ADCC, CDC, and proapoptotic activities of recombinant antibodies and immunocytokines. (A) The ability of resting human PBMCs to mediate the specific lysis of CD20⁺ Daudi lymphoma cells was measured in a 4-hour ADCC assay as described in “Materials and methods.” Proteins included DI-Leu16-IL-2 (▪), DI-Leu16 antibody (□), rituximab (♦), chLeu16-IL-2 (▴), chLeu16 antibody (▵), enzymatically deglycosylated DI-Leu16-IL-2 (○) and a nontargeting IL-2 immunocytokine (×). (B) CDC activity was measured as described in “Materials and methods” using the same proteins as in panel A. (C) Early apoptosis of Daudi cells induced by the indicated antibodies or immunocytokine (50 μg/mL) was measured by Annexin-V staining and FACS analysis. The anti-EpCAM humanized antibody, huKS-1/4, was used as a nonbinding IgG1 antibody control.