AQUATIC POLLUTION-INDUCED IMMUNOTOXICITY IN WILDLIFE SPECIES

The potential for chemicals to adversely affect human immunologic heal th has traditionally been evaluated in rodents, under laboratory condi tions, These laboratory studies have generated valuable hazard identif ication and immunotoxicologic mechanism data; however, genetically div erse populations exposed in the wild may better reflect both human exp osure conditions and may provide insight into potential immunotoxic ef fects in humans, In addition, comparative studies of species occupying reference and impacted sites provide important information on the eff ects of environmental pollution on the immunologic health of wildlife populations. In this symposium overview, Peter Hodson describes physio logical changes in fish collected above or below the outflows of paper mills discharging effluent from the bleaching process (BKME). Effects attributable to BKME were identified, as were physiological changes a ttributable to other environmental factors, In this context, he discus sed the problems of identifying true cause and effect relationships in field studies. Mohamed Faisal described changes in immune function of fish collected from areas with high levels of polyaromatic hydrocarbo n contamination. His studies identified a contaminant-related decrease s in the ability of anterior kidney leukocytes to bind to and kill tum or cell line targets, as well as changes in lymphocyte proliferation i n response to mitogens, Altered proliferative responses of fish from t he contaminated site were partially reversed by maintaining fish in wa ter from the reference site, Peter Ross described studies in which har bor seals were fed herring obtained from relatively clean (Atlantic Oc ean) and contaminated (Baltic Sea) waters, Decreased natural killer ce ll activity and lymphoproliferative responses to T and B cell mitogens , as well as depressed antibody and delayed hypersensitivity responses to injected antigens, were identified in seals fed contaminated herri ng, In laboratory studies, it was determined that rats fed freeze-drie d Baltic Sea herring had higher virus titers after challenge with rat cytomegalovirus (RCMV) than rats fed Atlantic Ocean herring; perinatal exposure of rats to oil extracted from Baltic herring also reduced th e response to challenge with RCMV, Keith Grassman reported an associat ion between exposure to polyhalogenated aryl hydrocarbons and decrease d T cell immunity in the offspring of fish-eating birds (herring gulls and Capsian terns) at highly contaminated sites in the Great Lakes. T he greatest suppression of skin test responses to phytohemagglutinin i njection (an indicator of T cell immunity) was consistently found at s ites with the highest contaminant concentrations, Judith Zelikoff addr essed the applicability of immunotoxicity studies developed in laborat ory-reared fish for detecting altered immune function in wild populati ons. She presented data from studies done in her laboratory with envir onmentally relevant concentrations of metals as examples, Although the necessity of proceeding with caution when extrapolating across specie s was emphasized, she concluded that published data, and results prese nted by the other Symposium participants, demonstrate that assays simi lar to those developed for use in laboratory rodents may be useful for detecting immune system defects in wildlife species directly exposed to toxicants present in the environment. (C) 1997 Society of Toxicolog y.