Up-regulation of cell-surface NKG2D ligands in cells expressing HIV-1 Vpr. (A) Human primary CD4⁺ T lymphocytes were transduced with lentiviral vectors expressing GFP alone (WPI) or coexpressing GFP and VprWT (WPI-VprWT). GFP-expressing cells were monitored for ULBP-2 cell-surface expression by flow cytometry 48 hours after transduction using specific mAbs directed against ULBP-2 and appropriate fluorochrome-conjugated secondary reagents. (B) CEM.NKR T cells were transduced with WPI-VprWT or WPI lentiviral vectors or treated with APC (4μM) as indicated. Cell-surface expression of NKG2D ligands was monitored on the GFP-expressing cells 48 hours after transduction or after a 24-hour treatment with APC, using specific mAbs directed against ULBP-1, -2, and -3, MICA, MICB, and appropriate fluorochrome-conjugated secondary reagents. MFI values were calculated by subtracting the corresponding isotype control values (dashed line). Results shown are representative of the data obtained from at least 2 independent experiments.