TLR9 and viral infectious disease: For example: the recognition of TLR9 as the cellular receptor for bacterial DNA [69]; the critical role of MyD88 in interleukin signalling [70]; the in vivo role of TLR2 [71]; the identification of the TLR adaptor protein TRIF [72]; the importance of NAIP5 for resistance to Legionella pneumophila infection [60]; and the importance of TLR9 in the sensing of unmethylated DNA as a protection against viral infection [73].