Feasibility and Safety of Donor-derived NK-cell Infusions for Leukemia Relapse Prophylaxis After Hematopoietic Stem Cell Transplantation

This study tests whether infusions of natural killer (NK) cells donated by a matched donor can help prevent leukemia from coming back after a bone marrow transplant (stem cell transplant). NK cells are part of the immune system and can attack cancer cells. **You may be eligible if...** - You are between 0 and 25 years old (or your guardian consents if you are under 18) - You have been diagnosed with acute myeloid leukemia, acute lymphoblastic leukemia, or certain other high-risk blood cancers - You have undergone or are planning a haploidentical stem cell transplant (from a half-matched donor) - Your disease meets specific criteria for high relapse risk **You may NOT be eligible if...** - You have active uncontrolled infection - Your organ function does not meet the required thresholds - Your cancer has relapsed after transplant Talk to your doctor to see if this trial is right for you.