Killing of ARH B-cells and fresh tumors (CLL and HCL) by CD20 mAbs with human effectors. (A-B) Lysis of ARH-77 lymphoma cells was measured in 3-hour ⁵¹Cr release assays. (A) The influence of antibody concentration was investigated using unfractionated blood from healthy donors as effector source. Symbols: rituximab, ▪; 7D8, ▴; 2F2, ▾ ; and 11B8, •. This figure shows the mean ± SEM of 4 separate experiments determining the percent specific ⁵¹Cr-release. (B) To identify individual effector mechanisms, human blood (whole blood) was fractionated into polymorphonuclear (PMN) or mononuclear (MNC) cells, or into complement-containing plasma (plasma). Antibodies were used at 10 μg/mL, and isolated PMNs and MNCs at an effector-to-target cell ratio of 40:1. Data represent the mean ± SEM of 8 separate experiments determining percent specific ⁵¹Cr-release. (C-D) Similar experiments were performed against ⁵¹Cr-labeled, freshly isolated lymphoma cells. As effector source, we used unfractionated blood from healthy volunteers, which was fractionated into polymorphonuclear (PMN) or mononuclear (MNC) cells, or into complement-containing plasma (plasma). (C) Mean ± SEM of experiments determining percent specific ⁵¹Cr-release from 8 primary hairy cell leukemias. (D) Data from 16 primary B-CLLs. All mAbs were used at 10 μg/mL, and isolated PMNs or MNCs at an effector-to-target cell ratio of 40:1. Data are presented as the mean ± SEM of the percent specific ⁵¹Cr-release.