Alloreactive natural killer cells in hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) for leukemia can play a major role in reducing the risk of relapse by inducing a graft versus leukemia (GVL) effect. Here, we review the effectiveness of mismatching inhibitory killer-cell-immunoglobulin-like receptors (KIR) on donor natural killer (NK) cells as a mechanism for GVL. We review the range of KIR and the importance of T cell and NK cell content of the graft, together with considerations of the graft source. Further understanding of conditioning and mechanisms to reduce graft versus host disease (GVHD) will improve our ability to manipulate NK cells in HSCT.