FunctionKey component of innate and adaptive immunity. TLRs (Toll-like receptors) control host immune response against pathogens through recognition of molecular patterns specific of microorganisms. TLR9 is a nucleotide-sensing TLR which is activated by unmethylated cytidine-phosphate-guanosine (CpG) dinucleotides. Acts via MYD88 and TRAF6, leading to NF-kappa-B activation, cytokine secretion and the inflammatory response.
Tissue specificityHighly expressed in spleen, lymph node, tonsil and peripheral blood leukocytes, especially in plasmacytoid pre-dendritic cells. Levels are much lower in monocytes and CD11c+ immature dendritic cells. Also detected in lung and liver.
Sequence similaritiesBelongs to the Toll-like receptor family. Contains 26 LRR (leucine-rich) repeats. Contains 1 TIR domain.
Cellular localizationEndoplasmic reticulum membrane. Endosome. Lysosome. Cytoplasmic vesicle > phagosome. Relocalizes from endoplasmic reticulum to endosome and lysosome upon stimulation with agonist.