Fig 2: L-lactate mediates destabilization of C4b binding to H. pylori.a Schematic diagram of C4 primary activation and secondary degradation, adapted from35. b Western blot of C4 protein and products after activation in the presence of WT and ?lctP H. pylori over 60 min, using non-reducing gels. A positive control of complement activation and C4c formation was triggered by heated human IgG. Positions of C4, C4b, and C4c are shown at the left, and molecular weight is indicated on the right. The result is representative of three independent experiments with triplicate biological samples. c H. pylori PMSS1 WT was grown ± L-lactate and then treated by 10% NHS for the indicated time periods. Each sample was split into three: (1) treated by sample buffer only (total C4b); (2) centrifuged at 3000 × g for 3 min before adding sample buffer (bound C4b); (3) treated by sample buffer plus the reducing agent beta-mercaptoethanol (BME) (C4 ß-chain). All protein samples were run on 5-7% SDS PAGE and blotted with anti-C4 antibody. d Quantification of the experiment shown in (c), from three independent experiments. Bands were quantified by normalizing each band to the amount of total C4b or bound C4b at 3 min (leftmost band in each treatment group) using the Bio-Rad Image Lab software. Each point represents a biological sample for an independent experiment. The data were combined from the three independent experiments (represented as mean ± SD). The p values were obtained from unpaired two-tailed t-tests. The significance is indicated as * (p < 0.05), *** (p < 0.001), **** (p < 0.0001), or n.s. (not significant). Source data and exact p-values are provided in the Source Data file.