Journal of Leukocyte Biology 38:509-520 (1985) Kl-M2R, a New Specific Monoclonal Antibody, Discriminates Tissue Macrophages From

Utilizing rat peritoneal macrophages as the immunogen, a new monoclonal antibody enabling differential monitoring of the mononuclear phagocyte sys-tem (MPS) by immunohistochemistry has been raised. Designated Ki-M2R, this antigen could be detected with the immune alkaline phosphatase reaction on all macrophages including those of bone marrow, lymphatic sinuses, lymph-oid follicles, splenic red pulp, and von Kupffer cells of the liver, as well as on macrophages of connective tissue, renal interstitial tissue, serous cavities, and gastrointestinal tract. Langerhans cells-the MPS-derived reticulum cells of the epidermis-interdigitating reticulum cells, and dendritic reticulum cells of lymphoid follicles were invariably negative. Blood monocytes were rendered positive only after evolving into macrophages upon appropriate stimulation. Thus, Ki-M2R selectively labels monocytes after transformation into mac-rophages. Key words: monoclonal antibody, macrophages, reticulum cells, monocyte