Degranulation by resting NK cells induced by NKG2D and 2B4 synergism. NK cells were incubated for 2 hours either alone or with P815 cells and mAbs as specified. Cells were stained with anti-CD56 and isotype control or anti-CD107a mAbs. Plots were gated on a forward scatter/side scatter lymphocyte gate. The experiment is representative of 7 independent experiments.