2′-O-Methyl-guanosine RNA fragments antagonize TLR7 and TLR8 to limit autoimmunity

Recognition of RNA fragments by Toll-like receptor 7 (TLR7) and TLR8 helps to initiate the innate immune response against pathogens. An outstanding question is why RNA fragments generated during clearance of apoptotic cells fail to activate TLR7 and TLR8 signaling. Here we show that select 2'-O-methyl (2'-OMe) guanosine RNA fragments, including those derived from host RNAs, function as potent TLR7 and TLR8 antagonists and reduce TLR7 sensing in vivo. Mechanistically, these fragments bind to an antagonistic site on these proteins via their 5'-end 2'-OMe guanosine. These findings indicate that host RNAs evade detection because abundant ribosomal 2'-OMe-modified fragments naturally antagonize TLR7 and TLR8.…