To date,at least ten members of the Toll family have been identified. TLRs recognize molecular patterns associated with microbial pathogens and induce antimicrobial immune response. TLR3 recognizes double-stranded (ds) RNA,induces the activation of NF-kB,through MyD88-dependent and -independent pathways,and the production of type I interferons (IFNs). Similar to several other members of the TLR family,TLR3 has been reported to be expressed at a very low level on the surface of human fibroblast cell lines.