The 5F11 mediates potent ADCC OF CD30⁺ tumor cells. (A) L540 cells were used as targets for lysis by IFN-γ-treated human monocytes. Monocytes were purified from normal adult source leukopacs (Biological Specialty Corp) and cultured in macrophage serum-free medium (M-SFM; Gibco) supplemented with 10% FBS and IFN-γ (1000 u/mL; R&D Systems) for 2 days. Target cells were labeled with 100 μCi (3.7 MBq) of ⁵¹Cr for 1 to 2 hours prior to combining with effector cells and HuMAb and then incubated for 16 hours at 37°C. Cytotoxicity was calculated by the formula: % lysis = (experimental CPM - target leak CPM)/(detergent lysis CPM - target leak CPM) × 100. Specific lysis = % lysis with HuMAb - % lysis without HuMAb. All measurements were done in triplicate and error bars represent standard deviations. (B) L540 cells were used as targets for lysis by fresh human mononuclear cells purified from heparinized whole blood by ficoll hypaque density centrifugation. Target cells were labeled with 100 μCi (3.7 MBq) of ⁵¹Cr for 1 to 2 hours prior to combining with effector cells and HuMAb. After incubation for 16 hours at 37°C supernatants were collected and analyzed for radioactivity. Cytotoxicity was calculated as in panel A. All measurements were done in triplicate and error bars represent standard deviations.