| Contaminant-related Suppression of Delayed-type Hypersensitivity and Antibody Responses in Harbor Seals Fed Herring from the Baltic Sea Peter S. Ross,1,2 Rik L. De Swart,1 Peter J.H. Reijnders,3 Henk Van Loveren,2 Joseph G. Vos,2 and Albert D.M.E. Osterhaus1,2 1Seal Rehabilitation and Research Centre, 9968 AG Pieterburen, The Netherlands;
2National Institute of Public Health and Environmental Protection, 3720 BA Bilthoven, The Netherlands;
3DLO-Institute for Forestry and Nature Research, 1790 AD Den Burg, The Netherlands Abstract
Recent mass mortalities among several marine mammal populations have led to speculation about increased susceptibility to viral infections as a result of contaminant-induced immunosuppression. In a 2.5-year study, 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 contaminated fish were less able to mount a specific immunological response to ovalbumin, as measured by in vivo delayed-type hypersensitivity (DTH) reactions and antibody responses. The skin reaction to this protein antigen was characterized by the appearance of mononuclear cells which 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 cell type in the reaction. Aryl-hydrocarbon (Ah) receptor-dependent toxic 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 inhabiting polluted coastal environments in Europe and North America may therefore have an increased susceptibility to infections, and pollution may have played a role in recent virus-induced mass mortalities. Key words: delayed-type hypersensitivity, harbor seals, immunosuppression, organochlorines. Environ Health Perspect 103:162167 (1995) http://ehpnet1.niehs.nih.gov/docs/1995/103p162-167ross/abstract.html Address correspondence to A.D.M.E. Osterhaus, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands. R.D. is currently at Erasmus University. The assistance of many individuals is gratefully acknowledged: Lies Vedder and all the staff of the Seal Rehabilitation and Research Centre ; Paul Thompson and Harry Ross for assistance in establishing the captive group of seals ; Jan Groen with the ELISA ; Hans van Dijk for the gift of DDA ; Wim de Jong for assistance with histopathology ; Jan Dormans with photographic layout ; and Djiem Liem and Elze Ruite for toxicological analyses. P.S.R. was partially funded by a Natural Sciences and Engineering Research Council of Canada award. R.D. was partially funded by a grant from the Nederlandse Aardolie Maatschappij. Received 7 September 1994 ; accepted 1 December 1994.
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