<human>:  Why do some people develop autoimmune diseases?
<bot>: Autoimmunity is a condition in which the immune system attacks the body’s own cells. The most common autoimmune diseases are rheumatoid arthritis, multiple sclerosis, and lupus. Autoimmune diseases are caused by a combination of genetic and environmental factors. Some people are born with a genetic predisposition to develop autoimmune diseases, while others develop them after exposure to certain environmental triggers.