PDCs enhance plasma cell development and immunoglobulin production of antigen- and CpG-stimulated B cells. B cells (1 × 10⁵ B cells/200 μL/well) were incubated alone or in the presence of PDCs (1 × 10⁴ PDCs/200 μL/well) and were stimulated with CpG-C (3 μg/mL), anti-Ig (10 μg/mL), or a combination of CpG-C and anti-Ig. (A) After 8 days the frequency of plasma cells (CD20^-CD38⁺) was determined by flow cytometry. The frequency of CD20^-CD38⁺ plasma cells is indicated in the upper left quadrant (top panel, B cells alone; bottom panel, B cells cocultured with PDCs). One representative dot plot is shown. (B) The mean plasma cell frequencies (± SEM) of 5 independent experiments are depicted. (C) After 13 days IgM (left panel) and IgG (right panel) were measured in the supernatants by ELISA. Data are shown as means ± SEM of 3 independent experiments (□, B cells alone; ▪, B cells plus PDCs).