MNC-mediated lysis of A431 cells is enhanced by low fucosylated 2F8-C, whereas PMN-mediated lysis is diminished. To analyze Fc-mediated effector functions of 2F8-C and 2F8-H antibodies, both antibody preparations were compared in their capacity to trigger ADCC of A431 cells with isolated (A) MNCs or (C) PMNs as effector cells and variation of antibody concentrations at a fixed E/T ratio (80:1). To define Fc receptors involved in (B) MNC- or (D) PMN-mediated target cell killing, ADCC assays were performed in the presence of F(ab′)2 fragments of Fcγ receptor blocking antibodies AT10 (FcγRII), or 3G8 (FcγRIII), or control F(ab′)2 fragments (all at 10 μg/mL). 2F8-C (●), 2F8-H (○), human IgG1 control antibody (Δ). Data from experiments with 6 (A,C) or 3 (B,D) different donors, respectively, are presented as means plus or minus SEM. *Significant differences in killing between 2F8-C and 2F8-H. #Significant blockade compared with control treated samples (P < .05).
