TH17 Cells Are Critical for Skin-Specific Pathological Injury in Acute Graft-Versus-Host Disease

Interleukin-17 (IL-17), which is important for host defens, has been implicated in autoimmune and chronic inflammatory diseases. As knockout mice lack IL-17 expression in δγT, NKT-like cells, studies investigating the association between TH17 cells and cutaneous graft-versus-host disease (GVHD) in animal models have reported conflicting results. To determine the role of TH17 cells in cutaneous GVHD, we developed an acute GVHD model using C57BL/6(H-2b) donors to BABL/c (H-2d) recipients. Blood samples and skin were examined for inflammation and infiltrating cells using histology and fluorescence-activated cell sorter (FACS) on days 6 and 15 after bone marrow transplantation. We found donor T cells to mediate severe cutaneous inflammation, which was ameliorater by administration of halofuginone (HF) to the recipients. Mechanistically, we demonstrate the severe tissue damage during this disorder to be associated with the production of IL-17 and the expansion of IL-17-producing CD4+ cells. Specific inhibition of TH17 differentiation and function by HF reduced disease severity. Thus, TH17 cells are sufficient to induce acute cutaneous GVHD.