IRX4204 amelioration of acute GVHD is associated with reduced donor T-cell expansion and Th1 differentiation. (A-B) Lethally irradiated BALB/c recipients were infused with 10⁷ B6 NTCD BM cells and 8.5 × 10⁶ CFSE-labeled purified B6 T cells. Recipients were treated IP daily with either vehicle or IRX4204. Mice were euthanized on day 6 after transplantation to determine proliferation capacity (A) and responder frequency (B). (C-F) Lethally irradiated BALB/c recipients were infused with 10⁷ B6 NTCD BM cells and 5 × 10⁶ B6 splenocytes, with or without daily IP injections of IRX4204. The frequency of donor T cells expressing IFN-γ and TNF-α (C), IL-17 (D), and IL-4 (E) from spleen on day 7 and LI LPLs (F) on day 21 after transplantation was determined by intracellular staining. *P < .05; **P < .01; ***P < .001; ****P < .0001.