GRASMAN, K.A.: Assessing Immunological Function in Toxicological Studies of Fish-Eating Birds

Persistent organochlorine contaminants, especially polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachloro-p-dioxin (TCDD), have been shown to suppress immune function in rodents and chickens in the laboratory. Fish-eating birds are exposed to high levels of organochlorines in some ecosystems. Our objective was to assess the effects of organochlorines on immune function of young wild herring gulls (Larus argentatus) and Caspian terns (Sterna caspia) from the Great Lakes and black guillemots (Cepphus grylle) from Labrador. Immunological status was assessed in 3-4 week old chicks using general indicators (white blood cell counts and immune organ masses) and specific tests of immune function (the phytohemagglutinin (PHA) skin test for T cell function and the anti-sheep red blood cell (SRBC) antibody test for humoral immune function). An intradermal injection of PHA into the wing web was used to stimulate a T cell dependent reaction that was measured 24 h after injection. An intravenous injection of SRBC was used to stimulate an antibody response that was measured in plasma 6 days after immunization. In all three species, suppression of the PHA test was strongly associated with organochlorine exposure. This suppression of T cell function was consistent with thymic atrophy observed in guillemot chicks and herring gull chicks and embryos. In Caspian tern chicks, the antibody response was positively associated with PCBs and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE). These immune function tests can be adapted to a broad range of species and have proven to be feasible in toxicological and physiological studies of wild birds.