Characteristic of the intercellular contact involved in regulation. Monocytes were purified from the peripheral blood of healthy donors and stimulated with GM-CSF (1000 U/mL) and IL-4 (500 U/mL) for 6 days. The differentiated immature DCs, were stimulated with LPS (100 ng/mL) and IFN-γ (1000 U/mL) for 24 hours to generate mature DCs. Tonsillar B cells were purified and stimulated for 5 days on CD40L-transfected NIH3T3 murine fibroblasts in the presence of 0.25μM CpG-ODN 2006. Mature DCs were cultured for 48 hours alone (1:0) or with activated B cells in their supernatant (ratio 1 DC/4 B cells) in the presence of blocking Ab for (A) CD40 (α-CD40L), (B) CD80 and CD86 (α-CD80 and α-CD86), (C) CD54 (α-CD54), (D) CD18 (α-CD18), and (E) CD62L (α-CD62L) at 10 μg/mL final concentration. A specific isotype control for each blocking Ab was used. Six samples were evaluated except for α-CD80 and α-CD86 Ab (4 samples). MFI of HLA-DR, and percentages of CD80^low, CD86^low, and IL-12^low DCs were evaluated by flow cytometry on CD19-negative cells. *P < .05; ns, nonsignificant.