(A) Whole PBMC co-cultured for 4h with 51Cr labeled JHU-029 HNSCC cells coated with 10 μg/mL of cetuximab, panitumumab or isotype controls (IgG1 or IgG2) at different E:T ratios (2.5:1, 5:1 and 10:1). Cetuximab significantly enhanced ADCC compared to panitumumab at an E:T ratio of 10:1. When this experiment was repeated using isolated NK cells (B), cetuximab significantly enhanced ADCC in comparison with panitumumab at all E:T ratios. Data are mean + SEM,*p<0.05, ****p< 0.0001 cetuximab compared with panitumumab.