Modification of bovine interferon and tumor necrosis factor production by lead in vivo and in vitro.

Dairy cows were treated orally with lead 5 mg/kg of body weight every day during 4 weeks. Blood was taken before treatment and 3, 7, 14, 21, 28 days after first dose of lead and plasma interferon (IFN) and tumor necrosis factor (TNF) titers were assayed. The ability of cow's blood leukocytes to ex vivo production of IFN and TNF was also examined. Lead exposure caused a significant increase in the plasma level of both cytokines examined. Ex vivo blood leukocytes of lead-treated cows exhibited normal, comparable to controls, production of TNF, but decreased production of virus-induced IFN. When blood leukocytes of control cows, not treated with lead were induced in vitro to produce IFN and TNF in the presence of different concentrations of lead, a significant reduction in IFN titers was observed, but enhanced production of TNF. Such differentiated effect of lead on IFN and TNF production suggests that lead can influence the immunity by disregulation of the cytokine network.