In vitro and in vivo activity of c1F6 requires functional Fc–Fcγ receptor interaction. (A) Binding of c1F6 and c1F6v to CD70⁺ cells was detected with a fluorochrome-conjugated anti–human IgG antibody by flow cytometry. ADCC, CDC, and ADCP activities of c1F6 (solid squares) compared with c1F6v (open diamonds) or nonbinding IgG1 (open circles) were measured as described in “Materials and methods.” (B) Survival curve of mice injected intravenously with 1 × 10⁶ Raji tumor cells then treated one day later with 4 mg/kg c1F6 or c1F6v (n = 10 per group). The P value indicates difference between the c1F6-treated and untreated groups.