Comparison of the T Cell-Independent Antibody Response of Mice and Rats Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant that produces adverse effects on the immune system of experimental animals. In this study, the effect that TCDD has on the antibody plaque-forming cell (PFC) response to the T cell-independent (TI) antigen trinitrophenyl-lipopolysaccharide (TNP-LPS) was compared in adult female B6C3F1 mice and F344 rats. Mice or rats were given a single intraperitoneal injection of TCDD at doses ranging from 1 to 30 micrograms/kg, 7 days prior to immunization with TNP-LPS by intravenous injection. Three days later body, spleen, thymus, and liver weights were measured and the PFC response to TNP-LPS was determined. Thymus weights were decreased at 10 and 30 micrograms TCDD/kg, whereas spleen weights were decreased and liver weights increased in mice dosed at 3, 10, and 30 micrograms/kg. Mice dosed at 10 and 30 micrograms TCDD/kg had suppressed PFC responses and serum hemagglutination titers. In rats, thymus weights were decreased and liver weights increased at 3, 10, and 30 micrograms TCDD/kg; however, the PFC response and serum hemagglutination titers to TNP-LPS were suppressed only at 30 micrograms/kg TCDD. TCDD did not affect splenic lymphocyte subsets evaluated by flow cytometry. These results indicate that TCDD suppresses the TI antibody response to TNP-LPS in both B6C3F1 mice and F344 rats, with mice more sensitive to suppression by TCDD than rats.