Abstract

This study investigated the effects of environmental toxicants on the immune system of three pinniped species: grey seals (Halichoerus grypus), hooded seals (Cystophora cristata) and ringed seals (Pusa hispida). In addition, the effects were examined and compared to the commonly used laboratory B6C3F1 mouse (Mus musculus), the common model to assess the immunotoxic potential of chemicals. The toxicants included two perfluorinated compounds (PFC): perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), compounds commonly found in a wide variety of household consumer products, including Scotchguard and Teflon. Although corporations such as 3M curtailed the use of these chemicals in the past decade, concentrations of these chemicals are high in the arctic aquatic ecosystem and have been measured in the tissues and blood of arctic pinnipeds. However, the effects of these chemicals on the immune system are poorly understood in marine mammals. The following hypothesis was tested, "PFOA and PFOS are equally immunotoxic in arctic pinniped species and the B6C3F1 mouse model," using the following objectives: 1) quantify and assess changes in mitogen-induced lymphocyte proliferation upon increasing concentrations of PFOA and PFOS, and 2) compare changes in lymphocyte proliferation among pinniped species and mouse. Lymphocytes were isolated either from the spleen (mouse), peripheral blood (hooded seal, grey seal), or mesenteric lymph node (ringed seal). Cells were exposed to increasing concentrations of either PFOA (0–1000 ppb) or PFOS (0–300 ppb) with and without the T cell mitogen ConA. Lymphocyte proliferation was measured using a BrdU ELISA after 66 hours in culture. In this study, we did observe large variations in proliferation among animals of the same species, likely a result of working with outbred populations. This likely resulted in not always detecting statistical significant effects, highlighting the need for larger sample sizes to be confident in the interpretation of results. However, in general, the pattern of effects, both in magnitude (percent change from unexposed cells) and direction (increase or decrease), was not always similar among all three pinniped species tested. For example, significant effects (p < 0.05) on hooded seal proliferation were detected more frequently, compared to grey or ringed seals, which could suggest a difference in sensitivity among the pinnipeds tested. Importantly, the mouse model did not always correctly predict the effects in all pinnipeds species. This highlights the fact that no one species can predict the effects in another, an observation we also observed in previous studies assessing the immunotoxic potential of polychlorinated biphenyls (PCBs) in marine mammals and mice. Overall, there appeared to be effects on the pinniped immune function upon in vitro exposure to PFOA and PFOS at similar concentrations found in the blood of free-ranging animals, suggesting that free-ranging animals may be at risk for immunotoxic effects upon natural exposure.

* Presenting author