Figure 2.

IL-25 promotes Th2 cell differentiation in vitro. (A) mRNA expression of IL-17RB on freshly isolated naive T cells and in vitro–generated Th1 and Th2 cells was analyzed by RT-PCR. (B) Naive T cells were stimulated with anti-CD3, anti-CD28, and IL-2 in the presence of human IgG or recombinant IL-25. After 4 d, cells were restimulated with plate-bound anti-CD3 for 24 h, and cytokine production was measured by ELISA. *, P < 0.005. (C) Naive T cells were activated as described with or without anti–IFN-γ in the presence of human IgG or recombinant IL-25. After 5 d, cells were restimulated with PMA/ionomycin, and the expression of IL-4 and IFN-γ was analyzed. Numbers within the quadrants indicate the percentage of cells stained positive for each respective cytokine. (D) Naive T cells were purified and stimulated with anti-CD3, anti-CD28, anti–IFN-γ, and IL-2 in the presence of different concentrations of IL-25 for 6 d. 50 μg/ml anti–IL-25 mAb was added to the culture containing IL-25 at 2 μg/ml. The amounts of cytokines were measured by ELISA. Data are presented as mean values + SD and are representative of at least two independent experiments. HPRT, hypoxanthine-guanine phosphoribosyltransferase.