IFNG and infection: Furthermore, T-bet, a transcription factor that promotes IFN-γ expression by CD4+ T cells and can interact with Bhlhe40 in NKT cells to regulate IFN-γ expression (27), showed no significant difference in expression between WT and Bhlhe40−/− splenocytes or splenic CD4+ T cells after infection (Fig. S1B and C), although the expression of Tbx21 was increased in the spleen of Bhlhe40−/− mice 7 days after infection compared to day 5.