mAb-induced ROS triggers cell death in primary CLL samples. (A) Primary CLL cells were treated with mAbs (10 μg/mL) and 4 hours later stained with HE to assess ROS generation by flow cytometry. Representative data from 1 patient sample is shown. GA101 induces greater ROS than rituximab in primary B-CLL cells. (B) Dual staining of GA101-treated primary CLL cells with HE and annexin V Cy 5.5 to detect ROS and cell death, respectively confirms that ROS generation coincides with cell death in CLL cells. (C) CLL cells from 3 different patients were treated with mAb in the presence or absence of tiron and cell death was assessed after 4 hours by annexin V–Cy5.5 and 7-AAD costaining. Mean + SEM of cell death in the 3 independent patient samples are shown. Because of the heterogeneous levels of basal apoptosis in primary CLL samples, data are expressed as percentage cell death over control.