Regulation of human dendritic cells by B cells depends on the signals they receive. (A-B) Peripheral blood CD14⁺ monocytes from healthy donors were cultured in the presence of GM-CSF (1000 IU/10⁶ cells) and IL-4 (500 IU/10⁶ cells) alone (Ctrl) or cytokines and BCR-activated (10 μg/mL of F(ab′)₂ anti–human IgM) CD19⁺ B cells (at ratio of 1:4; Mo + B + BCR) or cytokines and BCR + CpG-ODN-2006 (0.25μM; Mo + B + BCR/CpG) for 6 days. (A) Expression of DC surface markers (mean fluorescence intensities [MFI]) as analyzed by flow cytometry on CD20-negative cells (n = 5 experiments). (B) Percentage of annexin V⁺ apoptotic DCs from days 1 to 3 after coculture with B cells (n = 3 experiments). (C) Five-day-old monocyte-derived immature DCs were cultured in the presence of GM-CSF and IL-4 alone (DC Ctrl) or stimulated with LPS (100 ng/mL; DC + LPS) or cocultured at 1:4 ratio with BCR-activated CD19⁺ B cells in the presence of LPS (DC + B + BCR + LPS) for 48 hours to analyze the expression of surface markers (% positive cells and MFI) on CD20-negative cells. (n = 5 experiments). (D) CD19⁺ B cells were either nonstimulated (B-Ctrl) or stimulated with BCR (B-BCR) or BCR + CpG (B-BCR/CpG) for 3 days and expression of surface markers (% positive cells) was analyzed (n = 3 experiments). The statistical significance as determined by 2-tailed paired Student t test is indicated (*P < .05 v/s Ctrl; ^#P < .05 v/s DC + LPS, and **P < .05 vs B-BCR).