Autoimmune diseases occur when the immune system becomes too active and mistakenly attacks the body’s own tissues. Typically, the immune system produces antibodies to protect our bodies from harmful things like viruses and toxins. However, in autoimmune disorders, it can’t tell the difference between harmful invaders and healthy cells. There are over 100 types of autoimmune diseases. The exact causes or triggers are not fully understood. Treatments generally aim to reduce the activity of the immune system.