Figure 4.

5A6 selectively kills lymphoma cells while sparing PBMCs. (A) Flow cytometry analysis of CD81 and CD20 expression on the indicated lymphoma cell lines and human B cells compared with an isotype control mAb. (B) APC-conjugated 5A6 at decreasing concentration binds preferentially to CFSE-labeled Raji cells when mixed in a 1:1 ratio with VTD-labeled PBMCs. (C) CFSE-labeled Raji cells were mixed at the indicated ratios with VTD-labeled PBMCs, followed by incubation in the presence of 10 µg/ml of 5A6 MsIgG2a and fresh human serum for 1.5 h. Ctrl, control. (D and E) VTD-labeled Raji cells were mixed at a 1:1 ratio with RTD-labeled human purified B cells and incubated with human purified NK cells at a 5:1 ratio in the presence of 2.5 µg of 5A6-MsIgG2a, rituximab, or isotype control for 24 h All experiments were done in triplicate, except in B and C. (C–E) Cell death was measured by Annexin-V and 7-AAD staining. Error bars represent mean ± SEM.