Lupus is an autoimmune disease. This means the body forms antibodies against itself. Normally an antibody attaches itself foreign invaders like bacteria and viruses and tells the immune system to kill it. It’s the body’s way of tagging unwelcome visitors. Think of a laser-guided missile. The laser is the antibody and the missiles are the immune system.
In rheumatoid arthritis, this laser is pointed at the joints, in Ulcerative Colitis the laser is pointed at the gut and in Type 1 Diabetes, the laser is pointed at the insulin-producing cells in the pancreas. Lupus is a little different.