Figure 2

B leukemia cells are sensitive to GBR 401 mediated ADCC in vitro . A/ Raji cells (Burkitt’s lymphomas, CD19+ CD20+), were incubated during 4 hr with 0.5 μg/mL of mAbs in the presence of purified NK cells from random donors (effector/target ratio of 5). Target cell death was measured by LDH release. Specific ADCC (%) was calculated by the formula: (Sample release – spontaneous release)/(Max release – spontaneous release) x100. The graph shows the average specific ADCC (%) ± SD of triplicates obtained with one NK cell donor representative of several different donors. The Table 1 presents the data summary for all donors. GBR 401(F) is the fully fucosylated variant of GBR 401. B/ cell lines Raji, Ramos (Burkitt’s lymphomas, CD19+ CD20+), Namalwa (Burkitt’s lymphoma, CD19+ CD20low) and SU-DHL-6 (Human diffuse histiocytic lymphoma, CD19+ CD20+) were incubated during 4 hr with various concentration of mAbs in the presence of purified NK cells from random donors (effector/target ratio of 5). Target cell death was measured as in (A). The graphs show the average specific ADCC (%) ± SD of triplicates. Each graph shows a representative result obtained from at least four different NK cell donors. The Table 1 presents the data summary for all donors. C + D/ PBMC from patients with CLL (n = 13) (C) or B cell lymphomas (n = 4) (D) were incubated with peripheral blood NK cells (effectors/target ratio of 1) from two different healthy volunteer donors with various concentration of mAbs (0.005 ng/mL - 5 μg/mL) for 24 hr. HER was used as control mAb. The malignant B cells were stained for cell death by 7AAD and analyzed by flow cytometry. Figures show EC₅₀ values and maximum killing percentage of specific ADCC for each NK donor and leukemia sample combination.