A monoclonal antibody (BMA-1) reactive with murine B cells as well as resident and elicited but not activated macrophages

Hybridoma technology has been employed to prepare a monoclonal antibody that recognizes a sub-population of mononuclear leukocytes. Enzyme-linked immune assay revealed a cell clone producing a monoclonal antibody reactive with elicited but not activated C57Bi/6 peritoneal macrophages. Detailed analyses using fluorescence flow cytometry demonstrated that this monoclonal antibody binds to B cells, B cell blasts, as well as to the resident and elicited macrophages, but not to activated macrophages, T cells, red blood cells, or syngeneic fibroblasts. This antigen has been designated BMA-1. Antigenic expression is greatest upon resident macrophages. A bimodal level of expression is found on elicited macrophages while activated macrophages possess low levels of expression. The unique cellular distribution of this antigen indicates that it is lost during macrophage differentiation to the activated state. Immunoprecipitation studies indicate that this antigen is composed of multiple subunits; the primary subunit possesses a molecular weight of 38,000. This new tool should be valuable in the analysis of heterogeneous macrophage populations and in defining molecular differentiation pathways.