The immune system is the body’s defense system. When healthy, it protects the body by making antibodies (blood proteins) that attack foreign germs and cancers. With lupus, the immune system misfires. Instead of producing protective antibodies, an autoimmune disease begins and makes “autoantibodies,” which attack the patient’s own tissues. Doctors sometimes refer to this as a “loss of self-tolerance.”
As the attack goes on, other immune cells join the fight. This leads to inflammation and abnormal blood vessels (vasculitis). These antibodies then end up in cells in organs, where they damage those tissues.
Why this inflammatory response begins is not clear. It most likely results from a mix of inherited tendencies and things in your environment. These include viruses, sunlight and drug allergies. People with lupus may also have an impaired process for clearing old and damaged cells from the body, which causes an abnormal immune response.