The fact that gender influences the immune system has long been recognised. The higher risk of women developing autoimmune diseases suggests that these are somehow mediated by sex steroids, with estrogens as enhancers at least of the humoral immunity and androgens and progesterone as natural immune-suppressors. The concept of immunosenescence reflects changes in both cellular and humoral immune responses. This may be related with the higher incidence of infectious and chronic diseases. Besides age, in postmenopausal women, changes of the immune system have been attributed to estrogen deprivation. There is an increase in pro-inflammatory serum markers, an increasing response of the body's cells to cytokines, a decrease in CD4 T and B lymphocytes and in the cytotoxic activity of NK cells. In fact IL-6 is a key factor in bone reabsorption by osteoclast activation and also seems to be associated with diseases that occur more in menopause such as diabetes, atherosclerosis and cardiovascular diseases. Recent studies indicate several changes in immune response, either with suspension of hormone therapy or with its replacement at menopause.