Foxp3-expressing regulatory T cells (Tregs) reside in tissues where they control inflammation and mediate tissue-specific functions. The skin of mice and humans contain a large number of Tregs; however, the mechanisms of how these cells function in skin remain largely unknown. Here, we show that Tregs facilitate cutaneous wound healing. Highly activated Tregs accumulated in skin early after wounding and specific ablation of these cells resulted in delayed wound re-epithelialization and kinetics of wound closure. Tregs in wounded skin attenuated IFNγ production and pro-inflammatory macrophage accumulation. Upon wounding, Tregs induce expression of the epidermal growth factor receptor (EGFR). Lineage-specific deletion of EGFR in Tregs resulted in reduced Treg accumulation and activation in wounded skin, delayed wound closure and increased pro-inflammatory macrophage accumulation. Taken together, our results reveal a novel role for Tregs in facilitating skin wound repair and suggest that Tregs utilize the EGFR pathway to mediate these effects.

as palmitic acid, palmitoleic acid and stearic acid, and unsaturated fatty acids, such as oleic acid induced HMel differentiation in vitro and a-MSH increases SZ95 sebocytes intra-Ca 2+ level, which could be an additional indirect mechanism of action on HMel (22,23). In contrast to proliferation studies, high Ca 2+ SZ95 sebocytes resulted in a significant decrease in melanin when compared with low Ca 2+ SZ95 sebocytes, possibly because of pigment dilution and or excessive consumption of melanin precursors by proliferating cells. As previously mentioned, HK extracellular matrix proteins induced HMel proliferation without effect on melanisation; and so could be SZ95 sebocytes in high Ca 2+ level cultures (21). It is also possible that the absence of serum and other supplements may be responsible for these results. Although further studies are needed to clearly define sebocytederived HMel growth factor(s) and their effects on melanin synthesis, the present study denotes that sebocytes exert major paracrine effects on epidermal HMel, which may contribute to constitutive and facultative skin colour. AcknowledgementsPlease refer to Data S1 Acknowledgements. Conflicts of InterestsThe authors have declared no conflicting interests. Supporting informationAdditional Supporting Information may be found in the online version of this article: Data S1. Methods. Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Abstract: Antibodies, specific to murine DEC205, can be used to target antigens to dendritic cells. The immunodominant domain of human type XVII collagen, hNC16A, was fused to this antibody (DEC-hNC16A) and was administered as expression plasmid by gene gun transfection with the aim of inducing tolerance to human type XVII collagen in a skin transplantation model. Mice transfected with DEC-hNC16A were challenged with skin grafts from transgenic mice engineered to express human type XVII collagen. Graft survival was either prolonged or grafts were accepted infinitely (33% and 16%, respectively) upon treatment with DEC-hNC16A while 100% of grafts were rejected in untreated controls. Graft acceptance was associated 395with the absence of a CD4+ infiltrate and a dense CD8+ T-cell infiltrate and was not strictly dependent on antibody production. Our results show that DEC-hNC16A targets dendritic cells in vivo leading to prolonged survival of transgenic skin grafts. This indicates that DEC205-targeting may be used for the induction of tolerance to skin antigens, which would increase the chances of successful skin gene therapy of epidermolysis bullosa patients.

Immune recognition and rejection of tissues expressing transfected genes is a major complication of gene replacement therapy for inherited genetic disorders. Owing to the high immunogenicity of human bullous pemphigoid antigen 2 (hBPAG2), the induction and maintenance of tolerance to this neo-antigen is essential to deliver the gene product to patients with epidermolysis bullosa junctionalis. In a skin grafting mouse model, we used gene gun transfection with a construct encoding hNC16A, the immunodominant domain of hBPAG2, to induce antigen-specific immune tolerance. Eighty percent of wild-type mice transfected with hNC16A showed long-term survival of skin grafts expressing hBPAG2. Tolerance was stable and transferable by T cells but not by B cells of tolerant mice to naive hosts. A dense Foxp3(+) regulatory T-cell (T(reg)) infiltrate was noticed in grafts of tolerant mice and depletion of these cells resulted in a loss of tolerance. Taken together, we show that long-lasting hBPAG2-specific tolerance was induced with gene gun delivery of hNC16A through a T(reg)-dependent mechanism. This is of relevance to patients undergoing gene therapy and has broader implications for the treatment of antigen-specific autoimmune diseases.