Environmental chemical-induced immune dysfunction.
Antibody formation, endotoxin sensitivity, and resistance to a challenge malarial infection were evaluated in mice fed a diet containing polychlorinated biphenyl (PCB) (Aroclor 1242) or hexachlorobenzene (HCB). Antibody synthesis to the antigen sheep RBC (SRBC) was significantly depressed in the PCB- and HCB-treated (167 ppm) animals as evidenced by the fact that control mice elicited an approximate twofold increase in antibody formation over the chemical-treated mice. Serum IgA concentrations in the PCB- and HCB-treated mice were consistently 40--80 mg/dl lower than control values. Gram-negative endotoxin (Salmonella typhosa) sensitivity in PCB- and HCB-treated mice was increased 5.2- and 32-fold, respectively, following the dietary administration of 167 ppm of Aroclor 1242 or HCB for 6 weeks. An endotoxin hypersusceptibility was also noted at 3 weeks after dietary administration. Decreased resistance to a malaria challenge was also demonstrated in the xenobiotic-treated mice. A 20% decrease in mean survival time of mice fed Aroclor 1242 for 3 to 6 weeks and inoculated with Plasmodium berghei (NYU-2) was observed. Infected mice which had received HCB for 3 or 6 weeks manifested reductions in mean survival time of 24 and 31%, respectively. The data indicated that environmental chemical contaminants impair host resistance and, since no concomitant histopathological alterations were observed in the treated mice, the evaluation of immune parameters may possibly be a sensitive indicator of toxicity.