Before revision:  We then apply the method to data from experiments with highly migratory human-derived natural killer (NK) cells and nearly stationary K562 tumor cells as targets that are dispersed in a 3-dimensional collagen matrix. Although NK cells find and attack K562 cells with high efficiency, we show that the attacks are consistent with a target-blind random walk.
After revision:  We then apply the method to data from experiments with highly migratory human-derived natural killer (NK) cells and nearly stationary K562 tumor cells to the system, we find a repulsive interaction between K562 cells with high efficiency, we show that the attacks are consistent with a target-blind random walk.