Peripheral blood cell will be collected by apheresis from donors. After ex vivo expansion for 10 days by coculture with irradiated K562-mb15-41BBL cells (Fujisaki et al, Cancer Res 2009; Lapteva et al. Cytotherapy 2012) and T-cell depletion, haploidentical NK cells will be electroporated with anti-CD19-BB-zeta mRNA. Before infusion, patients will receive immunosuppressive therapy to promote temporary engraftment of NK cells. After infusion, they will receive IL-2 to support NK cell viability and expansion in vivo. The effects of NK cell infusion will be determine by comparing MRD levels before and after treatment.