Emerging role of IL-17 and Th17 cells in systemic lupus erythematosus

• High levels of IL-17 are found in serum and injured tissues during SLE.
• IL-17 sources include both T lymphocytes and innate cells.
• Immune complexes-induced inflammation sustain IL-17 production during SLE.
• Several T cell intrinsic alterations skew their cytokine production toward IL-17.
• IL-17 exerts a major role in auto-antibody production and organ damage in SLE models.

Despite the success of targeted therapies in managing immune-mediated inflammatory diseases (IMIDs) such as RA, IBDs, MS and psoriasis, unmet needs for such approach in SLE are widely recognized. In the past 2 years, exciting insights supporting previous lines of evidence on the role of the IL-23/IL-17 axis in SLE have emerged. This is of particular importance as IL-17 blockers have now moved successfully into the clinical space, as illustrated in psoriasis and ankylosing spondylitis. However, recent fundamental studies also highlighted unexpected aspects of IL-17/Th17 biology whose comprehension may prevent disappointing results of IL-17 targeting such as those obtained in Crohn's disease. Therefore, establishing a current picture of the IL-17 pre-clinical situation in SLE is timely in order to plan future proof-of-concept studies in human.