Examination of production of 3 different cytokines by EBV-specific CTLs using LCLs as natural ligand stimulators or phorbol myristate acetate and ionomycin as chemical stimulators. (A and D) Unstimulated CTLs; (B and E) CTLs stimulated with autologous LCL at a responder stimulator ratio of 1; and (C and F) CTLs stimulated with phorbol myristate acetate and ionomycin. After fixation and permeabilization, the cells were stained for CD8, IFNγ, and IL-4 (A through C) or IL-13 (D through F). CD8⁺ cells were gated and analyzed using flow cytometry.