The importance of an efficient NK cell response for the promotion of a favorable outcome to viral infections has been demonstrated in both mice and humans [2, 7] , and the rapid activation of NK cells after infection is a hallmark of their potency as innate immune system effectors [2] . Increasing evidence supports the idea that optimal coordination of immune responses involves an intricate relationship between NK cells and other innate leukocytes. For example, several reports have documented the importance of NK/DC ''crosstalk'' for the reciprocal activation of these cell types and in the promotion of antitumor immunity as recently reviewed [3, 8] . Others have shown the involvement of macrophages as an intermediary in the activation of NK cells via Va14i NK T cells [9] . NK cells have also been shown to have the capacity to interact with neighboring NK cells as well as T cells to stimulate cellular proliferation [10, 11] .