Autoimmune diseases vary greatly, but each causes the immune system to attack healthy tissue.

Autoimmune diseases can affect almost every body part or system. There are more than 80 of these conditions, and some are more common than others.

Common examples include hypothyroidism, type 1 diabetes, rheumatoid arthritis, lupus, and inflammatory bowel disease (IBD).

The immune system is a network of tissues, organs, and cells. Its role is to defend the body against harmful organisms, such as bacteria and viruses, warding off infection and disease.

In a person with an autoimmune disease, the immune system mistakenly attacks healthy body cells and tissues.

Researchers do not know the causes of many autoimmune conditions, but genetic factors, past infections, and environmental factors can affect their development.

Long-term treatments aim to reduce the strength of immune responses. Antibiotics are not involved because these diseases are not bacterial infections.