Staphylococcus aureus Epicutaneous Exposure Drives Skin Inflammation via IL-36-Mediated T Cell Responses

Staphylococcus aureus colonization contributes to skin inflammation in diseases such as atopic dermatitis, but the signaling pathways involved are unclear. Herein, epicutaneous S. aureus exposure to mouse skin promoted MyD88-dependent skin inflammation initiated by IL-36, but not IL-1 alpha/beta, IL-18, or IL-33. By contrast, an intradermal S. aureus challenge promoted MyD88-dependent host defense initiated by IL-1 beta rather than IL-36, suggesting that different IL-1 cytokines trigger MyD88 signaling depending on the anatomical depth of S. aureus cutaneous exposure. The bacterial virulence factor PSM alpha, but not alpha-toxin or delta-toxin, contributed to the skin inflammation, which was driven by IL-17-producing gamma delta and CD4(+) T cells via direct IL-36R signaling in the T cells. Finally, adoptive transfer of IL-36R-expressing T cells to IL-36R-deficient mice was sufficient for mediating S. aureus-induced skin inflammation. Together, this study defines a previously unknown pathway by which S. aureus epicutaneous exposure promotes skin inflammation involving IL-36R/MyD88-dependent IL-17 T cell responses.