| Effects of Organochlorine Contaminants on Loggerhead Sea Turtle Immunity: Comparison of a Correlative Field Study and In Vitro Exposure Experiments Jennifer M. Keller,1,2 Patricia D. McClellan-Green,1,3 John R. Kucklick,2 Deborah E. Keil,4* and Margie M. Peden-Adams4,5,6,7 1Nicholas School of the Environment and Earth Sciences, Coastal Systems Science and Policy, and Integrated Toxicology Program, Duke University, Beaufort, North Carolina, USA; 2National Institute of Standards and Technology, Hollings Marine Laboratory, Charleston, South Carolina, USA; 3Department of Environmental and Molecular Toxicology, and Center for Marine Science and Technologies, North Carolina State University, Morehead City, North Carolina, USA; 4Marine Biomedicine and Environmental Science Center, and 5Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina, USA; 6Grice Marine Laboratory, College of Charleston, Charleston, South Carolina, USA; 7Mystic Aquarium and Institute for Exploration, Mystic, Connecticut, USA Abstract
Several laboratory and field studies indicate that organochlorine contaminants (OCs) , such as polychlorinated biphenyls (PCBs) and pesticides, modulate immune responses in rodents, wildlife, and humans. In the present study we examined the effects of OCs on immunity in free-ranging loggerhead sea turtles (Caretta caretta) . Mitogen-induced lymphocyte proliferation responses, lysozyme activity, and OC concentrations were measured from blood samples. Mitogens chosen in the lymphocyte proliferation assay were phytohemagglutinin (PHA) and concanavalin A (ConA) for T-lymphocyte stimulation, and lipopolysaccharide (LPS) and phorbol 12,13-dibutyrate (PDB) for B-lymphocyte stimulation. Lysozyme activity was significantly and negatively correlated with whole-blood concentrations of 4,4´-dichlorodiphenyldichloroethylene (4,4´-DDE) and the sum of chlordanes. Lymphocyte proliferation responses stimulated by PHA, LPS, and PDB were significantly and positively correlated with concentrations of the sum of PCBs measured in whole blood. LPS- and PDB-induced proliferation were also significantly and positively correlated with 4,4´-DDE blood concentrations. These correlative observations in free-ranging turtles suggest that current, chronic exposure to OCs may suppress innate immunity and enhance certain lymphocyte functions of loggerhead sea turtles. To further test this hypothesis, lymphocyte proliferation was measured after in vitro exposure of peripheral blood leukocytes from 16 turtles to Aroclor 1254 (0-13.5 µg/mL) or 4,4´-DDE (0-13.4 µg/mL) . Both contaminants increased PHA- and PDB-induced proliferation at concentrations below those that affected cell viability. Moreover, the concentrations that enhanced PDB-induced proliferation in vitro were similar to concentrations measured in turtles with the highest proliferative responses. The similarities between the in vitro experiments and the correlative field study suggest that OC exposure modulates immunity in loggerhead turtles. Key words: DDT, immunotoxicity, organochlorine contaminants, organochlorine pesticides, PCBs, persistent organic pollutants, polychlorinated biphenyls, reptile. Environ Health Perspect 114: 70-76 (2006) . doi:10.1289/ehp.8143 available via http://dx.doi.org/ [Online 21 September 2005]
Address correspondence to J.M. Keller, National Institute of Standards and Technology, Hollings Marine Laboratory, 331 Ft. Johnson Rd., Charleston, SC 29412 USA. Telephone: (843) 762-8863. Fax: (843) 762-8742. E-mail: Jennifer.keller@noaa.gov *Current address: University of Nevada-Las Vegas, Clinical Laboratory Sciences Program, Las Vegas, NV, USA. We thank S. Epperly, J. Braun-McNeill, and L. Avens, National Marine Fisheries Service (NMFS) , and the pound net fisherman for their help in obtaining the North Carolina turtles. We thank M. Arendt, P. Maier, A. Segars, and J.D. Whitaker, South Carolina Department of Natural Resources (SC DNR) , Marine Resources Division, for collecting the turtle samples from South Carolina, Georgia, and Florida. We also thank J. EuDaly, A. Johnson, L. Heesemann, and M. Lee for their help with the immune measurements ; L. Schwacke and T. Hulsey for statistical advice ; M. Lee and D. Owens for testosterone and sex determination ; and R. Day, P. Becker, S. Wise, M. Schantz, and K. Grasman for their critical review of the manuscript. This study was funded in part by the Morris Animal Foundation (P.D.M.-G.) , Disney Wildlife Conservation Fund (P.D.M.-G.) , Oak Foundation (J.M.K.) , Duke University Marine Biomedical Center (P.D.M.-G. and J.M.K.) , and NMFS (SC DNR turtle project) . This work constitutes scientific contribution number 156 from the Sea Research Foundation Inc. Certain commercial equipment or instruments are identified in the article to adequately specify the experimental procedures. Such identification does not imply recommendations or endorsement by the National Institute of Standards and Technology, nor does it imply that the equipment or instruments are the best available for the purpose. The authors declare they have no competing financial interests. Received 23 March 2005 ; accepted 21 September 2005.
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