Inhibition of cytokine-mediated STAT1 activation by SOCS-1 contributes to overproduction of IFN-λ during IAV infection.

<p>(<b>A</b>) A549 cells expressing SOCS-1, empty vector (EV) or shRNAs targeting SOCS-1 or luciferase (Luc) were treated with or without IL-29 (50 ng/ml) for 45 min. Cell lysates were analyzed by Western blotting using indicated antibodies. (<b>B, C</b>) Luc or SOCS-1 knockdown A549 cells were infected without (B) or with (C) WSN virus for 15 h and then treated with IL-29 for indicated time. Shown are immunoblots of the cell lysates probed with indicated antibodies. (<b>D, E</b>) SOCS-1-ablated or control A549 cells were infected with or without WSN virus for 15 h. Subsequently, IL-29 levels in the supernatants from the cell culture were examined by ELISA. IL-29 levels produced by infected control cells were set to 100%. Plotted are the average results from three independent experiments and the error bars represent the S.E. (D). mRNA levels of OAS-2, Mx1, IL-28A/B, and IL-29 were examined by RT-PCR (E). (<b>F</b>) Levels of these mRNAs in (E) were quantitated by densitometry, and normalized to GAPDH levels as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003845#ppat-1003845-g002" target="_blank">Figure 2D</a>. mRNA level in infected control cells is 100. Plotted are the average results from three independent experiments. The error bars represent the S.E. Statistical significance of change was determined by Student's t-test (*P<0.05).