FIG. 5.

Inhibition of apoptosis of Ramos Burkitt's lymphoma B cells. B cells were preincubated with (shaded bars) or without (open bars) Z-VAD-fmk (A) or with (shaded bars) or without (open bars) cloned Stx1 B subunit (B) or were preincubated with (shaded bars) or without (open bars) brefeldin A (BFA) (C). The Ramos cells were next incubated at 37°C for 18 h with camptothecin, Stx holotoxins, or their cloned B subunits. These Ramos cells were then labeled with Annexin V-FITC and propidium iodide, and the proportion of early and late apoptotic cells in each sample was determined by flow cytometry analysis. The error bars represent the standard deviations (n = 5).