Induction of apoptosis in CD19⁺ cells after incubation with rGel or rGel/BLyS. Primary PBMNCs derived from (A) 9 previously treated or (B) 11 previously untreated patients were incubated with either rGel (□) or rGel/BLyS (▪) for 96 hours and specific apoptosis in CD19⁺ cells was measured using flow cytometry after staining cells with CD19-APC, annexin V–PE, and 7AAD. Specific apoptosis in comparison with control cell death was calculated and presented as percent of control.