Paradoxical effects of cadmium exposure on antibacterial antibody responses in two fish species: Inhibition in cunners ( Tautogolabrus adspersus) and enhancement in striped bass ( Morone saxatilis)

Abstract

Previous work in a marine fish, the cunner ( Tautogolabrus adspersus), showed that endocytosis of bacteria by cells in the liver and spleen was affected by 96-h exposure of the fish to cadmium at a concentration of 12 μg/mρ; however, antibody response to sheep erythrocytes was not affected. Since the latter finding was questionable because of short immunization times, and data from more than a single fish species were desirable, both the cunner and an anadromous fish, the striped bass ( Morone saxatilis), were examined for antibody responses against the bacterium Bacillus cereus in Freund's complete adjuvant during a 6- to 8-wk time period. Exposure to 12 μg/mρ cadmium caused significant inhibition of serum antibody titers (P<0.007) in cunners. Paradoxically, antibody response in striped bass exposed to 10 μg/mρ cadmium was enhanced sixfold. This enhancement was weaker but still evident when the antigen was injected 48 d after cadmium exposure. Peritoneal exudate cells from cadmium-exposed striped bass also showed more active migration through microporous filters than cells from non-exposed fish. Since the 96-h cadmium LC 50 was 26 μg/mρ for cunners and 20 μg/mρ for striped bass, the differences in antibody response could not be explained on the basis of differences in cadmium toxicity. Although geometric mean liver cadmium levels after exposure at 15°C were higher in cunners (163.8 ± 1.2μg/gm) than in striped bass (64.4 ± 1.2μg/g), cunners exposed to cadmium at 2°C had lower cadmium levels (46.4 ± 1.2μg/g) which were still effective in inhibiting antibody production at 8°C. On the other hand, striped bass not exposed to cadmium showed a strong, exponential rise in serum antibody when the temperature at immunization, 14°C, was reduced to 9°C; whereas cunners held in the same tanks exhibited a weaker, biphasic serum antibody response. Regardless of the cause (innate differences in cellular response, or better stress adaptability in an anadromous fish), the data show that chemical-stress effects on the immune system of one fish species cannot be extrapolated to another species.