Cytokine-induced IFN-γ secretion is restricted to CCR7⁻CCR5⁺IL-18Rα⁺ effector-memory Th cells coexpressing functional IL-12 receptors. (A) Correlation of intracellular IFN-γ expression with CD45RO expression in Th cells after 36 hours of stimulation with the cytokine cocktail. Shown is 1 experiment of 3. (B) Purified CCR7⁺ and CCR7⁻ Th cells were stimulated for 36 hours with the cytokine cocktail or for 12 hours with αCD3 + αCD28 and assessed intracellularly for IFN-γ. One representative experiment of 3 is shown. (C) Assessment of IL-18Rα–expressing memory Th cells within PBMCs and CCR5- and CCR7-expressing cells within the IL-18Rα⁺ Th cell population. One experiment of 5 is shown. (D) IL-18Rα⁺ and IL-18Rα⁻ Th cells were analyzed intracellularly for IFN-γ after stimulation for 36 hours with the cytokine cocktail or IL-12 + IL-18 or for 12 hours with αCD3 + αCD28. One experiment of 5 is shown. (E) Detection of phosphorylated STAT4 by immunoblotting in IL-18Rα⁺ and IL-18R⁻ Th cells after 1 hour of stimulation with IL-12 or with the cytokine cocktail. One experiment of 3 is shown. (F) Detection of phosphorylated STAT5 by immunoblotting in IL-18Rα⁺ and IL-18R⁻ Th cells after 1 hour of stimulation with IL-15. One representative experiment of 2 is shown. (G) Cytokine-induced IFN-γ secretion in a CMVpp65-specific Th1-cell line. CMVpp65-specific Th1 cells were restimulated for 12 hours with the indicated stimuli and assessed intracellularly for IFN-γ expression. One of 2 independent experiments is shown.