CD19^hiFcγRIIb^hi B cells exhibit the increased phagocytic capacity. (A) Freshly purified splenic B cells or FcγRIIb^−/− B cells were incubated with regulatory DCs for 48 hours at a ratio of 1:10 (DC:B). IL-10 in the supernatants was measured. (B) Phagocytic ability of CD19^hiFcγRIIb^hi B cells and conventional splenic CD19⁺ B cells was assessed by flow cytometry of FITC-OVA-IC phagocytosis. Ctrl indicates controls (cells incubated with FITC-OVA-IC at 4°C). (C) The confocal analysis of phagocytic ability of CD19^hiFcγRIIb^hi B cells and conventional splenic CD19⁺ B cells. Representative images of immunofluorescence were stained with Hoechst staining (nuclei). Images were acquired by Leica TCS SP2 confocal microscopy under a 20×/0.70 CS objective lens. (D) Phagocytic ability of CD19^hiFcγRIIb^hi B cells and CD19^hiFcγRIIb^−/− B cells was assessed by flow cytometry of FITC-OVA-IC phagocytosis. Ctrl indicates controls (cells incubated with FITC-OVA-IC at 4°C). (E-F) Splenic CD19⁺ B cells, sorted CD19^hiFcγRIIb^hi B cells, splenic CD19⁺FcγRIIb^−/− B cells, and sorted CD19^hiFcγRIIb^−/− B cells were stimulated with or without IC for 24 hours, respectively, and then assayed for PGE₂ production in the supernatants. Data represent 1 of at least 3 experiments with similar results. (B,D) Numbers indicate the mean fluorescence intensity of test samples. (A,E-F) Data are mean ± SD. **P < .01. NS indicates not significant.