Effects of chlorinated phenols on immunity in rats.

Female Sprague - Dawley rats were exposed to 0, 5, 50 or 500 ppm 2-chlorophenol (2-CP) or pentachlorophenol (PCP) from weaning to 3 weeks postparturition after breeding at 90 days of age. Progeny were weaned at 3 weeks of age and continued on chlorophenol treatment for 10 weeks at which time major immune functions were tested. Humoral immunity was measured by an indirect ELISA, cell-mediated immunity was monitored by delayed-type hypersensitivity (DTH) to oxazolone, and macrophage function was tested by phagocytosis of sheep red blood cells. Rats treated with cyclophosphamide were included as a positive immunosuppressed control. PCP-treated rats had significantly decreased antibody titers and DTH response and increased induced peritoneal macrophage numbers which displayed hyperphagocytic activity. Immune responses in rats treated with 2-CP were not significantly different from controls. The data indicate that (1) the immune system may be a sensitive target for PCP toxicity but not for 2-CP, (2) closely related chlorophenolic chemical isomers may exert different toxic effects on the immune system, and (3) PCP can exert depressive effects on some major immune parameters while enhancing others.