Beutler group identified TLR7 along with TLR8 and TLR9 within an established genomic database in the year 2000 (Du et al. 2000). TLR7 was evolved from common ancestral gene about 150 million years ago and was found to be X linked (Du et al. 2000). In 2002, synthetic chemical imiquimod was reported to be sense by TLR7, which was characterized as another antiviral TLR (Hemmi et al. 2002). Later in 2004, two groups independently identified TLR7 as a sensor of single-stranded viral RNA (Diebold et al. 2004; Heil et al. 2004). There are several synthetic compounds belonging to imidazoquinoline family, which have been identified as TLR7 and/or TLR8 agonists (Diebold et al. 2004). Among these agonists, the lead compound imiquimod exerts strong antiviral and antitumoral activities and is being marketed for the treatment of external genital warts caused by human papillomavirus (Wolf et al. 2003).
Pattern recognition receptors are...
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