Abstract
New activated macrophage-specific antigen (AcM.1) detected by a monoclonal antibody was described. The AcM.1 antigen was only detectable on activated [rat and mouse] macrophages induced by pyran and Corynebacterium parvum [Propionibacterium acnes] but not on resident or thioglycollate medium (TGC), proteose-peptone and mineral oil-elicited macrophages, and not on blood monocytes and neutrophils. Activated macrophages induced by pyran and C. parvum, as expected, exhibited tumor cytotoxicity, whereas TGC-elicited macrophages did not show any cytotoxicity. Pretreatment of pyran-activated peritoneal exudate cells with AcM.1 antibody plus complement abolished .apprx. 80% cytotoxicity. This AcM.1 antigen detected by a monoclonal antibody is the 1st unique marker of activated tumoricidal macrophages and should provide a useful probe for investigating the mechanisms of activation or differentiation of macrophages.