Meeting Abstract

P3.128  Jan. 6  Effects of Social Defeat on Immune Responses in Siberian Hamsters CHESTER, E.M.*; BONU, T.; DEMAS, G.E.; Indiana University; Indiana University; Indiana University emcheste@indiana.edu

Prolonged exposure to physical stressors causes decreased immune function as a result the activation of the hypothalamo-pituitary-adrenal (HPA) axis and the subsequent release of glucocorticoids. Likewise, social interactions can affect both the endocrine and immune systems. Recent studies suggest that social stressors, such as a defeat by a conspecific, impair specific immune responses. Here we tested the effects of social defeat on immune response of Siberian hamsters (Phodopus sungorus). Experimental animals were either subjected to a daily, 10-min social defeat for five consecutive days, or placed in one of three control groups: 1) exposure to a clean cage 2) exposure to a cage with soiled bedding or 3) exposure to a same-sex conspecific separated by a partition. All animals had baseline blood samples taken and subsequently were injected with the antigen keyhole limpet hemocyanin (KLH). Blood was collected on days 5 and 10 post-immunization. A secondary injection of KLH was given three weeks after the first injection. Blood was collected on days 7 and 10 post-secondary injection. Serum was analyzed for cortisol and immunological measures, including antibodies and bacterial killing ability. Initial results suggest that antibody production was suppressed by social defeat. Social defeat appeared to affect bacterial killing as well. Serum cortisol, however, was not significantly elevated in defeated animals immediately after defeat. Together, these results suggest that social defeat affects immunity, possibly independent of HPA activation. This study contributes to the understanding of the effects of complex social behavior on physiological functions in mammals.