Use of the Immune System to Investigate the Toxicity Induced by Environmental Pollutants in Fish, Amphibian, and Mammalian Species

Abstract

In recent years, there has been growing concern about the effect of environmental pollutants on the immune system. In the current study, we investigated the toxicity induced by certain environmental pollutants on the immune systems of fish, amphibians, and mice. Fish in the laboratory were tested for susceptibility to immunosuppression by treatment with 1,3-Bis (chloroethyl)-1-nitrosourea (BCNU). Immunotoxicity of the tilapian immune system was detectable using mitogen-induced proliferation assay and cell-mediated toxicity assay. Fish from various streams of the Roanoke River were tested for immunotoxicity and parasitic infection. Fish from the more polluted North Fork of the Roanoke River exhibited a stronger mitogenic response when compared to fish from the South Fork of the Roanoke River. The effect of perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), commonly referred to as dioxin, a highly toxic environmental pollutant, was tested in C57BL/6 mice. TCDD was administered on gestational day 14 and pup thymocytes were studied for apoptosis on postnatal days 2, 4, 7, 14, and 21. Perinatal exposure to TCDD decreased thymic cellularity and induced apoptosis in the thymocytes of the pups. Amphibians from polluted areas of Bermuda were similarly tested for immunotoxicity and compared with amphibians from less polluted areas. The lymphocyte responsiveness of toads from the more polluted Bermuda Biological Station of Research (BBSR) to mitogens such as lipopolysaccarhide (LPS) was significantly less than in toads from less polluted areas of Bermuda. Histological studies revealed differences in the liver and spleen tissues of the two groups. Melanomacrophage centers were prevalent in the livers of amphibians from the more polluted BBSR when compared to the less polluted Zoo site.

These data taken together encompass a broad study on the effect of environmental pollutants across species. In each study, immunotoxicity is the end result of contact with contamination, whether occurring in the environment or induced in the laboratory. These data suggest that the immune system may serve as a biomarker for pollutants present in the environment.