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  • Double-stranded RNAs from t...
    Aksoy, Ezra; Zouain, Claudia S.; Vanhoutte, François; Fontaine, Josette; Pavelka, Norman; Thieblemont, Nathalie; Willems, Fabienne; Ricciardi-Castagnoli, Paola; Goldman, Michel; Capron, Monique; Ryffel, Bernard; Trottein, François

    Journal of biological chemistry/˜The œJournal of biological chemistry, 01/2005, Letnik: 280, Številka: 1
    Journal Article

    Stimulation of dendritic cells (DCs) by the egg stage of the helminth parasite Schistosoma mansoni activates a signaling pathway resulting in type I interferon (IFN) and IFN-stimulated gene (ISG) expression. Here, we demonstrate that S. mansoni eggs disjointedly activate myeloid differentiation factor 88 (MyD88)-dependent and MyD88-independent pathways in DCs. Inflammatory cytokine expression and NF-κB activation in DCs from MyD88-deficient mice were impaired, whereas signaling transducer activator of transcription (STAT) 1(Tyr701) phosphorylation and ISG expression were intact in MyD88 or Toll-like receptor (TLR)4-deficient counterparts. Accordingly, we analyzed distinct TLR members for their ability to respond to schistosome eggs and established that TLR3 resulted in the activation of NF-κB and the positive regulatory domain III-I site from IFN-β promoter. Unexpectedly, egg-derived RNA possessed RNase A-resistant and RNase III-sensitive structures capable of triggering TLR3 activation, suggesting the involvement of double-stranded (ds) structures. Moreover, DCs from TLR3-deficient mice displayed a complete loss of signaling transducer activator of transcription 1 phosphorylation and ISG expression in response to egg-derived dsRNA. Finally, TLR3-deficient DCs showed a reduced response to schistosome eggs relative to wild-type cells. Collectively, our data suggest for the first time that dsRNA from a non-viral pathogen may act as an inducer of the innate immune system through TLR3.