Influence of Chlorpyrifos, an Organophosphate Insecticide, on the Immune System of Nile Tilapia

Abstract

Recent reports about laboratory rodents indicate that parameters of the immune system, including total immune cell number in hematopoietic compartments and ability to elicit both specific and nonspecific immune responses, may be among the most sensitive indicators of environmental contaminant exposure. In several species of wild-caught and laboratory-exposed fish, altered monocyte chemotactic ability, chemiluminescent responses (metabolic oxidative burst), and phagocytosis have recently been found to be associated with exposure to polycyclic aromatic hydrocarbons and organometals, indicating that parameters of immunity may also served as potential sensitive markers of chemical exposure in fish. In the present experiments, Nile tilapia Oreochromis niloticus exposed to the organophosphate insecticide, chlorpyrifos, at a concentration of 1 μg/L displayed significantly lower total pronephros cell counts than did untreated controls. In addition, macrophages isolated from the pronephros of the treated fish had depressed phagocytic function relative to control fish. These data suggest that fish exposed to environmentally relevant levels of chlorpyrifos may be immunologically altered. Further, results of our study provide additional evidence that parameters of immune function may serve as sensitive biomarkers in fish exposed to environmental contaminants.