In vitro activity of K7153A antibody on lymphoma cell lines. (A) Induction of apoptosis measured by annexin V-fluorescein isothiocyanate staining after 20-hour incubation with 10 nM of K7153A antibody, rituximab, or nonbinding huIgG control. (B) Effector activity of K7153A compared with rituximab. ADCC activity (left) as determined by LDH release after 4-hour incubation using purified human NK effector cells and Daudi target cells at a 3:1 ratio. ADCP activity (middle) on PKH26-labeled Ramos cells incubated with isolated human monocyte–derived macrophages at a 1:1 ratio at 37°C for 90 minutes. CDC activity (right) against Ramos cells incubated in the presence of 5% human serum for 2 hours and viability measured by an AlamarBlue assay. (C) Lipid raft redistribution assay with Ramos cells incubated with 10 μg/mL of K7153 or rituximab followed by 0.5% Triton X-100 (lysed) for 15 minutes or left untreated. Mean fluorescence intensity of each sample was measured by flow cytometry.