TLR3 and infection: Sensors of dsRNA, such as toll-like receptor 3 (TLR3) in the endosome and RNA helicases retinoic acid-inducible gene protein I (RIG-I) or melanoma differentiation-associated protein 5 (MDA5) in the cytoplasm recognise dsRNA and mediate hierarchical activation of downstream signals, ultimately triggering the type I/III interferon (IFN-I/III) response, which normally defends against viruses, in the absence of infection [57–60, 62, 63].