Toll-like receptor 9 (TLR9)

Toll-like receptor 9 (TLR9) is a member of the toll-like receptor (TLR) family, playing a key role in the innate immune system. It recognizes unmethylated cytidine-phosphate-guanosine dinucleotides (CpG motifs) found in bacterial and viral DNA, as well as synthetic CpG oligodeoxynucleotides. Upon ligand binding, TLR9 initiates a signaling cascade involving MyD88, leading to NF-kB activation and production of pro-inflammatory cytokines and type I interferons. TLR9 is expressed primarily in immune cells like dendritic cells, macrophages, B cells, and NK cells, and can be found in endolysosomes/endosomes (eTLR9) or on the cell surface (sTLR9). It plays a role in antiviral and antitumoral responses, but its dysregulation has been implicated in autoimmune diseases. TLR9 is a therapeutic target for cancer and autoimmune disorders.

Other names

CD289

TLR9 agonists stimulate TLR9, leading to MyD88-dependent activation of NF-kB and subsequent cytokine/interferon production. TLR9 antagonists inhibit this signaling pathway.