Validation of immunotoxicology techniques in passerine chicks exposed to oil sands tailings water

Avian species, through their trophic relationships, may represent ideal ind icators for assessing environmental health. In this study several assays of immune function in young passerines are validated and compared. From 6 to 10 days of age, zebra finch nestlings (Taeniopygia guttata) were given dail y oral doses of Oil Sands tailings water (CT), an immunosuppressant dexamet hasone, or phosphate-buffered saline. At 9-10 days of age, a phytohemagglut inin (PHA) skin test of immune function was conducted; at 11 days of age, f ive chicks from each group were euthanized for gross and histopathologic ex amination of immune system organs. The remaining birds mere vaccinated with sheep red blood cells (srbc) to evaluate antibody-mediated immunity. The m ain findings were that in 10-day-old nestlings, T lymphocytes were sensitiv e to PHA stimulation, while B lymphocytes were unable to respond to srbc; t hat hematocrit was approximately 30% lower than in mature birds; that preci sion of leucocrit determination was heavily technique-dependent; that endog enous steroids increased the total leucocrit, while exogenous steroids incr eased heterophil and decreased lymphocyte counts, thus increasing H:L; that dexamethasone exposure temporarily reduced growth rate; that CT exposure s timulated germinal cell development in the bursa of Fabricius; and that dex amethazone and CT exposure were associated with decreased splenic white pul p formation. (C) 1999 Academic Press.