Objective To study the effects of Treponema pallidum membrane protein Tpp17 on ac-tivation of human umbilical vein endothelial cells (HUVECs) in vitro and to understand its role in the immu-nopathogenesis of syphilis .Methods HUVECs were co-cultured with recombinant protein Tpp 17.Then the expressions of TNF-α, MCP-1, ICAM-1 and E-selectin at mRNA and protein levels in supernatants were re-spectively detected by enzyme-linked immunosobent assay ( ELISA ) and fluorescent real-time quantitative PCR.The adhesive ability of THP-1 cells was observed by fluorescence microscopy after co-cultured pretrea-ted HUVECs with recombinant protein Tpp 17 with Calcein-AM labeled THP-1.Pretreated HUVECs were cultured in the lower chamber of Transwell with recombinant protein Tpp 17 and monocytic THP-1 cells were cultured in the upper chamber of Transwell .After that, the migration of monocytic THP-1 cells was evalua-ted by using fluorescence microscopy .Results Compared with the blank control group , the expression of TNF-α, ICAM-1, E-selectin, especially the MCP-1, were enhanced by recombinant protein Tpp 17 of Trepo-nema pallidum.Moreover, Tpp17 improved the adhesive ability and migration of monocytic THP-1 cells, es-pecially the latter.Conclusion Treponema pallidum membrane protein Tpp17 might play a certain role in the immunopathogenesis of syphilis by enhancing the expression of TNF-α, MCP-1, ICAM-1 and E-selectin, and by promoting the adherence ability and migration of monocytic THP-1 cells.