The effect of colony stimulating factor-1 in vivo

The present studies were undertaken to determine whether colony stimulating factor-1 (CSF-1) stimulates hemopoietic cell proliferation and differentiation in vivo. Groups of mice were injected with 25,000 units of pure, endotoxin-free L-cell CSF every 6 hours for intervals up to 8 days. Virtually no changes were detected in blood neutrophils or monocytes. No consistent increases in marrow granulopoiesis were noted. Variable but inconsistent changes in marrow and splenic progenitor cells were noted. Serum CSF was elevated 2 hours after injection but returned to baseline values within 4-6 hours. These studies indicate essentially no effect from exogenous administration of purified CSF; however, higher doses of this factor will be required in further studies.