CD4⁺ T-lymphocytes infected with HIV-1 express NKG2D ligands ULBP -1, -2, and -3 but not MICA or MICB. (Top panels) Uninfected and HIV-1_SF162–infected primary T-cell blasts were stained with antibodies directed to ULBP-1, -2, and -3, and a rabbit antimouse secondary reagent followed by intracellular staining with a monoclonal human anti-p24 antibody. (Bottom panels) The NKG2D ligands MICA and MICB were detected using specific antibodies on HIV-1 p24 Ag⁺ infected cells and uninfected CD4⁺ T cells. The HeLa cell line was used as a positive control for MICA and MICB expression. MFI = mean fluorescent intensity of antibody used for staining the cells. Data are representative of 3 separate studies.