2,3,7,8-Tetrachlorodibenzo- p-dioxin and natural immunity: lack of an effect on the complement system in a guinea pig model

We examined the complement system as a potential target for toxicity of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in normal Hartley guinea pigs. Guinea pigs were injected intravenously with 0.5 μg/kg TCDD and bled at weekly intervals up to 1 month following injection. Serum samples were collected at each time point and assayed for total hemolytic complement activity (CH50), alternative pathway complement activity (AH50) and complement component C4 functional activity. Injection of TCDD led to a wasting syndrome, as observed by a lower body weight gain in TCDD-treated animals when compared to control animals. However, at this dose, TCDD failed to induce any significant change in complement activity as determined by all three methods used in this study. The results indicate that, at 0.5 μg/kg body weight, a dose slightly lower than the LD50 value in guinea pigs, TCDD fails to affect the complement system.