Fig. 4. Human memory-like NK cells control human leukemia in an NSG xenograft model.

(A) Experimental design for (B) to (E). rhIL-2, recombinant human IL-2; QOD, every other day. (B to E) NSG mice received human NK cell adoptive transfers as indicated in (A). Representative flow cytometry at day 7 after transfer shows engraftment of human memory-like NK cells in the indicated tissues from a representative donor. Both CD56^bright and CD56^dim subsets are detectable. (C) Summary of data from (B) demonstrating the engraftment of control and memory-like NKcells, with abundance identified as the ratio to murine CD45⁺ mononuclear cells. (D) Control or memory-like NK cells were administered to NSG mice as in (A). After 7 days, splenocytes were isolated and restimulated with K562 for 6 hours, followed by assessment of human NK cells for IFN-γ production. Numbers depict the percentages of cells within the indicated regions. (E) Summary of data from (D) showing the means ± SD of percent IFN-γ –positive NK cells from the indicated NK cell subsets. Statistical analysis was performed with Mann-Whitney test. (F) Experimental design for (G) to (I). (G to I) K562-luc was injected intravenously into NSG mice. After 4 days, BLI was performed to ensure leukemia engraftment, and control or memory-like NK cells were administered to the mice. The mice were treated with rhIL-2 every other day and monitored for tumor burden (BLI) and survival. (G) Representative BLI of recipient mice engrafted with K562-luc on the indicated day after tumor administration. (H) Summary of serial BLI measurements that show reduced tumor burden in mice receiving memory-like NK cells compared to control NK cells. Differences were determined using analysis of variance (ANOVA). (I) Mice were treated as in (F), monitored for survival, and analyzed using the log-rank test. PBS, phosphate-buffered saline. Summary data are from two to three experiments with n = 12 to 24 mice per group represented as means ± SEM.