NK cells play a critical role in killing cancer cells that are remain after surgery/radiation and/or chemotherapy, so-called “residual disease.” Modern cancer therapy can effectively eliminate most of cancer in a patient. To eliminate all cancer cells, the patient’s immune system needs to do its part and kill the residual disease. For instance, patients with AML often receive an induction chemotherapy regimen called 7+3 (7 days of cytarabine and 3 days of daunorubicin). Of these patients, 40% are cured (“survivors”) while 60% relapse (“relapsers”). The difference between a survivors and relapsers is the patient’s immune system. The NK cells of the survivors kill the residual disease while the NK cells of relapsers do not kill the residual disease. The failure of the immune system to eliminate residual disease is the cause of the cancer relapse.