What causes a person to have an autoimmune disease?
Many answers, unfortunately most unknown. Genetics play a major role; there are mouse strains in which every single female gets lupus. Sex does; for most autoimmunities, females are at higher risk. Harmful cross-reactions seem to be involved, too; the antibodies that some people make against certain Streptococci turn around and react against their heart. And sometimes, tissues are damaged as innocent bystanders while the immune system is fighting an infection; recently this have been proposed as a cause of Crohn Disease.
