Predominant development of mature and functional human NK cells in a novel human IL-2-producing transgenic NOG mouse.

We generated a severe immunodeficient NOD/Shi- scid -IL-2Rγ null (NOG) mouse substrain expressing the transgenic human IL-2 gene (NOG–IL-2 Tg). Upon transfer of human cord blood–derived hematopoietic stem cells (HSCs), CD3 − CD56 high CD16 +/− cells developed unexpectedly, predominantly in the NOG–IL-2 Tg (hu-HSC NOG–IL-2 Tg). These cells expressed various NK receptors, including NKp30, NKp44, NKp46, NKG2D, and CD94, as well as a diverse set of killer cell Ig-like receptor molecules at levels comparable to normal human NK cells from the peripheral blood, which is evidence of their maturity. They produced levels of granzyme A as high as in human peripheral blood–derived NK cells, and a considerable amount of perforin protein was detected in the plasma. Human NK cells in hu-HSC NOG–IL-2 Tg produced IFN-γ upon stimulation, and IL-2, IL-15, or IL-12 treatment augmented the in vitro cytotoxicity. Inoculation of K562 leukemia cells into hu-HSC NOG–IL-2 Tg caused complete rejection of the tumor cells, whereas inoculation into hu-HSC NOG fully reconstituted with human B, T, and some NK cells did not. Moreover, when a CCR4 + Hodgkin’s lymphoma cell line was inoculated s.c. into hu-HSC NOG–IL-2 Tg, the tumor growth was significantly suppressed by treatment with a therapeutic humanized anti-CCR4 Ab (mogamulizumab), suggesting that the human NK cells in the mice exerted active Ab-dependent cellular cytotoxicity in vivo. Taken together, these data suggest that the new NOG–IL-2 Tg strain is a unique model that can be used to investigate the biological and pathological functions of human NK cells in vivo.