Mice were treated with diphtheria toxin (DT; 3–4 ng/g weight) on day 9, 11 and 13, or with anti-PDCA-1 (20 ng/g weight) 3 times per week beginning on day 8. (A) Kaplan-Meier survival plots. (B) Hemoglobin levels (g/dL) were measured from peripheral blood on day 18. (C) RBCs were stained with anti-mouse IgM-FITC and analyzed by flow cytometry to detect bound anti-RBC antibodies. (D/E) Surface expression of CD69 on CD4+ splenocytes from 15-day-old mice treated with DT (D) or anti-PDCA-1 (E) was analyzed by flow cytometry, or splenocytes were stimulated with 70 ng/ml PMA and 700 ng/ml ionomycin for 5 hours, and IFNγ production by CD4+ T cells was measured by intracellular cytokine staining. Data in A, B, C are from at least four individual mice and four experiments. Each dot in B and C represents one mouse; horizontal bars indicate the mean. Representative FACS data in D and E are from 3 individual mice and three experiments. Calculated statistics are relative to IL-2-KO; *, p<0.05; **, p<0.01; ***, p<0.001.