Immunotoxicity biomarkers in fish: Development, validation and application for field studies and risk assessment

Imunocompetence is usually monitored using a tiered approach that is based upon several parameters including immunopathology, immune function, and host resistance. Through the efforts of numerous investigations, well-characterized immune assays validated in rodents for their sensitivity and reproducibility in assessing xenobiotic-induced immunotoxicity are currently available. Recently, many of these same endpoints have been utilized in non-mammalian species as indicators to predict chemical-induced immunotoxicity. In this laboratory, immune assays that measure immunopathology, antibody-forming cell response to T-dependent antigens, lymphocyte proliferation, macrophage function, antioxidant activity, and host resistance against infectious bacteria have been employed successfully to assess metal-, pesticide-, aromatic hydrocarbon-, and mixture-induced immunotoxicity in laboratory-reared Japanese medaka (Oryzias latipes). These same assays have also proven successful in feral fish populations for predicting risk(s) associated with habitation in contaminated aquatic environments. For example, smallmouth bass (Micropterus dolomieu) collected from a polychlorinated biphenyl-contaminated site had reduced phagocyte function, oxyradical production, and antioxidant levels (compared to reference fish), while circulating leukocyte profiles and lymphocyte proliferation by splenic T-cells were altered in organochlorine-exposed walleye (Stizostedium vitreum vitreum). Results of the aforementioned studies demonstrate that immune assays developed and validated in a laboratory fish model can be successfully applied to feral fish populations to predict the toxicological hazards associated with exposure to immunomodulating aquatic pollutants.