It’s long been a scientific mystery why women suffer more from auto-immune diseases than men.
And it’s not by a just a little bit. It’s estimated four out of five people suffering from auto-immune diseases are women.
Auto-immune diseases include rheumatoid arthritis, type 1 diabetes, multiple sclerosis, inflammatory bowel disease and psoriasis. And quite often if you have one of these conditions, you are at risk of being diagnosed with others.
However a cluster of recent studies may have solved the issue of why women are more at risk, and it appears it’s all down to that X chromosome.
So what are auto-immune diseases?
Auto-immune disorders occur when a person’s immune system mistakenly attacks their body. There are about 80 different autoimmune disorders with varying severity, from mild irritation to complete disability. There are no cures, but the symptoms can be treated, as with insulin and diabetes. About one in 10 people suffer from an auto-immune disease.
As mentioned, women suffer disproportionally, which has attracted a great deal of research which is now paying off.
It turns out the X chromosome is playing up, and as women have two of these, it doubles their chances.
A Stanford study describes the problem as having “too much of a good thing” with two X chromosomes. There is also a lot more genetic information on the X chromosome, which is where the problem starts. The Y-chromosome contains just about a hundred genes, but the X-chromosome contains more than 900.
“Having two X chromosomes risks the production, in every female cell, of twice the amount of the myriad proteins specified by the X but not the Y chromosome. Such massive overproduction of so many proteins would be lethal,” the study stated.
Nature overcomes this by shutting down production of the proteins in one of the X chromosomes. That way, the same amount of each X-chromosome-specified protein is produced in a female cell as in a male cell.
According to National Geographic, the Standford study shows that a molecule called Xist (pronounced ‘exist’), which turns off one copy of the X-chromosome in every cell in the female body, can trigger a rogue immune response. Another study from France, not yet peer-reviewed, shows that when certain genes on the silenced X-chromosome become active again, it can cause lupus-like symptoms in older mice.
Not about hormones
Previously, it was thought that as diagnosis were overwhelmingly for female patients that it was somehow linked to sex hormones.
“Our study shows that you do not need female sex hormones; you don’t even need a second X-chromosome; just this Xist [molecule] could have a major role in developing some autoimmune diseases,” says Howard Chang, a dermatologist and molecular geneticist at Stanford University School of Medicine in California, who led the study.
“There is clear evidence now that the sex bias in autoimmune disease is not only linked to hormones but also to the presence of the number of X chromosomes and to the process of X chromosome inactivation,” says Claire Rougeulle, an epigeneticist who led the second study at the National Centre for Scientific Research (CNRS) in the Université Paris Cité in France.
According to National Geographic, Chang has been studying the Xist molecule for many years and in 2015 he discovered that many proteins working together with Xist were involved in autoimmune disorders and were attacked by rogue antibodies, called autoantibodies. Instead of fighting foreign invaders, such as germs, autoantibodies mistakenly target an individual’s own cells.
This enthusiasm for the X chromosome to ‘fight’ things in our bodies may even have an evolutionary purpose. It’s been proposed women have much more ability to produce antibodies to fight diseases as a result of being required to protect their children.
How does this help?
Close examination of blood samples from about 100 patients with autoimmunity showed the presence of autoantibodies in many of the complexes associated with Xist.
While some autoantibodies were specific to certain autoimmune diseases, others were common among several. So, it might be possible to develop a panel of autoantibodies that could be used to distinguish between different disorders. However, the study noted that any such treatment was a long way off.
Do you suffer from an auto-immune disease? How has it affected your life? Why not share your experience in the comments section below?
Also read: Foods that help psoriasis
