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.
After revision:  We then apply the method to data from experiments with highly migratory human-derived natural killer (NK) cells that were derived from two different human donors. We find for one of the donors an attractive interaction between the NK cells, pointing to a cooperative behavior of these immune cells. When adding nearly stationary K562 tumor cells as targets that are dispersed in a 3-dimensional collagen matrix.