TLR4 and influenza: TLR3 are known to identify viruses like RSV and HRV, whereas TLR4 recognizes bacteria like Haemophilius influenza. During experimental conditions poly(I:C) and LPS, ligands for TLR3 and TLR4, can be used to mimic the innate immune effects of viruses (i.e. RSV/HRV) and bacteria (i.e. Haemophilius influenza), respectively.