MUM-4, A MONOCLONAL-ANTIBODY REACTING WITH RESIDENT PERITONEAL MOUSE MACROPHAGES

A new rat monoclonal antibody, MUM-4, which recognizes a murine antigen/epitope that is absent on monocytes, strongly expressed on resident peritoneal macrophages and almost completely absent from peritoneal macrophages 4 days after an intraperitoneal injection of thioglycollate or heat-killed Propionibacterium acnes organisms, is described. Immunocytochemistry and flow cytometry have been used to characterize the specificity of the antibody. MUM-4 did not react with blood granulocytes, peritoneal exudate granulocytes, lymphocytes from blood or peritoneum, isolated spleen dendritic cells, or veiled cells from the thoracic duct of mesenteric lymphadenectomized mice. The MUM-4 antibody reacted with resident peritoneal macrophages from all the mouse strains studied. MUM-4 appears to represent a new specificity. The MUM-4 antibody is of the rat IgG2c isotype and exhibits complement-mediated cytotoxicity with rabbit complement. The staining achieved with MUM-4 by FACS or immunocytochemical methods is intense on most resident peritoneal macrophages and the antibody should be a valuable addition to the panel of monoclonal antibodies available for studies on mouse macrophages.