Recognition of extracellular or endosomal pathogen-associated molecular patterns is mediated by transmembrane proteins known as toll-like receptors (TLRs). TLRs share a typical structural motif, the Leucine rich repeats (LRR), which give them their specific appearance and are also responsible for TLR functionality. Toll-like receptors were first discovered in "Drosophila" and trigger the synthesis and secretion of cytokines and activation of other host defense programs that are necessary for both innate or adaptive immune responses. 10 functional members of the TLR family have been described in humans so far. Studies have been conducted on TLR11 as well, and it has been shown that it recognizes flagellin and profilin-like proteins in mice. Nonetheless, TLR11 is only a pseudogene in humans without direct function or functional protein expression. Each of the TLR has been shown to interact with a specific PAMP.