Abstract： Objective To compare the ability of the polysaccharide from various Porphyromonas gingivalis(Pg) type and clinical strains in inducing THP-1 cells to produce cytokines interleukin (IL)-1 β,IL-8,and tumor necrosis factor (TNF)-or,in order to analyze the immunogenicity of Pg polysaccharide components and the virulence-associated factors of this periodontal pathogen.Methods The bacterial polysaccharide was extracted from high virulent Pg strains,W83,SJD2,SJD12 and low virulent Pg,ATCC33277,SJD4,SJD5,and SJD11 by phenol-water extraction.The extracted polysaccharide was used to stimulate the THP-1 cells with different simulation periods and doses.The level of the cytokines,including IL-1 β,IL-8 and TNF-α in the cell culture suspension was measured by enzyme-linked immunosorbent assay (ELISA).Results The polysaccharide extraction of Pg strains was composed of lipopolysaccharide (LPS) and capsular polysaccharide.The secretion of IL-1 β,IL-8 and TNF-α,produced by the THP-1 cells showed in a time-and dose-dependent manner in the medium containing 10％ fetal bovine serum.The level of these cytokines of the high virulent strains was higher than that of the low virulent strains in medium containing 1％ fetal bovine serum.Four hours after stimulation with polysaccharide extracted from high virulent strains,the levels of IL-1β,IL-8,and TNF-α in the cell suspension were (1 639 ± 497),(1 648 ± 513) and (140 ±48) μg/L,respectively,whereas for low virulent strains,the levels of IL-1β,IL-8,and TNF-o were (773 ±382),(892 ± 400) and (67 ± 33) μg/L,respectively.Conclusions Polysaccharide extracted from Pg could induced the THP-1 cells to secrete the cytokines of IL-1β,IL-8 and TNF-α.The level of the cytokines produced by the THP-1 cells associates with the bacterial virulent properties.