The Journal of immunology : official journal of the American Association of Immunologists
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Monocyte/macrophage contribution of C biosynthesis is important, particularly during inflammation. Since granulocyte-macrophage CSF (GM-CSF) and macrophage-CSF (M-CSF) exert a variety of stimulatory effects on monocyte/macrophage functions in vitro, we studied their impact on the biosynthesis of the C components C3 and factor B by human monocytes in culture. GM-CSF at doses of 10 ng/ml and higher inhibited the basal C3 synthesis. ⋯ Contrary to this, M-CSF at doses of 100 U/ml and higher stimulated the synthesis of C3, whereas the basal production of factor B and the LPS-stimulated production of C3 and factor B were unaffected. Granulocyte-CSF (G-CSF) did not influence monocyte C biosynthesis, and neither anti-M-CSF nor anti-G-CSF influenced the LPS-induced C3 production. The effects of GM-CSF and M-CSF on C biosynthesis may be important in regulating the availability of C components during an inflammatory response, and these observations may also have implications for the clinical use of CSF.