PI3K, CN, and NFAT control OX40-mediated IL-4 and Th2 differentiation. Naïve CD4 T cells from wild-type OT-II mice were stimulated with 0.1 μM Ag/APCs as in Fig. 1. After 12 h of activation, LY (PI3K inhibitor), cyclosporin A (CsA) (CN inhibitor) (A and B), VIVIT peptide (NFAT inhibitor), VEET control peptide (C and D), or DMSO were added. T cells were harvested at 36 h to measure IL-4 mRNA (A and C) and at day 7 to measure IL-4 recall responses after Ag restimulation as in Fig. 1 (B and D).