Cutting edge: murine dendritic cells require IL-15R alpha to prime NK cells.

NK cells protect hosts against viral pathogens and transformed cells, and dendritic cells (DCs) play important roles in activating NK cells. We now find that murine IL-15Ralpha-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 dispensable for their activation by DCs. In addition, blockade with anti-IL-15Ralpha and anti-IL-2Rbeta but not anti-IL-2Ralpha-specific Abs prevents NK cell activation by wild-type DCs. Finally, presentation of IL-15 by purified IL-15Ralpha/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 NK cells during NK cell priming. Copyright 2004 The American Association of Immunologists, Inc.