Cutting edge:: Murine dendritic cells require IL-15Rα to prime NK cells

NK cells protect hosts against viral pathogens and transformed cells, and dendritic cells (DCs) play important roles inactivating NK cells. We now find that murine IL15Ralpha-deficient DCs fail to support NK cell cytolytic activity and elaboration of IFN-gamma, despite the fact that these DCs express normal levels of costimulatory molecules and IL-12. By contrast, IL-15Ralpha expression on NK cells is entirely dispensible for their activation by DCs. In addition, blockade with anti-IL-15Ralphaandanti-IL-2Rbeta butnotanti-IL-2Ralpha-specific Abs prevents NK cell activation by wildtype DO. Finally, presentation of IL-15 by purified IL15Ralpha/Fc in trans synergizes with IL-12 to support NK cell priming. These findings suggest that murine DCs require IL-15Ralpha to present IL-15 in trans to NKcells during NK cell priming.