IL-4 promotes Th2 differentiation of NFAT1^−/− IL-4^−/− T cells.

(A) IL-4 treatment up-regulates mRNAs encoding Th2 cytokines and down-regulates IFN-γ mRNA in both NFAT1^−/−IL-4^−/− (▨) and NFAT1^+/+IL-4^−/− (▪) cells. CD4⁺ T cells from NFAT1^+/+ IL-4^−/− and NFAT1^−/−IL-4^−/− mice were cultured for 4 days with anti-CD3 and IL-2 in the presence of IL-4 (0-1000 U/mL), rested for 48 hours, and restimulated with anti-CD3. Six hours after restimulation, total cellular RNA was isolated and analyzed by RNase protection assay for transcript levels of the indicated cytokines. (B) IL-4 treatment up-regulates IL-5 production and down-regulates IFN-γ production in both NFAT1^−/− IL-4^−/− and NFAT1^+/+ IL-4^−/− cells. NFAT1^+/+IL-4^−/− and NFAT1^−/− IL-4^−/−CD4⁺ T cells were cultured as in panel A. Supernatants were collected 24 hours after restimulation, and levels of IFN-γ and IL-5 were determined by ELISA. Values are expressed as the means ± SEM of 3 independent experiments.