NK cells from HIV-infected patients had lower perforin expression that was restored by IL-12 treatment. (A) NK cells from healthy donors and HIV-infected patients on ART were freshly isolated, made permeable, labeled with antiperforin antibody, and analyzed by flow cytometry. (B) NK cells from HIV-infected patients on ART were freshly isolated, treated with IL-12 or not treated, made permeable, labeled with antiperforin antibody, and analyzed by flow cytometry. (C) NK cells from healthy donors were freshly isolated, treated with IL-12 or not treated, made permeable, labeled with antiperforin antibody, and analyzed by flow cytometry. Data in panels A to C are from one of 5 representative experiments. (D) Mean fluorescence intensity of perforin labeling in IL-12-treated NK cells. Data shown are the mean from n = 5 independent healthy controls and n = 5 independent HIV-infected patients. Data are the mean ± standard error of the mean. *, P < 0.05; ns, not significant.