Effector CD70⁺ T cells are increased in blood and skin of patients with GVHD. (A) Percentage of CD4⁺CD70⁺ (left) and CD8⁺CD70⁺ (right) cells in patients who underwent allo-HSCT, with ongoing GVHD (n = 12) vs those without aGVHD (no GVHD; n = 12) at matched time points after HSCT. (B) Percentage of IFN-γ⁺ cells within CD4⁺CD70⁺ and CD4⁺CD70^– cells in blood of patients with ongoing aGVHD (n = 6). (C) Percentage of interleukin-17–positive (IL-17⁺) cells within CD4⁺CD70⁺ and CD4⁺CD70^– cells in blood of patients with ongoing aGVHD (n = 6). (D) Percentage of perforin-positive cells within CD4⁺CD70⁺ and CD4⁺CD70^– cells in blood of patients with ongoing aGVHD (n = 6). (E) Percentage of granzyme-B–positive cells within CD4⁺CD70⁺ and CD4⁺CD70^– cells in blood of patients with ongoing aGVHD (n = 6). (F) Immunofluorescence staining on skin, gut, and liver FFPE sections from 4 patients with severe aGVHD after allo-HSCT. Staining was performed with nuclei stain DAPI (blue), CD70-Cy3 (red), and CD3-FITC (green). Images taken at 40× magnification. Arrows indicate presence of double-positive (CD3⁺CD70⁺) T cells. (G-H) Cell surface expression of chemokine receptors CCR4 and CCR6 on total CD4⁺ and CD4⁺CD70⁺ (G), and total CD8⁺ and CD8⁺CD70⁺ T cells (H) in blood (PB) and skin. (I) Serum levels of sCD27 measured at day 14 after SCT in patients who subsequently developed aGVHD (n = 22), compared with patients who never developed aGVHD (n = 11). (J) Serum sCD27 measured in patients at onset of GVHD (n = 25), compared with patients who never developed aGVHD (n = 15) at matched time points after HSCT. Statistical comparisons were made using Wilcoxon matched-pairs signed-rank test (A-E,G): ∗P < .05; ∗∗P < .01; ∗∗∗P < .005. FITC, Fluorescein isothiocyanate.