SUPPLEMENTAL EXPERIMENTAL PROCEDURES Mice

mice. SMARTA1 TCR-transgenic (tg) mice (Oxenius et al., 1998), which express a TCR specific for the LCMV glycoprotein epitope GP61–80, were crossed to Thy1.1+ B6.PL mice, Ifngr1-/- mice, Ifnar1-/- mice, and Tbx21-/- mice to generate TCRtg mice on the respective mutant backgrounds. T cell activation and differentiation Naive MACS-sorted LCMV-TCRtg CD4+CD62LhiCD25- T cells from spleens and lymph nodes were cultured in RPMI 1640 supplemented with 10 % (vol/vol) FCS (Gibco), L-glutamine (2 µM; Gibco), penicillin (100 U/ml; Gibco), streptomycin (100 µg/ml; Gibco), and β-mercaptoethanol (50 nM; Sigma) in the presence of APCs and 1 µg/ml GP64–80 peptide (Neosystem). For Th1 differentiation, 3 ng/ml IL-12 (R&D Systems) and 10 µg/ml anti-IL-4 (11B11) were added. For Th2 differentiation, 30 ng/ml IL-4 (Sigma-Aldrich) plus 10 µg/ml anti-IL-12 (C17.8) and 10 µg/ml anti-IFN-γ (AN18.17.24) were used, as described previously (Lohning et al., 2008). For in vitro conversion experiments, IFN-α and IFN-β (PBL InterferonSource) were used at 1,000 U/ml. Cell cultures were split on days 2 and 4. On day 6, cells were reactivate