Women get autoimmune disorders such as lupus far more often than men, and a new study suggests the best explanation to date for why that is. It's all about the extra X chromosome that women carry, reports STAT News. More specifically, the study in the journal Cell focuses on a molecule called Xist, pronounced "exist," that is found only in females, per the Washington Post. The molecule plays a crucial role in that it essentially silences that extra X chromosome, "averting what would otherwise be a disastrous overproduction of proteins," explains the Post. But in doing so, Xist might "sometimes confuse the immune system," per the New York Times.
This confusion appears to contribute to the onset of ailments such as lupus or rheumatoid arthritis, with women accounting for a staggering 80% of such autoimmune diseases. (For lupus in particular, it's closer to 90%.) Researchers say this can't be the full explanation given that some men also get the diseases, but "it's a very interesting piece of the puzzle," says David Karp of the UT Southwestern Medical Center in Dallas. Future treatments that zero on the molecule could replace current ones that seek to "blunt the entire immune system," per the Times. "Maybe that's a better strategy," says Stanford's Dr. Howard Chang, who led the new study.
The discovery comes from research on mice, and the next step is try to replicate the findings in humans. Chang says the study suggests that inflammation or tissue damage in women might "expose Xist-protein complexes" and trigger antibodies that raise the risk of an autoimmune disease, per STAT. "What our study really showed was that it's not just the second X chromosome, it's actually a very special RNA (the Xist molecule) that comes from that second X chromosome, and just that RNA perhaps plays a major role." (More autoimmune disease stories.)
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