Toll-Like Receptors or TLRs

Toll like receptors (TLR) are highly conserved throughout evolution and have been implicated in the innate defense to many pathogens. In mammals, TLR identified as type I transmembrane signaling receptors with pattern recognition capabilities have been implicated in the innate host defense to pathogens.

Image: Toll-Like Receptor 4 (TLR4 or CD284) staining of immersion fixed paraffin-embedded sections of human prostate at 10 µg/mL overnight at 4 °C. Before incubation with the primary antibody tissue was subjected to heat-induced epitope retrieval using Antigen Retrieval Reagent.  Tissue was stained using the Anti-Goat HRP-DAB. (brown) and counterstained with hematoxylin (blue)

These microbial molecular markers may be composed of proteins, carbohydrates, lipids, nucleic acids and/or combinations thereof. Individual TLRs recognize distinct pathogen-associated PAMPs, initiating signaling cascades that promote the immune response. Structurally, TLRs are type I transmembrane receptors that possess varying numbers of extracellular N-terminal leucine-rich repeat (LRR) motifs, followed by a cysteine-rich region, a TM domain, and an intracellular Toll/IL-1 R (TIR) motif.