From Wikipedia, the free encyclopedia
Jump to: navigation, search
Aliases TLR9, CD289, toll like receptor 9
External IDs OMIM: 605474 MGI: 1932389 HomoloGene: 68126 GeneCards: TLR9
Targeted by Drug
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 3: 52.22 – 52.23 Mb Chr 9: 106.22 – 106.23 Mb
PubMed search [2] [3]
View/Edit Human View/Edit Mouse

Toll-like receptor 9 is a protein that in humans is encoded by the TLR9 gene.[4] TLR9 has also been designated as CD289 (cluster of differentiation 289). It is a member of the toll-like receptor (TLR) family.


The TLR family plays a fundamental role in pathogen recognition and activation of innate immunity. TLRs are named for the high degree of conservation in structure and function seen between mammalian TLRs and the Drosophila transmembrane protein Toll. TLRs are transmembrane proteins, expressed on the cell surface and the endocytic compartment and recognize pathogen-associated molecular patterns (PAMPs) that are expressed on infectious agents and initiate signalling to induce production of cytokines necessary for the innate immunity and subsequent adaptive immunity. The various TLRs exhibit different patterns of expression.[5]

This gene is preferentially expressed in immune cell rich tissues, such as spleen, lymph node, bone marrow and peripheral blood leukocytes. Studies in mice and humans indicate that this receptor mediates cellular response to unmethylated CpG dinucleotides in bacterial DNA to mount an innate immune response.[5]

TLR9 recognizes unmethylated CpG sequences in DNA molecules. CpG sites are relatively rare (~1%) on vertebrate genomes in comparison to bacterial genomes or viral DNA. TLR9 is expressed by numerous cells of the immune system such as B lymphocytes, monocytes, natural killer (NK) cells, and plasmacytoid dendritic cells. TLR9 is expressed intracellularly, within the endosomal compartments and functions to alert the immune system of viral and bacterial infections by binding to DNA rich in CpG motifs. TLR9 signals leads to activation of the cells initiating pro-inflammatory reactions that result in the production of cytokines such as type-I interferon and IL-12.

As an immunotherapy target[edit]

There are new immunomodulatory treatments undergoing testing which involve the administration of artificial DNA oligonucleotides containing the CpG motif. CpG DNA has applications in treating allergies such as asthma,[6] immunostimulation against cancer,[7] immunostimulation against pathogens, and as adjuvants in vaccines.[8]

TLR9 agonists[edit]

  • lefitolimod (MGN1703) has started clinical trials to treat (in combination with ipilimumab) patients with advanced solid malignancies.[9]

Protein interactions[edit]


  1. ^ "Drugs that physically interact with Toll like receptor 9 view/edit references on wikidata". 
  2. ^ "Human PubMed Reference:". 
  3. ^ "Mouse PubMed Reference:". 
  4. ^ Du X, Poltorak A, Wei Y, Beutler B (Dec 2000). "Three novel mammalian toll-like receptors: gene structure, expression, and evolution". Eur Cytokine Netw. 11 (3): 362–71. PMID 11022119. 
  5. ^ a b "Entrez Gene: TLR9 toll-like receptor 9". 
  6. ^ Kline JN (July 2007). "Eat dirt: CpG DNA and immunomodulation of asthma". Proc Am Thorac Soc. 4 (3): 283–8. doi:10.1513/pats.200701-019AW. PMC 2647631Freely accessible. PMID 17607014. 
  7. ^ Thompson JA, Kuzel T, Bukowski R, Masciari F, Schmalbach T (July 2004). "Phase Ib trial of a targeted TLR9 CpG immunomodulator (CPG 7909) in advanced renal cell carcinoma (RCC)". Journal of Clinical Oncology, 2004 ASCO Annual Meeting Proceedings (Post-Meeting Edition). 22 (14S). 
  8. ^ Klinman DM (2006). "Adjuvant activity of CpG oligodeoxynucleotides". Int. Rev. Immunol. 25 (3-4): 135–54. doi:10.1080/08830180600743057. PMID 16818369. 
  9. ^ MOLOGEN AG: First patient recruited in combination study with lefitolimod and Yervoy. July 2016
  10. ^ Chuang TH, Ulevitch RJ (May 2004). "Triad3A, an E3 ubiquitin-protein ligase regulating Toll-like receptors". Nat. Immunol. 5 (5): 495–502. doi:10.1038/ni1066. PMID 15107846. 

Further reading[edit]

External links[edit]

This article incorporates text from the United States National Library of Medicine, which is in the public domain.