IFN-γ release by NK cells is induced through immobilized ULBP2-BB4 in a NKG2D-dependent way. Purified NK cells and PBLs of 2 healthy donors were incubated with IL-2 (10 U/mL, left part of each panel, patterned bars) or IL-2 plus IL-15 (100 ng/mL, right part of each panel, white bars) overnight and stimulated through immobilized ULBP2-BB4, immobilized BB4, or PBS for 48 hours. The IFN-γ concentration of the supernatant was estimated using ELISA and is indicated in nanograms per milliliter. In blocking experiments, an anti-NKG2D antibody (10 μg/mL) was added to the effector cells stimulated with IL-2/IL-15 and ULBP2-BB4 (right column in each panel, white bar. Two independent experiments, each measured in duplicate, were performed for each donor, and the mean ± SD is indicated.