Objective:To investigate the effects of E.coli lipopolysaccharide(LPS) stimulus on the synthesis of TLR4 protein and its mRNA expression in human dental pulp cells(HDPCs), and to explore the roles of TLR4 on the activation of HDPCs induced by LPS. Methods:The expressions of TLR4 mRNA and the synthesis of TLR4 protein in HDPCs induced by LPS were detected by real-time fluorescence quantitative RT-PCR(FQ RT-PCR) and immunofluorescence technique.IL-1? concentrations in the supernatant of cultured HDPCs pretreated with TLR4 antibody were assayed with ELISA. Results: The expressions of TLR4 could not be detected in normal HDPCs.After being stimulated with 1?10-4 g/L LPS for 6,12 or 24 h, immunostaining showed that TLR4 was expressed in cytomembrane and cytoplasm of HDPCs,while in nucleus the expressions were negative. FQ RT-PCR showed their expressions significantly increased after being stimulated with LPS (P