Modulatory effect of antibiotics on cytokine production by human monocytes in vitro

Some antimicrobial agents have been reported to modify the host immune and inflammatory responses both in vivo and in vitro. Fosfomycin (FOM) and clarithromycin (CAM) have immunomodulatory activity on human lymphocyte function. In the present study, we examined the effects of FOM and CAM on cytokine synthesis by lipopolysaccharide (LPS)-stimulated human monocytes in comparison with that of dexamethasone in vitro. The three drugs demonstrated positive or negative effects on the synthesis of various cytokines by LPS-primed monocytes. They suppressed the synthesis of tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-1 beta, the IL-1 receptor antagonist, and granulocyte-macrophage colony-stimulating factor in a concentration-dependent manner at concentrations between 1.6 and 40 micrograms/ml. On the contrary, the drugs showed different actions on the synthesis of IL-6 and IL-10. Namely, FOM enhanced both IL-6 and IL-10 synthesis, CAM enhanced only IL-10 synthesis, but dexamethasone deeply suppressed the synthesis of both cytokines. These data indicate that antibacterial agents may modify acute-phase inflammatory responses through their effects on cytokine synthesis by monocytes.