Critical to innate immunity, the natural killer (NK) cell performs its function of immunosurveillance through its recognition of altered or missing self on damaged, infected, or transformed malignant cells. NK cell receptors responsible for detection of human leukocyte antigen (HLA) class I and class I-like proteins on potential target cells transmit inhibitory and activating signals that integrate to determine NK cell function. Advances in the fields of NK cell receptor biology and immunogenetics have enhanced our understanding of NK cell target recognition and may now guide studies to determine NK cell effects in the clinical setting. Analysis of NK cell receptor-ligand relationships, such as the inhibitory killer immunoglobulin-like receptors (KIRs) and their HLA class I ligands, has revealed the potential for NK cell-mediated benefit in allogeneic hematopoietic stem cell transplantation for hematologic malignancies.
