Effects of exposure to benzene in vivo on the murine mononuclear phagocyte system.

Exposure to benzene has been shown to decrease resistance to challenges by Listeria monocytogenes or tumor cells in mice. Alterations of T-lymphocytes have been suggested as one probable cause. Macrophages are also critical participants in resistance to Listeria and to tumor cells. We have previously shown that exposure of macrophages in vitro to benzene metabolites, but not to benzene, inhibited several functions of macrophages that are critical for host resistance. The present studies were conducted to determine the effects of exposure to benzene in vivo on the murine mononuclear phagocyte system. Treated animals received daily subcutaneous injections of benzene (800 mg/kg) for 5 days. Macrophages were obtained by lavage from the peritoneal cavity after ip injection of sterile eliciting agents. Enumeration, peroxidase histochemistry, and a series of functional assays were performed. Animals exposed to benzene displayed a decreased number of macrophages elicited by peptone injection. Specific alterations of macrophage functions included a 50% decrease of Fc-receptor-mediated phagocytosis and 70% inhibition of tumor cell cytolysis but an enhancement of TPA-stimulated H2O2 release. There was no effect on interferon-gamma stimulated expression of Ia antigen. The observations that the elicited macrophage populations were composed of newly immigrated cells and that benzene treatment was terminated 3 days before the functional analyses were performed suggest that benzene was affecting monocytes in the blood and precursor cells in the bone marrow. Alterations of macrophage functions in injection controls suggested that determining the primary effect of exposure to benzene may be complicated by the inflammation induced by treatment at the site of injection.(ABSTRACT TRUNCATED AT 250 WORDS)