HIV-1 Vpr enhances the killing of HIV-1–infected CD4⁺ T lymphocytes by autologous NK cells. Human primary CD4⁺ T lymphocytes were mock-infected or infected with infectious CCR5-tropic HxBru.ADA.GFP or HxBru(Vpr-)ADA.GFP at an MOI of 0.5. After 5 days, mock-infected or GFP-expressing infected primary CD4⁺ T lymphocytes were sorted and subsequently exposed to autologous primary NK cells in a 4-hour ⁵¹Cr release assay in the absence (A) or presence (B) of interfering Abs to NKG2D (α-NKG2D) or matched-IgG control Abs (IgG), as indicated. Error bars represent SEM. Results shown are representative of the data obtained with 3 different donors.