Induction of B-cell proliferation and Ig secretion by pDCs. Freshly isolated pDCs were stimulated for 24 hours with 1μM CpG-B and then added to B cells cultured over irradiated CD40L-transfected L cells alone or in the presence of IL-2 (50 U/mL), IL-10 (10 ng/mL), or both as indicated. (A) B cells were labeled with CFSE before culture. After 5 days of coculture, cells were harvested and stained with allophycocyanin-labeled anti-CD19 to allow residual pDCs to be excluded, and CFSE dilution was analyzed by flow cytometry. pDC/B-cell coculture experiments: Results are shown in the left panel; shaded histogram represents B cells cultured with CD40L; dashed histogram, B cells cultured with resting pDCs; and solid histogram, B cells cultured with CpG-B-pDCs. Control experiments: Results are shown in the right panel; shaded histogram represents B cells cultured with CD40L; and dotted histogram, B cells cultured with CD40L plus 1μM CpG-B. The results shown, which are representative of at least 5 individual donors, have been gated on the CD19⁺ population. (B) Similar cultures were established with unlabeled B cells; supernatant was collected on day 14, and IgG and IgM concentrations were measured by ELISA. Results shown are representative of 3 independent experiments. The average of duplicate results from 2 individual donors ± SEM is shown. Results were analyzed using unpaired t test: *P < .05, **P < .01, and ***P < .001.