Differentiation of Rat Bone Marrow Cells Into Macrophages Under the Influence of Mouse L929 Cell Supernatant

Bone marrow cells (BMC) flushed from femora of Lewis rats were cultured in Dulbecco’s modification of Eagle’s medium supplemented with mouse L929 cell supernatant as a source of colony-stimulating factor (CSF). Differentiation of macrophage progenitor cells into macrophages (M4) and expression of various markers were kinetically assessed. The proportion of Mf increases from approximately 4 % In freshly isolated BMC to 100% after 7-8 days of cell culture. These cells, termed bone marrow cell-derived macro-phages (BMDMI5), adhere to and spread on plastic surface; exhibit M morphology; stain Intensely for nonspecific esterase; are able to phagocytose latex particles, IgG-sensi-tized erythrocytes, and C3-coated red cells; and express receptors for lgG and C3. A subpopulation of BMDM expresses MHC class II antigens as demonstrated by immu-nofluorescence using MRC 0X6 and MRC 0X17 monoclonal antibodies which recognize antigens coded in the I-A or l-E subregion of the MHC, respectively. Collectively, our results show that supernatant from mouse L929 cells supports and Is continuously required for proliferation and differentiation of rat BMC into typical M4, and suggest that mouse CSF cross-reacts with the putative receptor on rat Mf. Key words: CSF, Fc receptor