B-cell depletion of whole-blood samples. Depletion (in %) of autologous B cells (A) and spiked Ramos cells (B) assessed by quantitative FACS analysis (TruCount) of whole-blood samples from healthy individuals after 3-hour incubation with 30 μg/mL of mAb 37.1 and rituximab. Bars represent mean of 3 donors; SD is indicated. In whole-blood assays with primary CLL samples, mAb 37.1 shows concentration-dependent CLL cell depletion whereas rituximab displays only marginal activity after 3-hour (C) and 8-hour (D) incubation. Bars represent mean of 8 donors; SD is indicated.