T reg cell–specific Drosha or Dicer deficiency recapitulates the scurfy phenotype. (A) Kaplan-Meyer survival plot of Drosha^F/Δ Foxp3^Cre/Cre(Y), Dicer^F/F Foxp3^Cre/Cre(Y), and control mice (Drosha^F/+ Foxp3^Cre/Cre(Y), Drosha^F/Δ Foxp3^Cre/+, Drosha^F/+ Foxp3^Cre/+, Dicer^F/+ Foxp3^Cre/Cre(Y), and Dicer^F/+ Foxp3^Cre/+). (B) Massive lymphadenopathy in a female Drosha^F/Δ Foxp3^Cre/Cre mouse. Shown are the cervical lymph nodes. (C) Cell counts of lymphoid organs from moribund Drosha^F/Δ Foxp3^Cre/Cre or Drosha^F/Δ Foxp3^Cre/Y mice and littermate controls. Data represent the mean ± SD of four mice at 2.5–3 wk of age. (D) Only marginal changes in the proportions of B (CD19⁺), γδT (TCRγδ⁺), myeloid (CD11b⁺), and T cells (TCRβ⁺) in the spleen and lymph nodes of Drosha^F/Δ Foxp3^Cre/Cre mice. (E) Aberrant T cell activation in the spleen and lymph nodes of moribund Drosha^F/Δ Foxp3^Cre/Cre mice. (F and G) Cytokine expression by CD8⁺ (F) and CD4⁺ (G) T cells from Drosha^F/Δ Foxp3^Cre/Cre mice. (H and I) Foxp3 expression in total splenocytes (H) and CD4⁺ T cells (I). Percentages of cells are shown in D–I. (J) H&E-stained sections of the lung (i and iii) and liver (ii and iv). Designation of Foxp3^Cre/Cre(Y) alleles indicates that both males and females were included in the experiments. Bars, 100 μm.