Down-Regulation of TLR9 Expression Affects the Maturation and Function of Murine Bone Marrow-Derived Dendritic Cells Induced by CpG

Abstract

Toll-like receptor 9 (TLR9) is expressed intracellularly by dendritic cells (DCs) and specifically recognizes unmethylated CpG motif. Recognition of TLR9 to CpG DNA can induce DC maturation followed by the subsequent immune responses. Here, RNA interference (RNAi) was used to identify the effect of CpG DNA signaling on DC function. The results showed that transfection of DCs with siRNA specific for TLR9 gene significantly down-regulated TLR9 expression. Immature DCs transfected with TLR9 siRNA did not differentiate into mature DCs with exposure to CpG. TLR9 siRNA-treated DCs expressed low levels of MHC II and CD40 without reducing endocytosis. Furthermore, TLR9 siRNA-transfected DCs exhibited a decreased allostimulatory capacity in a lymphocyte proliferation assay and attenuated Th1 responses by decreasing IL-12p70 production. Our findings indicate that siRNA in silencing TLR9 gene in DCs may offer a potential tool to study the TLR9-CpG pathway.

Therapeutic Targeting of TLR9 Inhibits Cell Growth and Induces Apoptosis in Neuroblastoma

“…This finding is consistent with a recent report in which investigators, by using RNA interference, downregulated only partially the expression of TLR9 in dendritic cells. Nevertheless, such downregulation was sufficient to abrogate the effects of CpG ODNs in the induction of dendritic cells maturation (43). In contrast, we observed that all NB-cell lines transfected with siRNA against TLR9 retained the ability to respond to CpG, undergoing apoptosis.…”

Toll-like receptors in acute liver injury and regeneration

“…In human, pDCs express TLR1, 7 and 9, while other DC subsets express all other TLRs but not TLR9 [32]. In the mouse liver, TLR2, TLR4, TLR7 and TLR9 are found on both cDCs and pDCs, but TLR3 is not expressed on pDCs [33,34]. Hepatic cDCs express higher levels of TLR2 and TLR4 than splenic cDCs.…”

Interferon Regulation Factor‐3 is a Critical Regulator of the Mature of Dendritic Cells from Mice

“…RNAi has been used to inhibit IRF‐3 expression, which appears to be more attractive due to several distinct advantages with extremely efficient and specific characters . Moreover, this technique is not difficult to perform and its effect can be confirmed within days using simple detection systems, such as real‐time RT‐PCR and Western blot.…”