Toll-like receptor 3: A link between toll-like receptor, interferon and viruses

Production of type I interferon (IFN-alpha/beta) by virus-infected cells is the central event in their antiviral immune responses. In mammalian cells, IFN-alpha/beta gene transcription is induced through distinct signaling pathways by viral infection or by treatment with double-stranded (ds) RNA, which is an intermediate of virus replication. Toll-like receptor 3 (TLR3) was found to recognize dsRNA and transmit signals to activate NF-kappaB and the IFN-beta promoter. Recent identification of the TLR3-adaptor protein and its downstream signaling molecules, which are involved in IFN-alpha/beta production, revealed a novel IFN-inducing pathway for an anti-viral immune response. Here, we summarize the current knowledge of TLR3-mediated immune responses.