Functional analysis of FO and MZ B cells of BCL10 Tg mice. (A) FACS-purified B cells were cultured for 72 hours, then stained for 7AAD and Annexin V detection, and viable cells were determined by FACS. The data (mean ± SEM) shown are from 4 independent experiments. *P < .05. (B) Apoptosis induced by BCR ligation. Purified B cells were stimulated with anti-IgM (10 μg/mL) for 72 hours, stained for 7AAD and annexin V detection, and analyzed by FACS. *P < .05, **P < .01. (C) Proliferation of FO and MZ B cells in response to stimulation with anti-IgM and LPS. Cells labeled with CFSE were cultured in the presence of F(ab)′₂ anti-IgMμ (20 μg/mL) or LPS (1 mg/mL) for 72 hours. The cells were then stained to detect 7AAD and annexin V and analyzed by FACS, with the histograms gated on viable cells. The numbers are percentages of cells undergoing more than 2 divisions. Data (mean ± SE) are from 3 independent experiments; ^aP = .12. (D) B-cell proliferation in vivo. Mice were injected intraperitoneally with BrdU at 12-hour intervals for 7 days. Splenocytes were stained with Abs to B220, CD21, and CD23 to identify B-cell subsets, then fixed, permeabilized, and stained to assess incorporation of BrdU by FACS. Numbers (mean ± SD) indicate the percentages of BrdU⁺ cells from 5 to 6 mice in each group. *P < .05 compared with WT controls.