RESUMEN
In vivo and in vitro immunologic studies were undertaken in 114 Holstein cattle, 60 of which had detectable polybrominated biphenyls (PBB) in adipose tissue. The tissue PBB concentrations were between 0.02 and at least 1,000 mg/kg. An immunologic test profile was used to evaluate the influence of PBB on bovine immune competence. The profile included serum immunoglobulin determinations, autoantibody studies, lymphocyte subpopulation determinations, lymphoblastogenesis assays, delayed hypersensitivity skin testing, and neutrophil function studies. The results of the evaluation indicated that the host defenses are intact, both in quantity and function, in cattle with PBB body burdens ranging from 0.02 and 24.0 mg/kg for at least 2 years. Cattle fed 25 g of PBB daily during the acute toxicity study exhibited usual immune competence until they accumulated 500 g of PBB (tissue concentrations exceeding 1,000 mg/kg). Cattle that were fed more than 500 g of PBB became moribund and exhibited changes in neutrophil function tests and serum antibody titers.