Carbon tetrachloride is immunosuppressive and decreases host resistance toListeria monocytogenes and Streptococcus pneumoniae in female B6C3F1 mice

Carbon tetrachloride (CCl4) is an environmental contaminant that has been d etected in ambient air, seawater, surface-water and snow. The immunotoxic p otential of CCl4 was evaluated in female B6C3F1 mice. The animals were admi nistered with CCl4 daily for 14 days at doses of 50, 100, 500 or 1000 mg/kg body weight by gavage with corn oil as a vehicle. Exposure to CCl4 resulte d in an increase of liver weight but not the body weight and the weights of brain, spleen, lungs, thymus and kidneys. Exposure to CCl4 produced minima l effect on differential hematological parameters: however, it produced a s ignificant increase in serum glutamic-pyruvic transaminase (SGPT) levels in all dose groups while other serum chemistries showed sporadic increases, p rimarily at the dose level of 1000 mg/kg. Exposure to CCl4 produced a decre ased humoral immune response, the IgM antibody forming cell (AFC) response to sheep red blood cells (sRBC) was suppressed with the maximal decrease (4 5%) observed at the dose level of 1000 mg/kg. The IgM serum titer to sRBC w as also reduced with a maximal decrease (54%) observed at the dose level of 500 mg/kg. Although exposure to CCl4 had no effects on the mixed leukocyte response (MLR), cytotoxic T lymphocyte activity and natural killer (NK) ce ll activity, a decrease in both the absolute number and the percentage of C D4(+) CD8(-) at the dose level of 500 mg/kg was observed. The functional ac tivity of the mononuclear phagocyte system was compromised as reflected by a decrease in the vascular clearance of Cr-15-sRBC and a decrease in the up take of Cr-51-sRBC by the liver. Finally, in the two host resistance models evaluated, exposure to CCl4 decreased host resistance to both Streptococcu s pneumoniae and Listeria monocytogenes with greater susceptibility to the latter. Overall, these studies demonstrate that CCl4 was immunosuppressive in female B6C3F1 mice. (C) 2000 Elsevier Science Ireland Ltd. All rights re served.