Interleukin 17 (IL-17) and its closest relative, interleukin 17-F (IL-17F), are expressed by a distinct type of T cells, T helper 17 cells and certain other lymphocytes. These cytokines play key regulatory roles in hose defence and inflammatory diseases. IL-17 is involved in various autoimmune diseases, including: rheumatoid arthritis, psoriasis, multiple sclerosis and inflammatory bowel disease.

Interleukin-22 (IL-22) has important functions in host defence at mucosal surfaces as well as in tissue repair. It is unique as a cytokine that is produced by immune cells, including T-helper (Th) cell subsets and innate lymphocytes, but acts only on non-haematopoietic stromal cells, in particular epithelial cells, keratinocytes, and hepatocytes. Although IL-22 is beneficial to the host in many infectious and inflammatory disorders, depending on the target tissue it can be pathogenic due to its inherent pro-inflammatory cytokines, in particular, IL-17. IL-22 is involved in various autoimmune and inflammatory conditions, including: inflammatory bowel disease, psoriasis, rheumatoid arthritis, synovial fibroblasts, Crohn’s Disease and ulcerative colitis.

Interleukin-23 (IL-23) is a member of the IL-12 family of cytokines with pro-inflammatory properties. It’s ability to potently enhance the expansion of T helper type 17 (Th17) cells indicates the responsibility for many of the inflammatory autoimmune responses. IL-23 is found in the skin of patients with psoriasis, in the bowel wall of patients with chronic inflammatory bowel disease, and in synovial membrane of patients with rheumatoid arthritis.