IFN-γ is specifically controlled by IRF4. A, HuT-102, ED40515(−), and MT-2 cells were transfected with siRNAs against IRF4, c-Rel, RORC, and Luc. At 60 h post-transfection, IFN-γ mRNA expression was examined by RT-PCR. B, HuT-102 cells were transfected with siRNAs against IRF4 and T-bet. IRF4, T-bet, IFN-γ, and IL-17A mRNAs were quantified by real-time RT-PCR.