Infusion of allogeneic natural killer cells in a patient with acute myeloid leukemia in relapse after haploidentical hematopoietic stem cell transplantation

BACKGROUND: Allogeneic donor natural killer (NK)‐cell infusion (NK‐DLI) is a promising immunotherapy for patients with hematologic disorders. CASE REPORT: This report describes the case of a patient who received a single haploidentical NK‐DLI for a relapse of acute myeloid leukemia (AML) after haploidentical hematopoietic stem cell transplantation. He underwent a cytoreductive, immunosuppressive regimen before NK‐DLI and received high‐dose interleukin‐2 in vivo for 8 weeks afterward. RESULTS: No major adverse effect was observed. Prospective phenotypic and functional studies of the NK cells showed major expansion of infused NK cells and, more importantly, of the alloreactive KIR2DL1+KIR2DL2/DL3–NKG2A– subset, which reached 117 × 10⁶ cells/L on Day +14 after NK‐DLI, the greatest expansion of infused alloreactive NK cells reported so far. Infused NK cells conserved their lytic capacities against K562 target cells and primary AML‐mismatched blasts. CONCLUSION: We review the literature to clarify these data and to detail the indications for allogeneic NK‐DLI, the criteria for determining the most suitable donor, the types of conditioning regimens, and the procedures for selecting and activating NK cells.