Regulatory T cells preserve alloengraftment in model of late-gestation IUHCT in immunocompetent recipients. (A) Newborn Balb/c pups were injected at 20 DPC with TCD BM harvested from B6^GFP mice in combination with regulatory T cells harvested from either chimeric or naive donor mice, as displayed. As maternal sensitization only occurs with prenatal injection, pups injected postnatally were not fostered. (B) Frequency of macroengraftment defined as the number of pups with PB chimerism higher than 1% at 4 weeks of age divided by the total number of injected pups in that group. Data were analyzed using Fischer’s exact test. (C) Mean PB chimerism among macroengrafters over time. Shown are the mean ± standard error of the mean. Data were analyzed using ANOVA. (D) Lineage frequency among donor-derived (GFP⁺) cells in the PB at 6 months of age. Mean and standard deviation are included in addition to individual data points. Data were analyzed using ANOVA. (E) In vivo mixed lymphocyte reaction performed at 6 months of age. Percentage proliferating was defined as the percentage of H2k^b-GFP⁻CD3⁺ cells with APC fluorescence intensity of 50% or less of undivided cells. Mean and standard deviation are included in addition to individual data points. Data were analyzed using ANOVA. In all panels, statistically significant differences between groups are indicated by * (P < .05).