[Focusing on tissue biomarkers. Estrogens as key players in the immune response and autoimmunity]

Estrogens modulate the immune response as well as the risk and progression of autoimmune disorders. Their effects are mediated by nuclear receptors (i.e. estrogen receptor alpha and beta), membrane receptors, and are influenced by their interactions with other hormones. Locally produced hormones and cytokines are the main factors in maintaining tissue homeostasis. The response of immune cells to estrogens is related to their developmental stage. The diverse effects of estrogens on various autoimmune disorders are the result of the versatility of their pathomechanism. In general, progression of B-cell mediated disorders is aggravated by estrogens. Their effects on T-cell mediated disorders, on the other hand, are driven by Th1 or Th2 dominance. As estrogens promote the escalation of the Th2 immune response, Th2-dominant disorders are aggravated, while Th1-dominant disorders are ameliorated upon high estrogen levels. Inflammation on its own also modulates the impact of estrogens. Inflammatory cytokines alter the expression of the alpha and beta estrogen receptors as well as the activity of estrogen metabolizing enzymes. Monitoring the local, tissue-wide interaction between hormones and immune cells would provide a better tool for identification and characterization of molecules involved in this system. To date, routinely used laboratory methods have a limited role in monitoring the local effects of estrogens. In this current paper the authors summarize the role of estrogens in immune system and overview those novel methods which are useful in the investigation of local endocrine milieu.