Antagomir-treated tTregs decrease mortality in a xenogeneic model of GVHD. Naive PB tTregs were sort-purified, expanded in vitro, and either left untreated or incubated with scramble RNA or miR-146b antagomir for 2 days. Following treatment, tTregs were washed and cotransferred (15 × 10⁶) with allogeneic PBMCs (15 × 10⁶) into NOD/Scid/γc^−/− mice to assess the ability to ameliorate xenogeneic GVHD. n = 10, 10, 9 and 10 for the PBMC, untreated, scramble-treated, and antagomir-treated groups, respectively. (A) Kaplan-Meier survival curves for mice receiving PBMCs ± groups of tTregs. *P < .05. (B) Average weight (percentage of initial) for mice surviving on a given day for different groups of mice (*P < .05 for all tTreg groups from days 15 to 22). (C) Average GVHD score for mice surviving on a given day for different groups of mice. *P < .05 for all tTreg groups from days 13 to 22. GVHD severity was measured by enumerating PBMC-derived (ie, HLA-A2⁺) T-cell numbers in circulation on day 14 in the (D) HLA-A2⁺ total, (E) CD4⁺ HLA-A2⁺, and (F) CD8⁺ HLA-A2⁺ populations, respectively. (G) In vivo tTreg persistence was determined by enumerating CD4⁺ HLA-A2⁻ cells in the blood on day 7. (H) The FoxP3⁺ tTreg population was maintained in all groups. Data shown are representative of 2 independent xenogeneic GVHD experiments.