Stress, testosterone, and the immunoredistribution hypothesis

Abstract

Recent interest in parasites and sexual selection has focused attention on the paradox that the sexual displays which indicate parasite resistance in male vertebrates are triggered by testosterone, an apparently immunosuppressive hormone. We question the underlying assumption that testosterone is immunosuppressive and offer here the alternative of immunoredistribution to explain the changes in circulating leukocytes associated with male displays and elevated testosterone. First, we briefly examine three hypotheses that have attempted to resolve the testosterone immunosuppression paradox (Folstad and Karter, 1992; Hillgarth et al., 1997; Wedekind and Folstad, 1994). Although the immunoredistribution hypothesis undermines the premise of these hypotheses, there are other problems intrinsic to each one.