Notch activation enhances IFNgamma secretion by human peripheral blood and decidual NK cells.

NK cells specialize in killing tumor cells and virally infected cells and also possess non-cytotoxic functions, which include secretion of a variety of cytokines and growth factors. Their activity is mediated by a vast repertoire of inhibitory and activating NK receptors. Recently, it was demonstrated that ligation of the Notch receptor plays a significant role not only in T cell development but also in human T cell and mouse NK cell activation. However, the involvement of Notch triggering in human NK cell activity has not yet been determined. Here we show that Notch1 and Notch2, but not Notch3 and Notch 4, are expressed in human peripheral blood NK cells and in decidual NK cells. We demonstrate that in peripheral blood NK cells only the Notch ligand Delta4 could interact with Notch, whereas in decidual NK cells both Delta1 and Delta4 can interact with Notch. Finally, we show that Notch activation in these cells leads to increased secretion of IFNgamma. We therefore present here a new function of the Notch receptors as enhancers of peripheral blood NK cell and decidual NK cell functions.