POLYMYXIN-B STIMULATES PRODUCTION OF COMPLEMENT COMPONENTS AND CYTOKINES IN HUMAN MONOCYTES

Polymyxin B (PmB), an agent often used to neutralize the effects of ba cterial lipopolysaccharide (LPS), was shown to exert a dose-dependent stimulatory effect on the biosynthesis of C3, factor B, interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in human monocytes. A low dose of PmB (1 to 5 mu g/ml) efficiently sup pressed the LPS-induced (1 or 100 ng/ml) production of IL-6, GM-CSF, a nd factor B, but not the C3 production induced by 100 ng of LPS per ml . A reduced level of GM-CSP may have contributed to the persisting hig h C3 concentrations and the apparent lack of LPS inhibition in the lat ter situation, since GM-CSF is an inhibitor of monocyte C3 biosynthesi s.