Tregs impact multiple phases of GvHD. (A) Survival is shown for Balb/c hosts that received Tregs at various time points at or after transplantation of Tcons (cell ratio of 1:1) and TCD-BMs on day 0 (P < .001 for Tcons vs Tcons + Tregs on d2, d6, d9, or d14; P < .05 for Tcons vs Tcons + Tregs on d21; n ≥ 7). Data are combined from 2 independent experiments. (B) Survival of animals that received donor Tcons on day 0 for GvHD induction and Tregs on day 0 (•, n = 7) versus day 21 (▪, n = 6) at cell ratio of 0.5:1 with Tcons (P < .001). Survival data showed protection by Tregs is dose dependent at later phases of GvHD. Data are combined from 2 independent experiments.