Loss of Treg Dnmt1 expression leads to increased activation of T and B cells. (A) Total mononuclear cell counts of peripheral LN and spleens isolated from Dnmt1^−/− versus WT mice (mean ± SD, n = 4 per group). (B) Flow cytometry showing increased expression of T-cell activation markers using CD4+CD25– YFP-Foxp3– Tcon cells isolated from mice with conditional targeting of Dnmt1 in their Tregs versus WT mice. (C) Effects of PMA/ionomycin activation (4 hours) of these cells showing increased cytokine expression by T cells from Dnmt1^−/− versus WT mice. (D) Increased immunoglobulin levels in the sera of Dnmt1^−/− versus WT mice (mean ± SD, n = 4 per group). (E) Increased B-cell activation and class switching in Dnmt1^−/− versus WT mice; proportion of labeled cells is shown in each plot and data are representative of 4 mice analyzed.