IL17A and inflammatory bowel disease: The in-depth study of the pathogenesis and treatments of PsA has allowed us to understand that dysregulation of the IL-23/IL-17 axis can greatly facilitate the induction of chronic inflammation and autoimmunity, and contribute to various autoimmune diseases such as PsA, psoriasis, ankylosing spondylitis, rheumatoid arthritis, inflammatory bowel disease, etc. [26–29].