Antibody-mediated immunotoxicity in American kestrels (Falco sparverius) exposed to polychlorinated biphenyls

Antibody-mediated immune function in adult and recently fledged (30 to 33 d old) American kestrels (Falco sparverius) was examined in birds exposed directly, or only in ovo, to polychlorinated biphenyls (PCBs). In 1998, 9 mature male and 9 female kestrels were fed PCBs, whereas 9 females and 10 males served as controls. A mixture of Aroclors 1248:1254:1260 suspended in safflower oil was injected into the kestrels' food items, while in control diets only the same volume of oil was added. The dosage of PCBs was approximately 7 mg/kg kestrel/d, beginning in March 1998 and continuing for 120 d. In 1998, the antibody-mediated immune response was stimulated by immunization and booster vaccinations of the kestrels using a nonpathogenic antigen, dinitrophenol-keyhole limpet hemocyanin (DNP-KLH). In 1999, offspring from three treatment groups based upon maternal exposure to PCBs were similarly tested for their antibody response. None of these mothers was vaccinated with DNP-KLH the previous year. The maternal groups were: (1) exposed to PCBs in 1998 for 120 d, (2) exposed in ovo in 1998 (i.e., mothers were produced by PCB-exposed parents), or (3) unexposed to PCBs. Serum antibody levels were determined using an enzyme-linked immunosorbent assay (ELISA). In 1998, PCB-exposed adult females had a significantly higher antibody response than did controls, whereas adult males exposed to PCBs had significantly suppressed antibody production. For the nestlings produced in 1999, maternal treatment significantly affected antibody response. Generally, the antibody response in the nestlings was much lower than that seen in adult kestrels. Yet both male and female offspring from mothers that had been fed PCBs the previous year had significantly higher postbooster anti-DNP-KLH titers than control and in ovo-exposed maternal groups, thus mimicking the response seen in the adult females the previous year. These sex-specific responses in PCB-exposed birds provide further evidence of the endocrine-disrupting behavior of PCBs. Both suppression and stimulation of the antibody response are undesirable because this indicates that the immune system is not able to respond normally to challenges by infectious or other disease-causing agents.