BCR activation reduces the ability of B cells to repair SLO-mediated plasma membrane damage and SLO-induced CTB endocytosis. (A) Percentage of cells repaired after SLO wounding in the presence or absence of BCR activation. B cells were incubated without (−Ab) or with Fab (10 µg/ml), F(ab′)2 anti–mouse IgM (10 µg/ml), or biotinylated Fab (bFab; 10 µg/ml) plus streptavidin (strep; 5 µg/ml) at 4°C and treated with SLO for 5 min at 37°C, followed by PI staining and flow cytometry. Shown is the mean (± SD) of three independent experiments. (B) The percentage of surface-labeled CTB internalized in the presence or absence of SLO and BCR cross-linking. B cells were incubated with (+XL) or without (−XL) gold anti–mouse IgM (10 µg/ml), biotin–CTB (2 µg/ml), gold-streptavidin (2 µg/ml), and SLO at 4°C and warmed up to 37°C for 1 min. Cells were then processed for TEM. The numbers of gold particles associated with and inside individual cells were counted. Shown is the mean (± SD) of >20 randomly selected cell profiles per condition from two independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001.