The Th1-promoting effects of dehydroepiandrosterone can provide an explanation for the stronger Th1-immune response of women.

Estrogens foster immunological processes driven by CD4+ Th2 cells and B cells and androgens foster Th1 CD4+ and CD8+ cell activity. Higher levels of IFN-gamma and IL-2 and lower levels of IL-4 and IL-10 are detected in the phytohemagglutinin-stimulated lymphocyte culture supernatants of men compared with women. It is documented that the physiologic levels of estrogens produced during the luteal phase of the menstrual cycle shift the female immune system toward a Th2-type response and that the Th1 cytokines are increased in postmenopausal women. However, the Th1 immune response is also surprisingly stronger in women, hence affording them a better protection against infections. Nickel sensitivity, a Th1 immune reaction, seems to be more common in women even if men wear earrings. Further, not only the Th2 but also the Th1 autoimmune diseases are generally more common in women than men. How do women advance a stronger Th1 response than men? It is suggested that in contrast to the paradigm that estrogens lead to a Th2 bias, estrogens can enhance Th1 cytokine production also. However, the discrepant effects of estrogens are difficult to be reconciled from a molecular viewpoint and hence are not advocated by all authors. This paper provides an explanation: The effects of dehydroepiandrosterone on Th1/Th2 balance seem to be model-specific; in humans dehydroepiandrosterone, represents a pivotal up-regulator of Th1 immune response. Steroid sulphatase is a microsomal enzyme that cleaves the sulphate group of dehydroepiandrosterone sulphate. This enzyme is controlled by an X-linked gene that escapes the Lyon effect of X-inactivation; as a result, women usually have about twice steroid sulphatase in their cells, including macrophages, as have men. Putting all these facts together, it could be concluded that women's macrophages, which contain higher steroid sulphatase levels and enter peripheral lymphoid organs through afferent lymphatic drainage, produce higher levels of dehydroepiandrosterone in these organs; and higher levels of this hormone produce stronger Th1 immune responses.