Toll like receptors
toll like receptors
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single, membrane-spanning, non-catalytic receptors usually expressed in sentinel cells such as macrophages and dendritic cells, that recognize structurally conserved molecules derived from microbes. Once these microbes have breached physical barriers such as the skin or intestinal tract mucosa, they are recognized by TLRs, which activate immune cell responses. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12, and TLR13, though the latter 3 are not found in human. They received their name from their similarity to the protein coded by the toll gene identified in Drosophila in 1985 by Christiane Nüsslein-Volhard. The researchers were so surprised that they spontaneously shouted out in German, ' Das ist ja toll! ' which translates as 'That's great!'