Inhibited Cytotoxic Leukocyte Activity in Tilapia (Oreochromis niloticus) Following Exposure to Immunotoxic Chemicals

Abstract

The measure of the ability of cytotoxic immune cells to target and lyse foreign cells has been widely used as a predictor of im-munosuppression in chemical-exposed rodents. However, the efficacy of this function for predicting immunosuppressive chemical exposure in nonrodent species remains unknown. In the present report, tilapia ( Oreochromis niloticus) were exposed to 9 chemical agents known to inhibit rodent cytotoxic T lymphocyte (CTL) activity in mice, benzo[a]pyrene (B[a]P), 7, 12-dimethylbenzanthracene (DMBA), 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), dimethyl-nitrosamine (DMN), cadmium chloride (CdCl2), azathioprine (AZA), T2 mycotoxin (T2 toxin), hexachlorocyclohexane (lindane), and diethylstilbesterol(DES); and five chemical agents which do not inhibit this response, oxymethalone, acetonitrile, tert-butylhydro-quinone (TBHQ), toluene, and formaldehyde. Eight of the nine agents which inhibit rodent CTL responses also caused decreased cytolytic responses in fish. All five of the compounds with negative CTL effects in rodents were also negative in fish. Thus, 13 of the 14 chemical agents tested gave similar results in fish as reported in rodents, indicating a comparable pattern of inhibited immune cell cytolytic responses in chemical-exposed tilapia to that seen in the laboratory rodent models.