Effect of acute propanil exposure on the immune response of C57Bl/6 mice.

Propanil is a herbicide that is used extensively in rice farming to kill weeds without damaging the rice plant. The immunotoxic effects of acute exposure to propanil were determined in adult C57Bl/6 female mice exposed intraperitoneally to propanil at doses of 0, 10, 25, 50, 100, 200, or 400 mg/kg body wt. One week following exposure, the immune competency of the animals was assessed. Contact hypersensitivity response (CHR), blastogenic response to T- and B-cell-specific mitogens, and mixed lymphocyte reaction (MLR) were significantly depressed only in propanil-treated animals at 400 mg/kg. However, the number of splenic antibody-producing cells was also significantly depressed in a dose-dependent manner at the lower doses of 50, 100, and 200 mg/kg. In addition, a significant reduction in the thymus weight and an increase in absolute and relative spleen weight were also measured in animals treated with 200 and 400 mg/kg. The increase in spleen weight also showed a concomitant rise in spleen cellularity. These data indicate that propanil has a dose-dependent immunotoxic effect on the adult mouse that affects primarily the humoral response.