The many faces of interleukin-17 in inflammatory skin diseases

Interleukin (IL)-17 is an emerging target for inflammatory skin disorders. Given the remarkable success of its therapeutic inhibition in psoriasis, the pathogenic role of this cytokine is being explored in other immune-mediated diseases. Interestingly, IL-17 is linked to particular skin conditions where its activation coincides with disease flares. The leading hypothesis for its contribution to proinflammatory signalling cascades is driving inflammasome activation. However, IL-17 stimulation also releases a range of noninflammasome-related cytokines from human skin. Furthermore, a role in cytotoxic responses and an important interplay with the microbiome is hypothesized. While treatment failure would be surprising in neutrophilic dermatoses, the picture might be more complex in lymphocyte-mediated conditions. Nonetheless, increasing insights into the pathogenesis suggest that beneficial responses are also probable in the latter conditions. Study of this pathway in the skin reveals some intriguing aspects of the IL-17-related immunological network.