ADCC activity. Ab-dependent cell-mediated cytotoxicity (ADCC) activity (% cytolysis) on Ramos cells (E:T ratio 25:1) of mAb 37.1 in comparison with non–Fc-engineered parental mAb (37.1-wt; A) and rituximab (B). ADCC activity on primary CLL cells of 30 μg/mL of mAb 37.1 and rituximab showing (C) potency (EC₅₀ in nanograms per milliliter) and (D) efficacy (maximal cell lysis in %). Bars represent mean of 6 donors; SD is indicated.