The characterization of early branch points in the differentiation of leukocytes requires identification of precursor cells in the bone marrow. Recently, we produced two monoclonal antibodies, ER-MP12 and ER-MP20, which in two-color flow-cytometric analysis divide the murine bone marrow into six defined subsets. Here we show, using fluorescence-activated cell sorting followed by macrophage colony-stimulating factor-stimulated culture in soft agar, that precursors of the mononuclear phagocyte system reside only within the ER-MP12hi20−, ER-MP12+20+ and ER-MP12−20hi bone marrow subsets. Together, these subsets comprise 15% of nucleated bone marrow cells. Furthermore, we provide evidence that the macrophage precursors present in these subsets represent successive stages in a maturation sequence where the most immature ER-MP12hi20− cells develop via the ER-MP12+20+ stage into ER-MP12−20hi monocytes.

Heterogeneity, Macrophage, Phenotype, Progenitor,
European Journal of Immunology

de Bruijn, M.F.T.R, Slieker, W.A.T, van der Loo, J.C.M, Voerman, J.S, van Ewijk, W, & Leenen, P.J.M. (1994). Distinct mouse bone marrow macrophage precursors identified by differential expression of ER-MP12 and ER-MP20 antigens. European Journal of Immunology, 24(10), 2279–2284. doi:10.1002/eji.1830241003