Development of Dnmt1^−/− versus WT Foxp3+ Tregs. (A) Intranuclear flow cytometric staining for Foxp3 after gating on CD4 T cells, showing accumulation of Foxp3+ cells in thymii of Foxp3cre/Dnmt1^−/− mice, but their diminution in LN and spleen samples compared with normal controls; proportion of labeled cells shown in each plot and data representative of 5 mice per group per time-point. (B) Pooled data (n = 5/ group) for proportions of Foxp3+ Tregs (mean ± SD) in each lymphoid tissue. (C) Compared with WT Tregs, Foxp3cre/Dnmt1^−/− Tregs had increased susceptibility to apoptosis upon overnight TCR stimulation; annexin-V staining. (D) Pooled data to (C) from 3 independent experiments.