Effects of IRX4204 in acute GVHD depends on pTreg generation. (A-C) Lethally irradiated BALB/c recipients were infused with 10⁷ B6 NTCD BM cells and 1 × 10⁶ flow cytometry–sorted GFP⁻ T cells from B6 Foxp3 GFP KI mice. Recipients were injected with either vehicle or IRX4204 IP daily. The frequency of GFP⁺ T cells (pTregs) was determined in recipient spleens (SPL; A), MLNs (B), and SI (C) 2 weeks after transplantation. (D) Representative flow cytometry plots showing Foxp3 expression in donor CD4⁺ cells from GVHD mouse SPL), MLN, and SI, treated with either vehicle or IRX4204. (E-F) Lethally irradiated BALB/c recipients were infused with 10⁷ B6 NTCD BM cells and 1 × 10⁶ purified B6 scurfy or WT CD25⁻ T cells isolated from scurfy chimeras and WT mice, respectively. Recipients were injected daily IP with either vehicle or IRX4204. Survival plots, weights, and clinical scores of scurfy (E) and WT (F) are shown. One experiment was performed in n = 5-6 per group. *P < .05; **P < .01.