FIGURE 5.

Both ULBP2 and ULBP3 containing supernatants provoke down-regulation of NK cell NKG2D. A, supernatants collected from CHO cells (control) and ULBP-transfected CHO cells were incubated with primary NK cells, prepared from healthy donors, for 48 h. Cell surface NKG2D was then quantitated by flow cytometry. B, t test of five experiments performed with two different donors. Data are expressed as percentage of NKG2D expression observed on NK cells incubated in medium alone. Down-modulation of NKG2D is significant after treatment with both ULBP2 and ULBP3 proteins (p < 0.05 and p < 0.01, respectively). C, ELISA assay to quantitate the amounts of ULBP2 and ULBP3 supernatants used in the down-regulation experiments.