Update on interleukin-17: a role in the pathogenesis of inflammatory arthritis and implication for clinical practice.

Interleukin-17 (IL-17A) is a cytokine critical for the acute defence against extracellular bacterial and fungal infections. Excess production during chronic inflammation has been associated with many inflammatory and autoimmune disorders. The present review describes the key molecules of the IL-17 pathway, which are or could be targeted for treatment. Since targeting of IL-17A may affect defence mechanisms, the pathogenesis of such possible adverse events is analysed. Then the contributions of IL-17 to bone changes in various forms of arthritis are discussed. Finally, the results of current inhibitors of the IL-17 pathway in clinical trials are detailed. IL-17A inhibition has been first registered for the treatment of psoriasis, psoriatic arthritis and ankylosing spondylitis. Other therapeutic options are now tested in a long list of diseases.