Abstract

This immunologic study was part of a larger program directed at defining potential associations between environmental contaminants and the health of the free-ranging bottlenose dolphin (Tursiops truncatus) population in Sarasota Bay, Florida. The immunologic effects of the short-term capture-associated stress were assessed in 26 dolphins; a wide range in animal age was represented. Blood samples were obtained immediately after capture and then again just prior to release; the time from the 1st to 2nd bleed ranged from 1.3 to 3.3 hours. The immune system is extremely sensitive to perturbation and, as such, is an excellent measure of animal health, including presence of stress. The immune panel data applied to the paired dolphin blood samples included the following: a) a complete blood cell count (CBC), b) flow cytometry analysis of lymphocyte subpopulations including total T lymphocytes (express CD2), naïve versus memory T lymphocytes (differential expression of CD45R on CD2-expressing lymphocytes), and B lymphocytes (expression of CD21 and CD19), c) leukocyte surface density of adhesion proteins using analytical flow cytometry, d) clinical chemistries, e) fibrinogen, f) serum cortisol, g) systemic levels of the acute phase protein interleukin-6 (IL-6) and h) lymphocyte function by mitogen-induced proliferative response (blastogenesis assay). Differentiation between lymphocyte dysfunction and stress-associated reduction in lymphocyte proliferative responses was approached using two concentrations of each of three mitogens in a lymphocyte proliferation assay. Taken together, such data are useful in determining the presence of immune system dysfunction, leukocyte abnormalities and/or infectious disease/inflammation. While individual animal variability probably masked some capture-associated immunologic changes, certain perturbations were easily identifiable. Relative to the 1st bleed, total white blood cell counts were decreased at the 2nd bleed. This reduction was due to a decrease in eosinophils (23 of 26 animals) and neutrophils (18 of 26 animals); total numbers of lymphocytes were variable with some increasing, some decreasing and some staying constant. Analysis of leukocytes by flow cytometry demonstrated a dramatic decrease in the apparent cell-surface density of CD19 on B lymphocytes. Relative to analysis of serum, elevated levels of cortisol and glucose were very obvious at the 2nd bleed. No consistent changes in lymphocyte function have been identified between the 1st and 2nd bleeds. Further analysis is in progress to identify potential associations between the extent of animal handling and immunologic perturbation. In addition, future studies are planned to include immunologic analysis of animals recaptured at 24 to 48 hours.

Acknowledgments

Supported by the Office of Naval Research, National Marine Fisheries Service, International Whaling Commission, Laboratory for Marine Mammal Immunology at UC-Davis, Chicago Zoological Society and Dolphin Quest