Isolation of pDCs and cDCs. B cells (CD11c⁻ B220⁺), pDCs (CD11c^int B220⁺), and cDCs (CD11c^high B220⁻) were isolated from the spleen or BM of FL-treated mice. (A) Two-dimensional counter plots of B220 and CD11c staining. Percentages of cells are shown enclosed in circles. (B) Cell morphology stained with May-Giemsa (magnification ×400). (C) Immunophenotyping. Filled histograms; pDCs, broken-lined open histograms; pDCs stained with isotype controls, solid-lined open histograms for Ly6C, mPDCA-1, CD86, I-A^b, and CD11b; cDCs, those for CD19 and CD49b; B cells and enriched CD49b⁺ cells as positive controls, respectively. (D) Production of IFN-α (top) and IL-12p70 (bottom) after incubation of cells with CpG 2216 for 16 hours (mean ± SD). (E,F) Aliquots of 2 × 10⁵ BALB/c CD4⁺ T cells were cultured with 10⁴ cells from each APC subset isolated from FL-treated (E) and FL-untreated mice (F), with or without 1 μM CpG 1668, and their proliferation 3 days later was shown as mean plus or minus SD. N.D. indicates not done. Data are representative of at least 2 similar experiments. *P < .05 compared with B cells.