Dendritic cells (DCs) play a critical role in activation of T cells as well as shaping immune responses. DCs express a pattern of Toll-like receptors (TLRs) to recognize invading pathogens and to initiate specific immune responses. In this study, we investigated the effect of Porphyromonas gingivalis fimbriae on the phenotype and function of human peripheral blood DCs (PBDCs) in comparison to TLR2 and TLR4 ligand, peptidoglycan (PGN) from Staphylococcus aureus and Escherichia coli O55:B5 LPS, respectively. P. gingivalis fimbriae and PGN preferentially upregulated CD14 and CD16 expression on immature PBDCs (CD14-CD16-), although E. coli LPS did not alter the expression of these molecules. Fimbriae-stimulated DCs also exhibited a different profile of cytokine production and surface molecule expression as compared with E. coli LPS-stimulated DCs. Pretreatment of PBDCs with anti-TLR2 monoclonal antibody (mAb), but not with anti-TLR4 mAb, abrogated the upregulation of CD14 and CD16 on fimbriae and PGN-treated DCs. These results indicate that different TLR signaling affects the mature DC phenotype and function and is thus crucial to the regulation of immunity to the pathogen.
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