Combined effects of selected insecticides on humoral immune response in mice.

Biological effects data with single insecticides are far more abundant than with mixtures. These data cannot be used directly to predict the effects of insecticide mixtures. Three insecticides of different chemical classes: organochlorine; dieldrin, organophosphate; malathion, and carbamate; carbofuran, previously evaluated for their immunotoxic potential, were selected for studies of combined acute exposure in C57B1/6 inbred mice. The humoral response to sheep red blood cells (SRBC) and the functional activities of peritoneal macrophages, such as phagocytosis of fluorescent beads and presentation of a single protein antigen, avidin, were examined after in vivo exposure of mice to different combinations of the selected pesticides and compared with the vehicle controls. Regarding exposure to single substances, the data confirmed the immunosuppressive potential of dieldrin and carbofuran and the immunopotentiating effect of malathion. Following the acute concomitant exposure to dieldrin/carbofuran mixture, however, values for the parameters of antigen presentation, primary IgM antibody response to SRBC antigen, and macrophage phagocytosis, returned to control or above-control values, indicating a lack of any synergistic or additive effects of the chemicals on the immune response. Thus, it was concluded the dieldrin/carbofuran mixture had an antagonistic effect on the humoral response to SRBC and the macrophage phagocytic activity, in comparison with the action of administration of each of the insecticides alone.