The heterogeneity of mononuclear phagocytes in lymphoid organs: distinct macrophage subpopulations in the rat recognized by monoclonal antibodies ED1, ED2 and ED3.

In the present study, a set of three monoclonal antibodies is described, each of which recognizes cells of the monocyte-macrophage lineage in the rat. The tissue distribution, in particular in lymphoid organs, of each of the three monoclonals is determined by immunoenzyme histochemistry on cryostat sections, as well as on cell suspensions. Results show that ED1 recognizes a cytoplasmic antigen in monocytes and in most macrophages, free and fixed. ED2 and ED3 recognize membrane antigens of tissue macrophages, discriminating between distinct subpopulations of macrophages, each with a characteristic localization in the compartments of lymphoid organs. No other cell types except cells of the mononuclear phagocyte system are positive for any of the three monoclonals. Possible relations between the macrophages recognized by this set of monoclonals and dendritic cells are discussed.