 95,000 common beta-subunit of the proteins, and also co-precipitated the Mr 175,000 HLFA alpha-subunit, the Mr 165,000 HMac-1 alpha-subunit, and a third polypeptide alpha-subunit of Mr 150,000. The other antibodies were specific to noncross-reactive epitopes present on the alpha-subunits of HLFA or HMac-1. These specificities were confirmed in sequential immunoprecipitation studies. Peptide mapping showed that the beta-subunits of HLFA and HMac-1 were identical, whereas the two alpha-subunits differed considerably. The HLFA alpha-subunit-specific monoclonal antibody inhibited phytohemagglutinin stimulation, the mixed lymphocytes reaction, cytolytic T lymphocyte-mediated killing, and tetanus toxoid stimulation, but did not affect natural killer cell-mediated killing or complement receptor type 3 function. The HMac-1 alpha-subunit-specific monoclonal antibody inhibited complement receptor type 3 function but had no effect on T cell or natural killer cell functions. Three monoclonal antibodies to the beta-subunit inhibited all functions tested, including T cell, natural killer cell, and complement receptor type 3 activities. The results suggest that the functions of the HLFA and HMac-1 molecules may be determined by the alpha-subunit, and that the common beta-subunit also bears functionally important epitopes.
authors.forename: J E
authors.initials: JE
authors.lastname: Hildreth
authors.forename: J T
authors.initials: JT
authors.lastname: August
mesh_terms: D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000954:Antigens, Surface / Q000276:immunology*; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D003602:Cytotoxicity, Immunologic; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007525:Isoelectric Focusing; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000276:immunology; D011233:Precipitin Tests
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000939:Epitopes; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D010446:Peptide Fragments