| The primary goal of this investigation was to describe the systemic and immunopathologic effects of chronic, low concentration petroleum oil exposure in American mink (Mustela vison), a model for the sea otter. Even in the absence of an oil spill, petroleum hydrocarbon contamination may present a significant health risk to the Southern sea otter (Enhydra lutris nereis). A second goal was to develop the immunological tools to study the sea otter immune system.; Thirty mink were divided into fuel oil-fed (n = 20) and control (n = 10) groups. Half the animals in each group received a foreign antigen injection. Hematologic parameters, organ weights, gross and histologic tissue examination, peripheral blood immunophenotype, mitogen-stimulated mononuclear cell proliferation, hepatic CYP 1A1 and fecal cortisol concentrations were evaluated. We observed alterations in erythrocyte and leukocyte numbers, increased liver weight, activation of hepatocellular metabolism, adrenal gland hypertrophy, and decreased mesenteric lymph node weight in association with fuel oil exposure. Immunophenotype analysis showed a mild yet significant increase in the absolute numbers of specific leukocyte subsets and an increase in the level of expression of functional surface proteins. We also observed an increase in mononuclear cell proliferation. This is the first time to our knowledge that this unique profile of systemic and immunological changes has been identified with chronic exposure to fuel oil. Our results suggest that fuel oil exposure induces a pro-inflammatory effect and may act as an adrenal endocrine disruptor neither of which had been previously identified in vivo associated with chronic fuel oil exposure. In parallel to our studies in mink, we adapted similar immunological tests for use in Southern sea otters. We established normal ranges for adult sea otters for immunophenotype and for lymphocyte function (proliferation and IL-2 receptor expression) in peripheral blood. Significant age-related changes were observed in B lymphocyte numbers and MHC II expression between adult animals and pups. In addition, these immunological tests detected subtle differences in response between individuals. Our results suggest that immunological assessment provides valuable information not detectable by traditional health screening tests, and therefore, should be included with tests currently used to study sea otter health. |
