Autoimmunity is where the immune system recognises a self antigen and starts attacking its own cells and organs. There are many diseases which are autoimmune in origin such as Type 1 diabetes, Rheumatoid Arthritis and Graves disease. Crohn's disease is NOT an immune disease as no self antigen has ever been found and this is supported by many gastroenterologists, it's more likely that Crohn's is some sort of infectious agent.