Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure

Authors

  • Mary-Kate Gilbertson,

    1. Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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  • G. Douglas Haffner,

    1. Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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  • Ken G. Drouillard,

    1. Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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  • Anathea Albert,

    1. Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
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  • Brian Dixon

    Corresponding author
    1. Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
    2. Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
    • Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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Abstract

An injection study and a field study were used to investigate the hypothesis that environmental xenobiotics have the potential to alter the immune function of northern leopard frogs (Rana pipiens). Three assays, IgM-specific antibody response to keyhole limpet hemocyanin linked to dinitrophenyl (KLH-DNP), zymozan induced chemiluminescence (CL) of whole blood and the delayed-type hypersensitivity (DTH), were used to assay humoral, innate and cell-mediated immune endpoints. Sublethal doses of DDT (923 ng/g wet wt), malathion (990 ng/g wet wt), and dieldrin (50 ng/g wet wt) were used in the injection study. In all pesticide-injected groups, antibody response was dramatically suppressed, DTH reactions were enhanced, and respiratory burst was lower. When the order of administration of pesticides and antigens was reversed, no differences in immune function between the control and dosed groups were apparent, indicating that frogs exposed to pathogens prior to pesticide exposure can still respond. A field study found significant differences in immune function between frog populations in pesticide-exposed and pesticide-free locations. The antibody response and CL were suppressed and the DTH enhanced in frogs from Essex County (ON, Canada). Overall, the results suggest that exposure to these pesticides can cause both stimulatory and suppressive immune changes in adult frogs and is doing so in wild populations.

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