EARLE, Kristen A.*; ROMERO, L. Michael; Tufts University; Tufts University: Effects of chronic stress on the cell-mediated immune response in European Starlings (Sturnus vulgaris)

Both chronic stress and heightened levels of the stress hormone corticosterone have been shown to suppress the cell-mediated immune response. In this study 8 European starlings (Sturnus vulgaris) were stressed for 20 days and their immunity was assessed via inflammatory response to the T-cell mitogen phytohaemagglutinin (PHA). PHA was injected intradermally into the wing web on one side, and saline was injected intradermally into the contralateral wing web. The difference in swelling due to PHA was compared to the difference in swelling sustained by 8 control unstressed starlings. At 24 hours, PHA induced equivalent swelling in both groups. In contrast, the unstressed birds sustained swelling for 48 hours whereas swelling decreased, but did not recover, in the chronically stressed birds. These data suggest that unstressed birds sustain a longer T-cell response than chronically stressed birds. Additionally, baseline levels of corticosterone have been shown to be lower after chronic stress, suggesting that corticosterone may not be responsible for the suppression of cell-mediated immunity in chronically-stressed starlings.