OBJECTIVE: In vitro to investigate the regulation effects of Lactobacillus acidophilus ATCC4356 and L. bulgaricus (LB) on the activation of NF-kB and IL-8 secretion of SGC7901 cell, which Helicobacter pylori induced. METHODS: SGC7901 cell was cultured to reach the exponential growth phase, then adjusted to cell concentration (2.5 x 10(5)/mL), and planted into six shadow mask and incubated for 24 hours. Until reaching exponential growth phase, the cultured ATCC4356 and LB were adjusted to different concentration to incubation with SGC7901 cell together for one hour, and then added H. pylori into them for culturing 3 hours. For the contrast analysis of result, the experiment subgroups were designed as follow: normal control, H. pylori stimulating group (H. pylori group), ATCC4356 intervention group (ATCC4356 group) and LB intervention group (LB group). The nuclear factor-kB of SGC7901 cell was detected by immunohistochemistry. The release of IL-8 in cells was detected by ELISA. RESULTS: The percentage of NF-kB p65 positive nuclei-stained cell and the secreting level of IL-8 from cells in H. pylori group significantly increased compared with those in control group (P < 0.01). When the Lactobacillus concentration was 3 x 10(6) cfu/mL, 3 x 10(7) cfu/mL and 3 x 10(8) cfu/mL respectively, the percentage of NF-kB p65 positive nuclei-stained cell of ATCC4356 group was significantly decreased compared with that of H. pylori group (P < 0.01). When the Lactobacillus concentration was 3 x 10(6) cfu/ mL and 3 x 10(7) cfu/mL respectively, the IL-8 secretory volume of cells of ATCC4356 group could be significantly decreased compared with that of H. pylori group (P < 0.01). When the Lactobacillus concentration was 3 x 10(6) cfu/ mL, 3 x 10(7) cfu/mL and 3 x 10(8) cfu/mL respectively, the percentage of NF-kB p65 positive nuclei-stained cell of LB group was significantly decreased compared with that of H. pylori group (P < 0.05). When the Lactobacillus concentration was 3 x 10(7) cfu/mL or 3 x 10(8) cfu/mL respectively, the cell IL-8 secretory volume of LB group was significantly decreased compared with that of H. pylori group (P < 0.05). However, if the level of Lactobacillus concentration showed too high, the ATCC4356 and LB might have no above mentioned inhibitory action, the percentage of NF-kB p65 positive nuclei-stained cell and the level of IL-8 secretion of cells in those experiment groups significantly increased compared with those in H. pylori group. CONCLUSION: In some concentration range, both ATCC4356 and LB can inhibit the cell inflammatory reaction induced by H. pylori, but if the concentration is too high, they may make the inflammatory reaction become more serious. These can explain in partial why lactobacillus as primary common bacterium maintains the proper proportion concentration is very important for the keeping on microecological balance in stomach.