Effect of TLR3 agonist on PKR expression and phosphorylation in NB cell lines. (A) Western blot analysis. After treatment with 50 μg/ml poly(I:C) for 24 h, NB cells were harvested and subjected to immunoblot analysis. (B) Quantification of PKR activation in NB cells after poly(I:C) treatment. The ratio of phosphorylated PKR level over total PKR level was determined and expressed as mean ± SD from triplicate experiments. *: P < 0.05.