Autoimmunity in women: an eX_amination of eX_isting models

Women comprise over 80% of the affected individuals for many autoimmune conditions. Although sex-specific differences in sex hormones are thought to contribute to the female predisposition to autoimmunity, emerging evidence also suggests an intriguing role of both physiological and dysregulated X-chromosome inactivation. Furthermore, recent studies have demonstrated that many immune genes encoded on the X chromosome are expressed biallelically, and the contribution of these sex-specific differences in immune gene dosage to autoimmunity remains to be fully explored. This review highlights recent developments in this field and discusses questions that remain unanswered.