Enhancement of cytotoxic membrane damage by DEX. (A) Purified CLL cells were cultured with or without DEX, the monoclonal CD20 antibody ofatumumab (70 μg/mL), or rabbit complement (1:40 final dilution). Cells were stained with 7AAD after 48 hours and analyzed by flow cytometry. Specific death is the difference between the percentages of 7AAD⁺ cells in control samples and treated samples. The averages and standard errors of the results for the indicated sample numbers are shown. (B) CLL cells from 4 different patients were cultured with DEX, rabbit complement, and the indicated concentrations of ofatumumab, alemtuzumab, and rituximab. Specific death was measured after 48 hours. (C) The averages and standard errors for the results with individual patient samples are shown and indicate that alemtuzumab, which causes more membrane damage than the CD20 antibodies, had greater cytotoxic activity in the presence of DEX. (D) Purified CLL cells were cultured with or without DEX in the presence or absence of the indicated doses of ionomycin before measuring specific death. (E) Purified CLL cells from 52 different patients were treated with DEX in RPMI-1640, transferrin, and 0.02% lipid-rich albumax or with RPMI-1640, transferrin, and 0.02% fatty acid–free (FAF) albumin to remove free fatty acids that could damage cell membranes in culture. Specific death after 48 hours was significantly lower in FAF albumin. **P < .01; *P < .05.