To examine anti-leukemia activity of memory-like NK cells with enhanced IFNγ production induced by in vivo IL pre-activation and re-stimulation, Rag1KO B6 (CD45.2+) mice were divided into three groups: the vacant control group, in which mice received PBS; the negative control group, in which mice received IL pre-activation only; and the IL re-stimulation group, in which mice received both IL pre-activation and re-stimulation as described above. This evidence concerns the gene IFNG and leukemia.