Autoimmune disease is a broad category of related diseases in which a person’s immune system mistakenly attacks the tissues and organs it was designed to protect. Normally, the body’s immune system protects it by responding to invading microorganisms, such as bacteria and viruses. The immune system produces antibodies, which are special proteins that recognize and destroy the invaders. Autoimmune diseases occur when these autoantibodies attack the body’s own cells, tissues, and organs.
- There are more than 100 autoimmune diseases.