AIM:To determine the biological activity of Helicobacter pylori(H pylori) lipopolysaccharide (H-LPS) and understandpathological correlation between H-LPS and human chronicgastritis and peptic ulcer.METHODS:H-LPS of a clinical Hpyloristrain and LPS ofEscherichia coli strain O55:B5 (E-LPS) were extracted byphenol-water method.Biological activities of H-LPS andE-LPS were detected by limulus lysate assay,pyrogen assay,blood pressure test and PBMC induction test in rabbits,cytotoxicity test in NIH 3T3 fibroblast cells and lethalitytest in NIH mice.By using self-prepared rabbit anti-H-LPSserum as the first antibody and commercial HRP-labeledsheep anti-rabbit sera as the second antibody,H-LPS inbiopsy specimens from 126 patients with chronic gastritis(68 cases) or gastric ulcer (58 cases) were examined byimmunohistochemistry.RESULTS:Fibroblast cytotoxicity and mouse lethality ofH-LPS were weaker than those of E-LPS.But the ability ofcoagulating limulus lysate of the two LPSs was similar(+/0.5 ng/mL).At 0.5 h after H-LPS injection,the bloodpressures of the 3 rabbits rapidly declined.At 1.0 h afterH-LPS injection,the blood pressures in 2 of the 3 rabbits fellto zero causing death of the 2 animals.For the other onerabbit in the same group,its blood pressure graduallyelevated.At 0.5 h after E-LPS injection,the blood pressuresof the three rabbits also quickly declined and thenmaintained at low level for approximately 1.0 h.At 0.5 hafter injection with H-LPS or E-LPS,PBMC numbers ofthe rabbits showed a remarkable increase.The totalpositivity rate of H-LPS from 126 biopsy specimens was60.3%(76/126).H-LPS positivity rate in the biopsy specimensfrom chronic gastritis (50/68,73.5%) was significantly higherthan that from gastric ulcer (26/58,44.8%) (x~2=10.77,P<0.01).H-LPS positivity rates in biopsy specimens fromchronic superficial gastritis (38/48,79.2%) and chronicactive gastritis (9/10,90.0%) were significantly higher thanthat of the patients with atrophic gastritis (3/10,30.0%)(x~2=7.50-9.66,P<0.01).CONCLUSION:The biological activities of H-LPS were weaker than those of E-LPS,the activities of H-LPS oflowering rabbit blood pressure and inducing rabbit PBMCwere relatively stronger.H-LPS may play a critical role ininducing inflammatory reaction in human gastritis. AIM: To determine the biological activity of Helicobacter pylori (H pylori) lipopolysaccharide (H-LPS) and understandpathological correlation between H-LPS and human chronic gastritis and peptic ulcer. METHODS: H-LPS of a clinical Hpyloristrain and LPS of Escherichia coli strain O55: B5 (E-LPS) were extracted by phenol-water method. Biological activities of H-LPS and E-LPS were detected by limulus lysate assay, pyrogen assay, blood pressure test and PBMC induction test in rabbits, cytotoxicity test in NIH 3T3 fibroblast cells and lethalitytest in NIH mice. Using self-prepared rabbit anti-H-LPSserum as the first antibody and commercial HRP-labeledsheep anti-rabbit sera as the second antibody, H-LPS inbiopsy specimens from 126 patients with chronic gastritis (68 cases) or gastric ulcer (58 cases) were examined by immunohistochemistry .RESULTS: Fibroblast cytotoxicity and mouse lethality of H-LPS were weaker than those of E-LPS.But the ability ofcoagulating limulus lysate of the two LPSs was similar (+ / 0.5 ng / mL) .At 0.5 h after H-LPS injection, the bloodpressures of the 3 rabbits rapidly declined. At 1.0 h after H-LPS injection, the blood pressures in 2 of the 3 rabbits fell to zero causing death of the 2 animals.For the other onerabbit in the same group, its blood pressure graduallyelevated. At 0.5 h after E-LPS injection, the blood pressures of the three rabbits also rapidly declined and thenmaintained at low level for approximately 1.0 h.At 0.5 hafter injection with H-LPS or E-LPS, PBMC numbers of the rabbits showed a remarkable increase in the total positive rate of H-LPS from 126 biopsy specimens was 60.3% (76/126) .H-LPS positivity rate in the biopsy specimens from chronic gastritis (50/68, 73.5%) was significantly higherthan that from gastric ulcer (26 / 58,44.8%) (x ~ 2 = 10.77, P <0.01) .H-LPS positivity rates in biopsy specimens from chronic superficial gastritis chronicactive gastritis (9/10, 90.0%) were significantly higher thanthat of the patients with atrophic gastritis (3/10, 30.0%)(X ~ 2 = 7.50-9.66, P <0.01). CONCLUSION: The biological activities of H-LPS were weaker than those of E-LPS, the activities of H-LPS of lowering rabbit blood pressure and inducing rabbit PBMCwere relatively stronger. H -LPS may play a critical role ininducing inflammatory reaction in human gastritis.