The IL-20 cytokines IL-19, IL-20, IL-22, IL-24, and IL-26 are elevated in autoimmune/inflammatory diseases, such as in the skin of patients with psoriasis (18, 33, 34), in synovial fibroblasts, and macrophages of patients with rheumatoid arthritis (19, 35) and in patients with inflammatory bowel disease (20, 27, 30, 36–39). Here, IL26 is linked to inflammatory bowel disease.