FTY720-mediated toxicity in CLL B cells, MEC-1, Raji, Ramos,697 and RS4;11 B-cell lines: dose and time kinetic analysis. Purified CD19⁺ lymphocytes from patients with CLL (A), MEC (B), Raji (C), Ramos (D), 697 (E), and RS4;11 (F) cells or blasts from a patient with ALL (G) (10⁵ cells/mL medium) were incubated with indicated concentrations of FTY720 or DMSO vehicle for 24 hours (■) or 48 hours (). The cells were stained with annexin V–FITC and PI, as described in “Analysis of cell viability and apoptosis.” The cells were analyzed by flow cytometry, and the data were collected under list mode. The data shown represent percentages of annexin V⁻/PI⁻ viable cells plus or minus SD that are normalized to media control. (CLL B cells, n = 6–15; ALL, n = 4; and cell lines, n = 3; *P < .001 when compared with media control.)