Adding back of IL-17 to recipients given IL-17^−/− donor cells ameliorated acute GVHD. (A,B) Recipients given spleen (2.5 × 10⁶) and TCD-BM cells (2.5 × 10⁶) from IL-17^−/− donor cells were injected intraperitoneally with recombinant IL-17 (0.3 μg/mouse) on days 0, 3, and 7 after HCT. Body weight change and survival curves are shown. There were 12 recipients in each group; 3 replicated experiments were combined. (C,D) Histopathology of liver, gut, and lung of recipients treated with PBS or IL-17 13 days after HCT. Arrow points to the necrosis area in liver and infiltrated epithelial and lamina propria areas in gut of recipients given PBS treatment only. One representative of histopathology and mean (± SE) of histology score of 6 examined recipients in each group is shown. (E) Mean (± SE) of the percentage of donor-type IFN-γ⁺CD4⁺ or CD8⁺ T cells in MLN, spleen, and liver of recipients treated with IL-17 or PBS 13 days after HCT. There were 4 recipients in each group.