Preventing the interaction between NK-cell coreceptors and their ligands on HIV-infected cells decreases NK-cell killing of the targets. (A,B) CD4⁻/HIV-1 p24 Ag⁺ HIV-1_SF128A–infected or (C) HIV-1_SF162–infected primary T cells were exposed to autologous NK cells treated in the absence (isotype control) or presence of anti-2B4 or NTB-A blocking monoclonal antibodies in a 4-hour cytotoxicity assay. Panels A through C represent 3 separate experiments involving 3 different donors (*, P < .05; t test). Error bars represent standard deviation of the mean.