TLR3 activation induces IFN-λ1 expression. (A) Effect of poly I:C on IFN-λ1 mRNA expression. Huh7 cells were stimulated with poly I:C at the indicated concentrations for 24 h. (B) Effect of poly I:C on IFN-λ1 protein production. Huh7 cells were stimulated with poly I:C at the indicated concentrations for 48 h. SN was collected from the cell cultures for ELISA to measure the protein levels of IFN-λ1. (C, D) Blocking TLR3 signaling compromises poly I:C-induced IFN-λ1 expression. Huh7 (C) or Huh7.5 (D) cells were pretreated with or without Bafilomycin A1 (100 nM) for 1 h prior to poly I:C stimulation (24 h). Total RNA extracted from cells was subjected to the real time RT-PCR for the mRNA levels of IFN-λ1 and GAPDH. The data are expressed IFN-λ1 mRNA levels relative (fold) to the control (vehicle only, which defined as 1). The results shown are mean ± SD of triplicate cultures, representative of three experiments (poly I:C stimulated Huh7 cell vs vehicle only, **P<0.01, *P<0.05).