Abstract
Natural killer (NK) cells are key players of the innate immune system. Due to their rapid cytotoxicity against infectious pathogens, hematologic malignancies, and solid tumors, NK cells represent solid candidates for cell-based immunotherapy. Despite the progress made in recent years, the heterogeneity in their cytotoxic behavior represents a drawback. With the goal of screening the intrinsic diversity of NK cells, droplet-based microfluidic technology is exploited to develop a single-cell time-efficient cytotoxicity assay. Toward this end, NK-92 cells are coencapsulated with hematological tumor cell lines in water-in-oil droplets of different sizes and their cytotoxic activity is evaluated. The effect of droplet-based confinement on NK cytotoxicity is investigated by controlling the droplet volume. The successful optimization of the droplet size allows for time efficiency compared to cytotoxicity assays based on flow cytometry. Additionally, the ability of individual NK-92 cells to kill multiple target cells in series is explored, expanding the knowledge about the serial killing process dynamics. The developed droplet-based microfluidic assay does not require the labeling of NK cells and represents a step toward developing of a forthcoming process for the selection of NK cells with the highest cytotoxicity against specific targets.
Highlights
Natural killer (NK) cells represent fundamental members of the innate immune system
By developing a single-cell cytotoxicity assay inside droplet-based confinements we aimed to overcome the spatial- and temporal-related issues that affect standard bulk live imaging and flow cytometry assays, respectively
Note that since NK cells can kill up to seven target cells in a row, in this study, we focused our investigation on the early commencement of the serial killing behavior of NK-92 cells, evaluating their capability to serially kill up to two or three target cells
Summary
Natural killer (NK) cells represent fundamental members of the innate immune system. These highly cytotoxic immune effectors mediate rapid and broad cytotoxicity against infectious pathogens, hematologic malignancies, and a number of different solid tumors without prior target recognition.[1]. Approximately 7−10% of NK cells exhibit the ability to kill repeatedly, up to seven times in a row having been observed.[6−8] Current cytotoxicity assays are carried out in bulk and are based on the evaluation of radioactive[9] or fluorescent[10] labels released or changing within targeted cancer cells lysed by cytotoxic immune cells, respectively. These bulk assays deliver averaged results for an entire batch of cells, effectively camouflaging molecular-level differences between individual NK cells. The development of single-cell, high-throughput ex vivo screening methodologies is fundamental to both investigate and fine-tune the immunological process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
