Flow cytometric analysis of recombinant murine GM-CSF (rmuGM-CSF) induced changes in the distribution of specific cell populations in vivo

The changes in the distribution of granulocytes, monocytes, and lymphocytes in various tissue compartments following subcutaneous (SC) administration of recombinant murine GM-CSF (rmuGM-CSF) in vivo was determined by flow cytometry in time course studies. Balb/c mice were given single, daily SC injections of 1 or 4 micrograms of rmuGM-CSF for 10 days. Flow cytometric analysis was performed on bone marrow (BMC), peritoneal exudate (PEC), and peripheral blood (PBC) cell preparations from mice treated for 1, 3, and 10 days. Dual fluorescence was employed to gate on leukocytes (T200+) and analyze for Ig+, Thy 1.2+, MAC+, and 8C5+ (granulocytes) cells. The analyses indicated that SC-rmuGM-CSF increased the percentage of 8C5+ cells in PBC after 1 day of treatment. However, significant changes in the cell composition of PEC and BMC were not observed until day 10 of treatment and included increases in 8C5+ cells and the myeloid cell population, respectively. Side scatter analysis (cell density) of PBC and PEC indicated that the percentage of the granulocytic cell population increased significantly in rmuGM-CSF treated mice. The changes observed in PEC and BMC appeared to be dose-related whereas those observed in PBC were not. These data clearly demonstrate the utility of flow cytometric analyses for detecting selective effects of cytokines on cell populations that are involved in host defense mechanisms.