Biologists in Sweden and the United States associate the unusually frequent development of many autoimmune diseases in women with the activity of the Xist gene, which is responsible for "turning off" one of the two female X chromosomes in their cells. The entry of molecules encoded by this segment of DNA into the blood causes a strong autoimmune reaction, reports the press service of the Stanford School of Medicine.

Previously, all experiments were performed on standard cultures of male cells that do not produce Xist molecules and related proteins and DNA strands. That's why we didn't know about the existence of antibodies to Xist complexes, which are one of the main drivers of the development of autoimmune diseases in women, says Professor Howard Chang of Stanford University.

There are many serious diseases such as lupus and type 1 diabetes, the development of which is due to a malfunction of the immune system, as a result of which its cells attack various organs and tissues of the human body. These autoimmune diseases occur several times more often in women than in men, the causes of which are now being actively studied by biologists and doctors.

Researchers have discovered that one reason is that female cells produce large amounts of RNA molecules that are responsible for "turning off" one of the two X chromosomes. A key role in this process is played by the Xist gene, which is responsible for the production of a special long RNA molecule that binds to the inactivated X chromosome and prevents the cell from “reading” the genes located on it.

Recently, biologists discovered that certain proteins that bind to this RNA molecule and help it suppress the X chromosome can trigger a strong immune response. This led the scientists to study how the mammalian immune system responds to the RNA molecules encoded by Xist, and to examine patient blood samples for antibodies to these compounds.

Experiments have shown that this strand of RNA and associated proteins induce the development of a lupus analogue in both female and male mice, resulting in extensive organ damage. Also, the researchers found antibodies against these biomolecules in blood samples from more than 100 patients with lupus, scleroderma and Wagner's disease.

All this indicates that the Xist gene largely determines women's high susceptibility to autoimmune diseases, the scientists concluded.