Modification of the Immune Response by Organochlorine Xenobiotics

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Abstract
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 red blood cells (SRBC) was significantly depressed in the PCB- and HCB-treated (167 ppm) animals as evidenced by the fact that control mice elicited an approximate 2-fold increase in antibody formation over the chemical-treated mice. Serum Ig[immunoglobulin]A concentrations in the PCB- and HCB-treated mice were consistently 40-80 mg/dl lower than control values. Gram-negative endotoxin (Salmonella typhosa [S. typhi]) 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 wk. An endotoxin hypersusceptibility was also noted at 3 wk 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 or 6 wk and inoculated with Plasmodium berghei (NYU-2) was observed. Infected mice which had received HCB for 3 or 6 wk manifested reductions in mean survival time of 24 and 31%, respectively. Environmental chemical contaminants apparently 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.