Modulatory effect on the pesticide captan on the immune response in rats and mice

The effect of short-term oral administration of captan, [N-(trimethylthio)-4-cyclohexene-1,2-carboximide] on the immune response was studied in rats and mice. Animals were fed a diet with or without 0.3% (w/w) of captan for 7, 14, 21 and 42 days. The SRBC-antibody formation was depressed by about 70% in both species after 14 days of treatment. A release of inhibition occurred in mice at day 42. In a parallel manner, the lymphoblastic stimulation of splenic cells by PHA and by LPS was studied in captan-treated mice and their controls. The stimulation by PHA of splenic cells that were mainly T cells was clearly inhibited (45%) by day 14 of captan ingestion. Thereafter, the inhibition was only partially released until day 42. B cells, stimulated by LPS, presented a decrease in stimulation in captan-treated mice, during the first week of diet (20%). Then an important increase in the stimulation of these cells occurred at day 21 (85%) followed by a return to the normal value at day 42. These results pointed out a clear depressive effect of captan-diet on the immune response of the animals. The inhibition of SRBC-antibody formation during the first stage of the treatment may be correlated to the inhibitory effect of captan on T cells, which were cooperative with B cells for the expression of SRBC-antibody synthesis. These effects were obtained at a level of captan which was considerably lower than the toxic dose.