Development of a quantitative, cell-line based assay to measure ADCC activity mediated by therapeutic antibodies

Antibody-dependent cellular cytotoxicity (ADCC) contributes to clinical efficacy of a broad range of antibody therapeutics. However, reproducible quantitation of ADCC activity on a cellular level remains highly challenging, as ADCC assays rely on primary effector cells associated with laborious cell purification procedures, resulting in highly donor-dependent results. Here, we report the development of an in vitro ADCC method based on an engineered human natural killer cell line as effectors. While eliminating the limitations of primary cells, this assay exhibits all the hallmarks of traditional ADCC assay systems. We have used this assay to measure the ADCC activity of a humanized IgG1 antibody directed against the human CD20 antigen. Our data show that this assay is capable to measure small changes in ADCC and can therefore be used to test therapeutic antibodies against cell-surface targets for their depleting activity.