Figure 6. Enhancement of PMN-mediated ADCC by increased FcγRIIa binding is not limited to specific FcγRIIIb or FcγRIIa polymorphisms. (A-D) The effect of distinct FcγRIIIb (FcγRIIIb-NA1/NA2; A, B) and FcγRIIa (FcγRIIa-131H/R; C, D) polymorphisms on the extent of PMN-mediated ADCC against A431 cells by Fc-engineered anti-EGFR antibody variants was analyzed by 51chromium release experiments utilizing either untreated PMN (A, C) or GM-CSF stimulated PMN (B, C) from healthy blood donors. Data are presented as mean ± SEM from at least three independent experiments with different blood donors, except for FcγRIIIb-NA1/NA1 (n = 1). * P ≤ 0.05 for wild type antibody vs. antibody variants; # P ≤ 0.05 for S239D/I332E/G236A vs. S239D/I332E.