It has been reported that large numbers of TH17 cells and high levels of serum IL-17 are found in many autoimmune diseases, including multiple sclerosis (MS), inflammatory bowel diseases, rheumatoid arthritis, Lyme disease, contact dermatitis, psoriasis, uveitis, and experimental autoimmune encephalomyelitis (EAE) [12–14]. Here, IL17A is linked to inflammatory bowel disease.