BACKGROUND: The sexually dimorphic prevalence of autoimmune disease remains one 
of the most intriguing clinical observations among this group of disorders. 
While sex hormones have long been recognized for their roles in reproductive 
functions, within the past 2 decades scientists have found that sex hormones are 
integral signaling modulators of the mammalian immune system. Sex hormones have 
definitive roles in lymphocyte maturation, activation, and synthesis of 
antibodies and cytokines. Sex hormone expression is altered among patients with 
autoimmune disease, and this variation of expression contributes to immune 
dysregulation.
OBSERVATIONS: English-language literature from the last 10 years was reviewed to 
examine the relationship between sex hormones and the function of the mammalian 
immune system. Approximately 50 publications were included in this review, and 
the majority were controlled trials with investigator blinding that compared 
both male and female diseased and normal subjects. The review provided basic 
knowledge regarding the broad impact of sex hormones on the immune system and 
how abnormal sex hormone expression contributes to the development and 
maintenance of autoimmune phenomena, with a focus on systemic lupus 
erythematosus, as models of "lupus-prone" mice are readily available.
CONCLUSIONS: Sex hormones affect the function of the mammalian immune system, 
and sex hormone expression is different in patients with systemic lupus 
erythematosus than in healthy subjects. Sex hormones play a role in the genesis 
of autoimmunity. Future research may provide a therapeutic approach that is 
capable of altering disease pathogenesis, rather than targeting disease 
sequelae.