Non-reproductive effects of sex steroids: their immunoregulatory role

Sex hormones play an important role as modulators of the immune system. A growing body of evidence shows reciprocal relationship between sex steroids and the immune system. Since the innate immune response determines the type of adaptive immune response, hormonal effects on the innate immune response may affect subsequent adaptive immunity. The sex steroids estrogens, progesterone and testosterone regulate growth, differentiation, survival and function of many cell types involved in homeostasis and immunity. The presence of sex steroid receptors on immune cells indicates that sex steroids may exert their biological effects by binding to these receptors. Sex steroids and immunity are closely connected, and their mutual regulation is involved in the maintenance of immune balance. Understanding the mechanisms of action of sex steroids on immune cells is important for further progress in the development of novel therapies for chronic diseases associated to immune dysregulation. This review describes the effects of sex steroids on the different immune system cells, and the possible implications of these effects on the incidence of many diseases.