Research ArticlePsoriasis

IL-29 Is Produced by TH17 Cells and Mediates the Cutaneous Antiviral Competence in Psoriasis

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Science Translational Medicine  25 Sep 2013:
Vol. 5, Issue 204, pp. 204ra129
DOI: 10.1126/scitranslmed.3006245

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IL-29 Jumps Out of the Skin

The skin is the first line of defense against infection. It serves not only as a physical barrier but also, when that barrier is broken, as a battleground for the immune system. But what happens during chronic skin diseases, such as psoriasis and atopic dermatitis (AD)? Although patients with both diseases have continuous impaired skin barrier function, only AD patients frequently suffer from cutaneous viral infection. Wolk et al. now report that psoriatic patients are protected by elevated antiviral proteins (AVPs) that are up-regulated in response to interleukin-29 (IL-29) produced by the adaptive immune system.

The authors first compared lesions from AD and psoriatic patients and healthy controls. They found higher amounts of AVPs in the psoriatic lesions. They then compared expression of 30 different cytokines with AVP expression and found that only IL-29 correlated with AVPs. Notably, IL-29 was absent in healthy and AD subjects. Neutralization of IL-29 in psoriatic lesions reduced their AVP expression. The relationship between IL-29 and AVP production was direct because this cytokine increased AVP (but not antibacterial protein) production in multiple models both in vitro and in vivo. What’s more, the IL-29 was secreted by TH17 cells—a proinflammatory immune cell type not previously known to produce IL-29. Together, these results suggest that TH17 cell secretion of IL-29 in psoriatic, but not AD, patients is critical for AVP-mediated viral defense.

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