The immunomodulatory effects of the herbicide simazine on murine macrophage functions in vitro.

We examined the immunomodulating effects of simazine, a triazine herbicide, on murine peritoneal macrophages after in vitro pre-exposure. When thioglycollate-elicited macrophages pre-exposed to simazine were stimulated with lipopolysaccharide (LPS), the antitumor activity induced by LPS was suppressed by simazine. Simazine also inhibited poly I:C-induced antiviral activity and interferon (IFN) production in macrophages. In addition, the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) which have been known to be major effector molecules in macrophage-mediated cytotoxicity was decreased by simazine pretreatment in a dose-dependent manner. However, simazine had little effect on phagocytosis and the level of hydrogen peroxide (H(2)O(2)), interleukin-1 (IL-1) and IL-6 by LPS-stimulated macrophages. Taken together, these data indicate that simazine has a differential immunomodulating effect on macrophage secretory and cellular activities.