BLyS stimulation promotes B-cell survival and growth. (A,B) BLyS sustains B cells ex vivo. Mature small resting murine splenic B cells positively selected with anti-CD23 and streptavidin magnetic beads were cultured for 4 days with or without 100 ng/mL huBLyS. The number of viable cells was determined daily by trypan blue exclusion (A) or by flow cytometry using blue fluorescent vital dye (B); data are the arithmetic mean (± SD) of 2 separate experiments. (C) B cells cultured with BLyS resist apoptosis. Apoptosis was determined by flow cytometry using PI on CD23⁺ B cells freshly prepared or cultured for 3 days with and without 100 ng/mL of huBLyS. The results are representative of 3 independent experiments. PI indicates propidium iodide. (D) B cells cultured with BLyS maintain cell size ex vivo. Percoll-purified B cells were cultured for 5 days in CM with and without 50 ng/mL of rhuBLyS and sized daily using a Coulter Z2 particle analyzer. Dead cells were excluded by sedimentation over Percoll. Data shown are the arithmetic means (±SD) for 3 independent experiments with statistical comparisons between unstimulated and BlyS-stimulated B cells indicated (**P < .01; ***P < .001). (E) BLyS promotes increased glucose metabolism. Glucose use by cultured CD23⁺ B cells left unstimulated or stimulated with 100 ng/mL rhuBLyS, 5 μg/mL anti-Ig or 0.5 μg/mL of anti-CD40 for 2 days. Results are the arithmetic means (± SD) for 2 independent experiments.