Objective

Natural Killer (NK) cells are innate lymphocytes that play a crucial role in antiviral protection and cancer immunosurveillance. Expansion and activation of NK cells is currently investigated as a potential cell therapy with already substantial results in hematological cancers. We have previously reported an imaging-based screening platform for assessment of the cytotoxic potential of individual NK cells within larger populations. In this assay, human primary NK cells are distributed across a silicon–glass microchip containing 32,400 individual microwells loaded with tumor target cells. Through fluorescence screening and automated image analysis, the numbers of NK and live or dead target cells in each well can be assessed at different time points after initial mixing. It became evident that a small fraction of highly cytotoxic NK cells were responsible for a substantial portion of the killing. We are therefore interested in investigating more features of the most efficient killers. As the cells are still trapped after the cytotoxic screen further characterization of the serial killing NK cells is also possible. On the one hand, we present here an automated single-cell isolation system that allows for specific retrieval and subsequent analysis of these cells. On the other hand, we are currently developing methods for investigation of the long-term outcome of the serial killing NK cells, such as proliferation or viability long after initiation of target-cell interactions. These approaches could greatly benefit clinical applications, e.g., in the generation of highly specific and cytotoxic cells for adoptive immunotherapy.