In contrast to cellular RNA, influenza viral RNA carries a triphosphate group at its 59 terminus that was previously shown to be a major pathogen pattern that triggers cellular signaling [46] . To verify that indeed the viral 59 triphosphate RNA in the pool of RNAs from infected cells is the major trigger for induction of SOCS-3 expression, RNA from infected or uninfected cells was treated with phosphatase to remove the 59 triphosphate termini prior to stimulation of A549 cells ( Figure 5E and 5F). The dephosphorylated viral RNA was only poorly capable to induce SOCS-3 ( Figure 5E ) or IFNb ( Figure 5F ) mRNA expression. In addition, poly(I:C) was transfected to mimic action of double-stranded (ds) RNA ( Figure 5E and 5F, right bars). However, the dsRNA analog showed surprisingly little effects on SOCS-3 and IFNb mRNA induction.