Correlation of IFN-γ–producing T cells by Elispot and intracellular FACS-staining.

(A) Number of tetramer⁺ (percentage of CD8⁺ T cells, solid line) and IFN-γ–producing T cells (per 10⁶CD8⁺ T cells, dashed line), as assessed by Elispot assay, are shown in the course of HIV-1 infection for RAK-specific T cells of one AIDS-NHL patient (NHL0308, left panel) and one LTA individual (LTA0036, right panel). (●) indicates tetramer; (○), IFN-γ. (B) Intracellular IFN-γ staining, as described in “Patients, materials, and methods,” after stimulation with RAK peptide is shown at an early time point in HIV-1 infection for the AIDS-NHL patient and an early and late time point for the LTA individual, revealing the percentage of IFN-γ–producing CD8⁺ T cells (upper right quadrant). (C) Combination of tetramer and intracellular IFN-γ staining after peptide stimulation is shown at an early time point for the AIDS-NHL patient, revealing the percentage tetramer⁺ (2.3%, upper left quadrant) T cells, IFN-γ⁺ (0.21%, upper and lower right quadrant) T cells, and proportion of IFN-γ⁺tetramer⁺ CD8⁺ T cells (9%, gray box).