Effects of sex steroids on innate and adaptive immunity

Abstract

Estrogens and androgens are classically recognized as reproductive sex steroid hormones because of their well-documented effects on reproductive tissues. However, extensive research in diverse biological disciplines have clearly established that reproductive hormones have broad physiological effects on nonreproductive tissues, including the immune, central nervous, cardiovascular, and skeletal systems. Thus, the term sex/reproductive hormones describes only a narrow (albeit important) aspect of biological effects of sex steroids. In this chapter, the effects of sex hormones on the innate and adaptive immune system are highlighted. Generally, estrogens upregulate proinflammatory cytokines (e.g., IFNγ) and IFNγ-inducible molecules (nitric oxide, NOS2, and COX2), whereas androgens suppress proinflammatory responses. Immunomodulation by sex steroids may have both physiological and pathological implications (e.g., sex differences in immune capabilities and in inflammatory diseases, respectively).