Effects of OK-432 on productions of tumor necrosis factor-α and granulocyte macrophage-colony stimulating factor in human normal monocytes in vitro

Effects of OK-432 on normal human monocyte functions such as phagocytosis and TNF-α and GM-CSF production as well as H2O2 production by neutrophils after stimulation with these cytokines were studied in vitro. TNF-α and GM-CSF levels were measured by ELISA and intracellular H2O2 production by flow cytometry. The results were as follows; (1) monocytes phagocytized Texas red-labeled OK-432 within 1 hr after exposure to OK-432, though TNF-α and GM-CSF were hardly ditectible at the time. (2) TNF-α levels in the medium remarkably increased approximately 3 hrs after exposure, whereas GM-CSF levels in the medium increased approximately 6 hrs after exposure to OK-432. (3) Time course of TNF-α and GM-CSF production showed different peak time distribution. GM-CSF levels, however, were much less than TNF-α levels at any time. (4) rhTNF-α and rhGM-CSF stimulated H2O2 production in normal human neutrophils. The rhGM-CSF levels required to produce H2O2 by neutrophils were higher than GM-CSF levels secreted into the medium by monocytes. We concluded that monocytes stimulated with OK-432 secreted sufficient TNF-α for neutrophils to produce H2O2, whereas GM-CSF secreted might function within the cytokine network rather than oxiradical production.