IL17A and inflammatory bowel disease: The main cytokine in IBD patients is interleukin-1α (IL-1α); interleukin-1β (IL-1β); interleukin-2 (IL-2); interleukin-6 (IL-6); interleukin-8 (IL-8); interleukin-12 (IL-12); interleukin-17 (IL-17); interleukin-23 (IL-23); tumour necrosis factor (TNF); and interferon (IFN).