Toll-like receptor Expression in Human Gingival Resident Cells and Tissue

Objectives: Toll-like receptors (TLRs) are type I transmembrane proteins essential for innate immunity. They recognize various highly conserved structures that share pathogen-associated molecular patterns. Among the ten TLRs in human, TLR-1, -2, -4, -5 and -9 mainly react to bacteria, TLR-6 specially recognizes mycoplasma, TLR-3, -7 and -8 recognize viruses, and the functional ligand of TLR-10 is unknown. In this study, we examined the expression of TLRs in human gingiva. Methods: Human gingival tissue (HGT) biopsies were obtained from orthodontically extracted teeth. Primary human gingival keratinocytes (HGK) and fibroblasts (HGF) were cultured. Total RNA of HGK (n=5), HGF (n=5), and HGT (n=5) were extracted and analyzed by Reverse Transcription PCR using specific TLR primer sets. Healthy and inflamed HGT were examined by immunohistochemistry of TLR-5 and -6. Results: mRNA of TLR-1 to -6 were detected in HGK, HGF and HGT. TLR-7， -8 and -10 were absent in HGK and HGF but were present in HGT. TLR-9 was not expressed in any of the HGK, HGF or HGT groups. Immunohistochemical expression of TLR-5 and -6 was detected in both healthy and inflamed HGT, mainly in HGK, HGF and immunocytes, but the expression was greater in inflamed groups than in healthy groups. Conclusions: Results from this study show TLR-5 and -6 are possibly more involved in gingival innate immunity compared with TLR-1 to -4. TLR-7， -8 and -10 in gingiva may be expressed by cells other than HGK and HGF. TLR-9 did not appear to be expressed in human gingiva.