Host defense systems in cattle exposed to polybrominated biphenyl

Area of Science:

• Veterinary immunology
• Toxicology
• Environmental health

Background:

• Polybrominated biphenyls (PBBs) are persistent organic pollutants with potential immunotoxic effects.
• Assessing the impact of PBBs on bovine immune competence is crucial for animal health and food safety.

Purpose of the Study:

• To evaluate the effects of PBB exposure on the immune system of Holstein cattle.
• To determine the threshold of PBB body burden associated with immune dysfunction.

Main Methods:

• In vivo and in vitro immunologic studies were conducted on 114 Holstein cattle.
• A comprehensive immunologic test profile assessed serum immunoglobulins, autoantibodies, lymphocyte subpopulations, lymphoblastogenesis, delayed hypersensitivity, and neutrophil function.
• PBB concentrations in adipose tissue were measured.

Main Results:

• Cattle with PBB body burdens from 0.02 to 24.0 mg/kg showed intact host defenses in quantity and function for at least 2 years.
• Acute toxicity studies revealed normal immune competence in cattle fed 25 g of PBB daily until accumulating 500 g (tissue concentrations >1,000 mg/kg).
• Cattle fed over 500 g of PBB became moribund, exhibiting altered neutrophil function and serum antibody titers.

Conclusions:

• Bovine immune competence remains largely intact at environmentally relevant PBB body burdens.
• Significant PBB accumulation is required to induce detectable immunotoxicity in cattle.
• These findings inform risk assessment for PBB exposure in livestock.