PHA-Stimulated Immune-Responsiveness in Mercury-Dosed Zebra Finches Does Not Match Results from Environmentally Exposed Songbirds
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Dietary mercury exposure is associated with suppressed immune responsiveness in birds. This study examined the immune-responsiveness of domestic zebra finches (Taeniopygia guttata) experimentally exposed to mercury through their diet. We used the phytohemagglutinin (PHA) skin-swelling test to assay the effect of two modes of mercury exposure. Some finches received exposure to mercury only after reaching sexual maturity, while others were maintained on a mercury-dosed diet throughout life, including development. Each bird received one of five dietary concentrations of methylmercury cysteine (0.0, 0.3, 0.6, 1.2 or 2.4 ppm). In contrast to a study on wild songbirds at a mercury-contaminated site, we detected no relationship between mercury level and immunological response to PHA, regardless of mode of exposure. This result represents the first major difference found by our laboratory between wild birds exposed to environmental mercury and captive birds experimentally exposed to mercury.
KeywordsImmune responsiveness Mercury Phytohemagglutinin Zebra finch
Research was completed with oversight from the South River Science Team, a collaboration of state and federal agencies, academic institutions, and environmental interests. Funding was provided by E. I. duPont de Nemours and company. Thank you to M. Whitney and R. Ellick for technical assistance. Special thanks to all the student researchers who assisted with data gathering, particularly K. Buck, J. Ebers, J. Kihm, M. Kobiela, S. Maddux, G. Mahjoub, J. Spickler, S. Talegaonkar, and K. Wright.
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