Can you tell me what autoimmune diseases are?

Body attacks itself: Autoimmunity is when the infection-fighting system turns against the body. Examples include many cases of hypothyroidism, some joint problems (rheumatoid arthritis, lupus), ms, psorias and inflammatory bowel disease (eg, crohn's).

Autoimmune disease: Autoimmune disease is simply the bodies own immune system, especially the antibodies, somehow act foolish and start to recognize our own 'self' proteins as foreign and end up attacking them. Kind of a deranged immune system.