The cause of Sjögren's<unk>  is unknown, but it may be the influence of a combination of genetic, environmental, and other factors, as is the case with many other autoimmune disorders. Around 20 autoantibodies could be involved. Genetics The observation of high rates of autoimmune disorders in families with a history of Sjögren's<unk>  is linked with a genetic predisposition to the<unk> . Studies on the polymorphisms of human leukocyte antigen (HLA)-DR and HLA-DQ gene regions in Sjögren's patients show differential susceptibility to the<unk>  as the result of different types of the resulting autoantibody production. Hormones Since Sjögren's<unk>  is associated with a high prevalence in women, sex hormones, especially estrogen, are believed to affect humoral and cell-mediated immune responses affecting susceptibility to the<unk> . Androgens are generally considered to prevent autoimmunity. Studies on mice models suggest estrogen deficiency stimulates presentation of autoantigens, inducing Sjögren's-like symptoms. Microchimerism Microchimerism of fetal cells (offspring lymphoid cells in maternal circulation) may generate autoimmunity in women who have previously been pregnant. Generation of an autoimmune potential via microchimerism may lead to a switch from a silent form of autoimmunity with age-dependent decrease in self-tolerance. Environment Viral proteins, engulfed molecules, or degraded self-structures may initiate autoimmunity by molecular mimicry and increase the chances of Sjögren's<unk>  development. Epstein–Barr virus, hepatitis C, and human T-cell leukemia virus-1 are among the most studied infectious agents in Sjögren's<unk> . To date, no direct causes and effect relationship has been identified between these pathogens and the development of Sjögren's<unk> . Damaged self-structures targeted for apoptosis may be mistakenly exposed to the immune system, triggering autoimmunity in exocrine glands, which are often prone to autoimmune responses.
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