Figure 5.

Quantitative analysis of cytotoxicity mediated by parental NK and MBP NK cells at the single-cell level in hematological cancer cells (K562). (A) Representative time-lapse images of the NK cells (top) and the MBP NK cells (bottom) cocultured with K562 cells were obtained with a confocal microscope. Both types of NK cells were stained with CellTracker^TM blue, and K562 cells were labeled with calcein AM. Compared to the parental NK cells, the MBP NK cells killed the myelogenous leukemia cells very rapidly at all E:T ratios. The red arrows indicate that the hematological cancer cells were still alive, although the NK cells were actively interacted with the cancer cells and seemed to destroy their membranes. (B) Comparison of target lysis time between the NK and MBP NK cells at different E:T ratios. The time was recorded when the first target cell died. The MBP NK cells killed the target cells more efficiently, with less variation, and the E:T ratio did not affect the time required for target lysis. (C) Probability of target cell lysis by the NK and MBP NK cells at different E:T ratios. Compared to the parental NK cells, the MBP NK cells showed superior lysis performance, and the E:T ratio affected lysis performance. Lysis was evaluated by analyzing 319 microwell chambers. The statistical analysis was performed with an unpaired two-tailed t-test, ***, ρ < 0.001; ns = not significant.