KILR CD16 Effector Cells

Therapeutic monoclonal antibodies are able to bind to their target antigen and can also bind to Fc receptors found on the surface of effector immune cells. This results in target cell death by Antibody-Dependent Cell-mediated Cytotoxicity (ADCC). Traditional ADCC assays can be complex and require the use of freshly isolated primary human cells such as PBMCs or NK cells. However, these cells have inherent inter-donor variability and as such cannot be implemented in QC lot release assays where control over reagents is strictly controlled. KILR CD16 effector cells from Eurofins DiscoverX are single donor-derived human primary cells which mediate target cell death. The cells are uniformly manufactured, maintain their T cell phenotype (CD3 and CD8 positive) and are transfected with the CD16 receptor (FcγRIIIa-V158). These cells are therefore capable of inducing target cell death in ADCC assays in a similar manner to cells isolated from blood. The uniformity of the cells removes the issue of inter-donor variability which can often result in higher failure rates during assays, leading to one of the issues faced when using an ADCC assay for lot release of a monoclonal antibody.

 

 Dilutional Linearity R2Average Fold IncreaseAverage EC50 (ng/mL)Maximal Inaccuracy%CV Intermediate Precision
KILR Cells0.99893.792.712.1%11%
Purified NK Cells0.98082.094.419%8%

Using the molecule rituximab as a model, we performed a qualification study replacing purified NK effector cells isolated from blood with the KILR CD16 effector cells. Accurate and precise results were obtained over the range of concentrations tested (50% to 200%), between different operators and between different vials of effector cells thawed on different days. While the precision of the assay using both KILR CD16 effector cells and purified NK cells was comparable, the fold response induced by the KILR CD16 effector cells was greater, providing a more consistent assay window for assessing parallelism. This demonstrates that the KILR CD16 effector cells represent a more suitable system for QC and lot release assays.

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