Figure 4.

(A) Kinetics and requirements of TCR- and cytokine-induced IFN-γ production. CFSE-labeled CD4⁺ memory T cells were stimulated for the indicated times with either anti-CD3 and anti-CD28 antibodies (squares), or with TNF-α, IL-12, and IL-18 in the absence (circles) or presence (triangles) of IL-7 and IL-15. IFN-γ production was analyzed by intracellular staining. Empty symbols indicate conditions with undivided cells, whereas filled symbols indicate conditions with dividing cells. The mean percentage of IFN-γ⁺ cells of three independent experiments is plotted. (B) Cytokine-stimulated CXCR3⁺ T_CM cells lacking IFN-γ–producing capacity become Th1 cell effector cells. Purified CFSE-labeled CXCR3⁺ T_CM and CCR4⁺ T_CM cells were stimulated with IL-7, IL-15, TNF-α, IL-12, and IL-18 for 60 h, and IFN-γ–secreting cells were purified by cell sorting. IFN-γ⁺ and IFN-γ⁻ cells were then expanded for an additional 5 d with IL-7 and IL-15, briefly stimulated with PdBu and ionomycin, and analyzed for IL-4 and IFN-γ production by intracellular staining. One representative donor out of three is shown.