FIGURE 2.

ULBP2 and -3 are released by the action of metalloproteases, but other mechanisms are also involved. A, CHO transfectants were treated with 1 μm leupeptin (LEU), 1 μm pepstatin (PEP) and a broad metalloproteinase inhibitor, 10 μm BB94. Data are expressed as percentage shedding of the untreated control at 2 h. The inhibition of the release of ULBP2 by the metalloproteinase inhibitor BB94 was the only statistically significant change (t test, p < 0.001), whereas ULBP3 release was only weakly, and not significantly, inhibited by BB94. B, CHO cells were treated with 100 ng/ml of PMA and 5 μm of ionomycin (IONO). The increase of ULBP2 shedding mediated by PMA is statistically significant (p < 0.005). Cells were incubated in the presence of the indicated compounds for 2, 4, 8, and 12 h. Detection of soluble ULBPs in tissue culture supernatant was performed by ELISA.