CSF3 and chronic graft versus host disease: In this study, the following main findings were made: 1) in vivo application of G‐CSF not only decreased the percentage of NK cells but also modulated NK subpopulations, leading to an increased ratio of CD56bri to CD56dim subsets and low levels of NK1 cells, and 2) a high dose of NK1 cells infused into allografts correlated with the development of chronic GVHD after transplantation.