Cytokine-induced IFN-γ secretion is JAK3 and p38-MAPK dependent. CD45RA⁻ memory Th cells were preincubated for 45 minutes with different concentrations of JAK3 inhibitor I (A), PD98059 (B), SB202190 (C), or CsA (D) and subsequently stimulated for 36 hours with the cytokine cocktail or for 12 hours with αCD3 + αCD28. IFN-γ expression was analyzed intracellularly by FACS. Frequencies of IFN-γ⁺ Th cells in the absence of an inhibitor were set to 100%. One representative experiment of 3 (B,D) or 5 (A,C) is shown.