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PM11 Wildlife Ecotoxicology
(PM194) Comparison of mitogen-induced lymphocyte proliferation of loggerhead sea turtles after in vivo and in vitro exposure to PCBs and 4,4'-DDE.
Keller, J1, Kucklick, J1, Arendt, M2, Maier, P2, Segars, A2, Whitaker, J2, Peden-Adams, M3, 1 National Institute of Standards and Technology, Charleston, SC, USA2 South Carolina Department of Natural Resources, Charleston, SC, USA3 Medical University of South Carolina, Charleston, SC, USA
ABSTRACT- Organochlorine contaminants, such as PCBs and DDT metabolites, are known immunotoxicants. Blood concentrations of these compounds in threatened loggerhead sea turtles (Caretta caretta) were previously found to be positively correlated to immune function, measured by mitogen-induced lymphocyte proliferation (LP). In this study, blood leukocytes from eight loggerhead turtles were exposed in vitro to Aroclor 1254 (1-15000 ng/mL) and 4,4'-DDE (0.1-15000 ng/mL). Cells were stimulated with four different mitogens: 20 g/mL concanavalin A (ConA) and 5 g/mL phytohemagglutinin (PHA) for T-cell proliferation and 10 g/mL lipopolysaccharide (LPS) and 0.2 g/mL phorbol 12,13-dibutyrate (PDB) for B-cell proliferation. Cell viability was tested and LP was measured using 3H-thymidine after five days of simultaneous mitogen and contaminant exposure. Viability was affected at only the highest concentration of both contaminants. No significant contaminant effect was observed on ConA- or LPS-induced LP, likely because these mitogens are not very effective at eliciting LP in the loggerhead. PHA-induced LP was increased at 100 ng/mL Aroclor 1254 and 1000 ng/mL 4,4'-DDE and was suppressed at 15000 ng/mL Aroclor 1254. PDB-stimulated LP was increased at 5 ng/mL Aroclor 1254 and at 0.1 and 0.5 ng/mL 4,4'-DDE and was suppressed at 50, 500, and 1000 ng/mL Aroclor 1254. These in vitro experiments corroborate correlations observed in vivo, in which PHA-stimulated LP was strongest in turtles that had the highest blood concentrations of total PCBs (up to 23.9 ng/g). Likewise, the five turtles with the strongest PDB-stimulated LP (out of 16 turtles examined) had blood concentrations of 4,4'-DDE between 0.675-1.13 ng/g, similar to concentrations that caused the peak LP responses in vitro. The results from the in vitro experiments match the in vivo observations, providing more evidence that organochlorine contaminants affect loggerhead turtle immunity.
Key words: PCBs, immune function, DDT, reptiles
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