Interaction between B cells and DCs. (A) Human monocyte-derived DCs were cultured in triplicates alone or were cocultured with human CD19⁺ B cells, which were activated via CD40L or CD40L+CpG, at a DC/B-cell ratio of 1:4 for 48 hours. Subsequently, the cell surface expression of CD80, CD86, and HLA-DR was determined using a Gallios flow cytometer (Beckman Coulter, Krefeld, Germany). The bar charts represent the mean percentage of positive DCs ± SD. (B) To determine the effect of the initial B-cell stimulation on their survival in the coculture, we determined the percentage of remaining B cells among the total CD45⁺ cells after 48 hours in the coculture with DCs at a DC/B-cell ratio of 1:4. Shown are the mean percentages of CD19⁺ B cells ± SD. **P < .01.