Porphyromonas gingivalis lipopolysaccharide promotes T-hel per17 cell differentiation by upregulating Delta-like ligand 4 expression on CD14+ monocytes

Backgroud To investigate the effect and mechanism of Porphyromonas gingivalis ( P. gingivalis ) lipopolysaccharide (LPS) on Th17 cell differentiation mediated by CD14 + monocytes.Methods P . gingivalis LPS-activated CD14 + monocytes were co-cultured with CD4 + T cells in different cell ratios. An indirect co-culture system was also established using transwell chambers. Furthermore, anti- Delta-like ligand 4 (Dll-4) antibody was used to investigate the role of Dll-4 in Th17 cell response. The mRNA expression was analyzed using quantitative reverse transcription-polymerase chain reaction, and secreted cytokines in culture supernatant were detected using enzyme-linked immunosorbent assay. Flow cytometry was used to determine the frequencies of Th17 cells. IL-17 protein expression levels were determined using western blotting assay.Results P. gingivalis LPS increased the expressions of interleukin (IL)-1 β , IL-6, IL-23 and transforming growth factor (TGF)- β in CD14 + monocytes. Th17 cell frequency upregulated, which is not solely cytokine-dependent but rather requires cell-cell contact with activated monocytes, particularly in the 1:10 cell ratio. Furthermore, P . gingivalis LPS increased t he expression of Dll-4 on CD14 + monocytes, whereas the anti- Dll-4 a ntibody decreased the response of Th17 cells. The results suggest that P . gingivalis LPS enhances Th17 cell response via Dll-4 upregulation on CD14 + monocytes.