PBMC-mediated cytotoxicity of ch2B6 and hu2B6-3.5 antibodies against human B-cell lines in vitro. (A) Burkitt lymphoma cell lines, Daudi (top), Raji (middle), and BL41 (bottom) were opsonized with the antibodies at 2 μg/mL: ch2B6 (□), hu2B6-3.5 (▪), ch2B6-N297Q (•), or rituximab (♦), and used as targets for lysis by PBMCs in an 18-hour ¹¹¹In-release assay. (B) Daudi (top) and Raji (bottom) target cells were used as targets for PBMC-mediated lysis in an 18-hour ¹¹¹In-release assay with a fixed E/T ratio of 75:1, and a titration of antibodies: ch2B6 (□), hu2B6-3.5 (▪), ch2B6-N297Q (•), or rituximab (♦), at the designated concentrations. All measurements were performed in triplicate. Error bars represent SD.