The importance of natural killer cell killer immunoglobulin-like receptor-mismatch in transplant outcomes.

PURPOSE OF REVIEW: In recent years, the rules of engagement between natural killer (NK) cells and their targets have become better defined with the identification of an array of NK surface molecules, notably the killer immunoglobulin-like (KIR) receptors and their ligands on target cells through which signals of activation or suppression of NK function are mediated. After allogeneic stem cell transplantation (SCT), the opportunity for NK cell activation can occur both in human leucocyte antigen (HLA) matched and HLA mismatched pairs. Although less well explored in HLA identical transplants, many studies confirm the importance of NK KIR mismatching in the graft-versus-leukemia effect in haploidentical (haplo) SCT and this has stimulated recent research to better define the role of NK mismatching on transplant outcome. In this review, we describe recent progress in identifying favorable and unfavorable NK matching in SCT.

RECENT FINDINGS: Recent studies focus less on KIR-HLA mismatching and more on KIR genes as tools to predict alloreactivity via NK licensing and activating KIR.

SUMMARY: Current results show that transplant outcomes could be improved by judicious selection of favorable donors.