Dendritic cell editing by natural killer cells.

Activated, mature, dendritic cells (DCs) are the main antigen-presenting cells for initiating adaptive immune responses, whereas immature DCs have been implicated in tolerance and induction of regulatory T cells. It is now well established that NK cells are able to discriminate between mature and immature DCs by killing the latter because of their low amount of surface human leukocyte antigen (HLA) class I molecules. Thus, NK cells are thought to play an important regulatory role by selectively editing DCs during the course of immune responses. NK-mediated killing of immature (but not mature) DCs results in selection of immunogenic DCs during the initiation of anti-cancer immune responses. In addition to the removal of inappropriate DCs, NK cells can also shape adaptive immune responses by promoting DC maturation and influencing the polarization of primary T-cell responses. DC-NK cell interactions should be carefully considered in DC-based cancer vaccine strategies. Optimal NK cell activation should be sought to enhance the magnitude and the quality of both innate and adaptive immune responses against tumors.