Immunotoxicity of technical pentachlorophenol (PCP-T): depressed humoral immune responses to T-dependent and T-independent antigen stimulation in PCP-T exposed mice.

The effects of chronic dietary exposure to technical pentachlorophenol (PCP-T) on humoral immune responses in mice were examined. Primary and secondary splenic antibody responses to the T-dependent antigen, sheep red blood cells (SRBC), were examined in Swiss-Webster mice using our recently developed screening technique, the Hemolytic Antibody Isotope Release (HAIR) assay. To assess direct effects of PCP-T on B cells, the splenic plaque-forming cell response and serum antibody titers to the T-independent antigen, dinitrophenyl (DNP)-Ficoll, were examined. PCP-T exposure altered both the kinetics and the magnitude of the humoral antibody responses to SRBC and DNP-Ficoll. Peak splenic antibody production and serum antibody titers were delayed and the magnitude of the antibody responses were dose-dependently suppressed by PCP-T exposure. IgM responses appeared to be more sensitive to PCP-T-induced suppression than the IgG response. Significant depression of the IgM anti-SRBC splenic HAIR response was apparent as early as 2 weeks after initiation of PCP-T exposure and persisted for at least 8 weeks after termination of PCP-T feeding. Liver weight and serum lactate dehydrogenase (LD-L) and alanine aminotransferase (ALT) levels were significantly elevated during PCP-T exposure and returned to control levels after a 4-6 week recovery period. The immunotoxic effect of PCP on humoral immunity was observed only in animals exposed to technical grade PCP known to be contaminated with significant levels of other chlorinated phenols as well as non-phenolic impurities including chlorinated dioxins, furans, and diphenyl ethers. Animals exposed to analytical grade PCP did not exhibit depressed humoral immunity.