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 environmentalcontaminant that produces adverse effects on the immune systemof experimental animals. In this study, the effect that TCDDhas on the antibody plaque-forming cell (PFC) response to theT cell-independent (TI) antigen trinitrophenyl-lipopolysaccharide(TNP-LPS) was compared in adult female B6C3F1 mice and F344rats. Mice or rats were given a single intraperitoneal injectionof TCDD at doses ranging from 1 to 30 µg/kg, 7 days priorto immunization with TNP-LPS by intravenous injection. Threedays later body, spleen, thymus, and liver weights were measuredand the PFC response to TNP-LPS was determined. Thymus weightswere decreased at 10 and 30 µg TCDD/kg, whereas spleenweights were decreased and liver weights increased in mice dosedat 3,10, and 30 µg/kg. Mice dosed at 10 and 30 µgTCDD/kg had suppressed PFC responses and serum hemagglutinationliters. In rats, thymus weights were decreased and liver weightsincreased at 3, 10, and 30 µg TCDD/kg; however, the PFCresponse and serum hemagglutination titers to TNP-LPS were suppressedonly at 30 µg/kg TCDD. TCDD did not affect splenic lymphocytesubsets evaluated by flow cytometry. These results indicatethat TCDD suppresses the TI antibody response to TNP-LPS inboth B6C3F1 mice and F344 rats, with mice more sensitive tosuppression by TCDD than rats.