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Figure 5: Interleukin-8 production by 16-HBE cells, corrected for cell proliferation and expressed as a % of exposure with the corresponding pH without pepsin (control). Interleukin-8 release induced by pepsin is higher at pH 1.5 compared to pH 2.5 (mean difference 221%; ). Data expressed as mean (histograms) and SEM (bars) for 3 replicates. See supplement Figure  3 for induction of IL-8 at all pepsin concentrations and pH levels used in the statistical analysis.