Toll9 fromBombyx morifunctions as a pattern recognition receptor that shares features with Toll-like receptor 4 from mammals

Significance Toll/Toll-like receptors are key regulators of the innate immune system in both invertebrates and vertebrates. However, while mammalian Toll-like receptors function as pattern recognition receptors that directly bind microbe-associated ligands, arthropod Tolls are generally thought to be activated by Spätzle cytokines. Here, we show that Toll9 from the silkmothBombyx mori functions as a pattern recognition receptor that binds lipopolysaccharide. Our results provide a link for both structural and functional conservation between an insect Toll and a mammalian Toll-like receptor family member.