HIV envelope binding to α4β7 does not generate a death signal in γδ T cells. (A) Vδ1 or Vδ2 T cells express similar levels of a α4β7 integrin. Cells were stained with primary mouse anti–human α4β7 antibody (NIH AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: α4β7 monoclonal antibody from Dr A. A. Ansari; clone Act-1), then washed and stained with a secondary APC-conjugated rat anti–mouse antibody (BD Biosciences; clone X56). (B) Vδ1 T cells do not express CCR5. Cells were stained with PE-conjugated antibodies for CCR5 (BD Biosciences; clone 2d7) and isotype control, then analyzed by flow cytometry. (C) Vδ1 and Vδ2 T cells bind HIV gp120. Cells were stained with the fluorescein-conjugated HIV gp120 (YU2; Immno Diagnostics) in medium. (D) gp120 binding to Vδ1 T cells was blocked by the α4β7 ligand MAdCAM1. Cells were incubated with or without MAdCAM1 (20 μg/mL; R&D Systems), for 1 hour before staining with fluorescein-conjugated HIV gp120 (YU2). (E) CM-gp120 induces annexin V expression on Vδ2 but not Vδ1 cells. Cells were incubated with or without soluble HIV gp120 glycoprotein (CM strain; 10 μg/mL; NIH AIDS Research and Reference Reagent Program; and HIV-1 gp120 CM envelope protein from Protein Sciences Corp) for 24 hours, then stained with annexin V (BD Biosciences) and 7-aminoactinomycin-D (BD Biosciences). Data are representative of 3 independent experiments. (F) CM-gp120 induced annexin V expression and cell death only in CCR5⁺ Vδ2 cells.