Fig. 2.

Proliferation and antitumor activity of NK cells in vivo. a The NK cells that were stained with CFSE on day 0 (D0) before injection had undergone multiple cell divisions by day 5 (D5) and day 30 (D30) after transplantation. Gates were set on CD56⁺ cells. Solid line in the histogram was unstained control. b Mice that were injected with human CD45⁺CD19⁺ SEM leukemic cells alone (upper panel) had higher numbers of leukemia cells in the spleen at 1 month after transplantation, as compared with mice injected with leukemic cells and purified NK cells (middle panel) in a very low effector to target cell ratio (1:1) (p=0.015 by Wilcoxon rank-sum test). Black lines in the histograms depict human CD45 staining of splenic cells from normal unmanipulated mice. Results shown in (a) and (b) are from two independent experiments on ten mice injected with cells from different donors. c Mice that were injected with NB1691 neuroblastoma cells alone had higher numbers of tumor nodules in the liver at 1 month after transplantation (left panel) compared with mice injected with neuroblastoma cells and purified NK cells (1:1 ratio) (right panel; p=0.046 by rank-sum test). Results shown in (c) are representative of two independent experiments on eight mice injected with cells from different donors.