In vitro cytotoxicity of IL-15 activated CIK cells was significantly enhanced compared to IL-2 activated controls and in vivo anti-leukemic efficacy extensively tested in several established mouse models of human leukemia xenografts, showed homing of IL-15 activated CIK cells to leukemia sites, leukemia control, and when repeatedly given complete disease clearance indicated by improved survival (15). Here, IL2 is linked to leukemia.