Targeting IL-17 in inflammatory disease

The interleukin-17 (IL-17) family cytokines are strong inducers of inflammation and help to protect us against invading pathogens. However, they also have a dark side and contribute to the tissue destruction that occurs in chronic inflammatory and autoimmune diseases such as psoriasis, rheumatoid arthritis and multiple sclerosis.

The landmark discovery that IL-17-producing T cells were central drivers of these diseases positioned IL-17 as a promising therapeutic target. Several approaches that disrupt signalling by this cytokine family are now being tested in the clinic. Excitingly, real benefits for patients are starting to emerge, particularly for patients with psoriasis.

This collection of Research and Review-type articles highlights the role of the IL-17 pathway in inflammatory diseases, and how our improved understanding of the mechanisms of disease has revealed new opportunities for and potential benefits of IL-17-targeted therapies.

The content for this collection has been chosen by the editors of Nature Reviews Immunology and selected Comment and Review articles have been made freely available for 6 months, thanks to support from Eli Lilly and Company.

In addition, Nature Reviews Drug Discovery presents a Poster that summarizes the key aspects of the IL-17 pathway relevant to its potential as a therapeutic target, and an Animation of the immunopathology of psoriasis that illustrates how agents that target IL-17 signalling are being developed into novel therapies for this disease and other inflammatory conditions.

In mice, it is possible to induce a psoriasis-like condition by applying imiquimod; here, the production of interleukin-23 that is stimulated by such skin inflammation is shown to depend on the interaction of nociceptors expressing the Nav1.8 and TRPV1 channels with skin-resident dendritic cells.

Letter | | Nature

Regulatory T (Treg) cells exhibit substantial phenotypic and functional plasticity. Hiroshi Takayanagi and his colleagues report that in autoimmune arthritis, a subset of Treg cells can lose Foxp3 expression and convert into TH17 cells. This conversion is mediated by synovial fibroblast-derived IL-6, and in vivo, these cells are osteoclastogenic and exacerbate arthritis. These findings suggest that a proportion of pathogenic TH17 cells in autoimmune disease may be derived from Treg cells.

Article | | Nature Medicine

A global view of the genetic networks regulating the differentiation of TH17 cells is presented, based on temporal expression profiling, computational network reconstruction and validation of predicted interactions by nanowire-mediated siRNA perturbation.

Article | | Nature

Exposure to interleukin 23 (IL-23) is required for the induction of pathogenic TH17 cells. Kuchroo and colleagues show that IL-23-dependent induction of the cytokine TGF-β3 produces a molecular signature characteristic of highly pathogenic TH17 cells.

Article | | Nature Immunology