CONTAMINANT RELATED SUPPRESSION OF DELAYED-TYPE HYPERSENSITIVITY AND ANTIBODY-RESPONSES IN HARBOR SEALS FED HERRING FROM THE BALTIC SEA

Recent mass mortalities among several marine mammal populations have l ed to speculations about increased susceptibility to viral infections as a result of contaminant-induced immunosuppression. In a 2.5-year st udy, we fed herring from either the relatively uncontaminated Atlantic Ocean or the contaminated Baltic Sea to two groups of captive harbor seals and monitored immune function in the seals. Seals fed the contam inated fish were less able to mount a specific immunological response to ovalbumin, as measured by in vivo delayed-type hypersensitivity (DT H) reactions and antibody responses. The skin reaction to this protein antigen was characterized by the appearance of mononuclear cells whic h peaked at 24 hr after intradermal administration, characteristic of DTH reactions in other animals studied. These DTH responses correlated well with in vitro tests of T-lymphocyte function, implicating this c ell type in the reaction. Aryl-hydrocarbon (Ah) receptor-dependent tox ic equivalent (TEQ) profiles in blubber biopsies taken from the seals implicated polychlorinated biphenyls rather than dioxins or furans in the observed immunosuppression. Marine mammal populations currently in habiting polluted coastal environments in Europe and North America may therefore have an increased susceptibility to infections, and polluti on may have played a role in recent virus-induced mass mortalities.