Although sharing a similar structure, genomic localization, and involvement in RNA sensing, TLR7 and TLR8 are found in distinct immune cells (Hornung et al. 2002). This selective expression correlates with distinct biological functionality and production of type I IFNs (Gorden et al. 2005; Cervantes et al. 2011).
The initial observations that TLR8-deficient mice did not show any defect in nucleic acid detection, due to a lack of response to imidazoquinolines and RNA (Heil et al. 2004; Jurk et al. 2002), lead to a relative lack of interest in this particular endosomal TLR. Very recently it has been reported that overexpression of mTLR8 is required for the activation of transcription factor NF-κB and the production of TNF-α (Li et al. 2016). These results demonstrate that mTLR8 is indeed functional and does play a role in the activation of innate immune responses.
Structural Features of the TLR8 Ligand Recognition Domain
- Cervantes JL, Dunham-Ems SM, La Vake CJ, Petzke MM, Sahay B, Sellati TJ, et al. Phagosomal signaling by Borrelia burgdorferi in human monocytes involves Toll-like receptor (TLR) 2 and TLR8 cooperativity and TLR8-mediated induction of IFN-beta. Proc Natl Acad Sci USA. 2011;108(9):3683–8.PubMedPubMedCentralCrossRefGoogle Scholar
- Gu L, Zhou J, Tan J, Yang J, Shen T, Jiang H, et al. Association of TLR8 gene rs3764880 polymorphisms with susceptibility and lipid metabolism- and inflammation response-related quantitative traits of ischemic stroke in southern Chinese Han male population. J Neurol Sci. 2016;370:94–9.PubMedCrossRefGoogle Scholar
- Hornung V, Rothenfusser S, Britsch S, Krug A, Jahrsdorfer B, Giese T, et al. Quantitative expression of toll-like receptor 1-10 mRNA in cellular subsets of human peripheral blood mononuclear cells and sensitivity to CpG oligodeoxynucleotides. J Immunol. 2002;168(9):4531–7.PubMedCrossRefGoogle Scholar