Interleukin-12 Drives the Th1 Signaling Pathway in Helicobacter pylori -Infected Human Gastric Mucosa

Abstract

ABSTRACT In this study we examined mechanisms that regulate T-helper lymphocyte 1 (Th1) commitment in Helicobacter pylori -infected human gastric mucosa. The levels of gamma interferon (IFN-γ), interleukin-4 (IL-4), and IL-12 in total extracts of gastric biopsies taken from H. pylori -infected and uninfected patients were determined by an enzyme-linked immunosorbent assay. The levels of signal transducer and activator of transcription 4 (STAT4), STAT6, and T-box expressed in T cells (T-bet) in total proteins extracted from gastric biopsies were determined by Western blotting. Finally, the effect of a neutralizing IL-12 antibody on expression of Th1 transcription factors and the levels of IFN-γ in organ cultures of H. pylori -infected biopsies was examined. Increased levels of IFN-γ and IL-12 were found in gastric biopsy samples of H. pylori -infected patients compared to the levels in uninfected patients. In addition, H. pylori -infected biopsies exhibited high levels of expression of phosphorylated STAT4 and T-bet. Higher levels of IFN-γ and expression of Th1 transcription factors were associated with greater infiltration of mononuclear cells in the gastric mucosa. By contrast, production of IL-4 and expression of phosphorylated STAT6 were not associated with the intensity of mononuclear cell infiltration. In ex vivo organ cultures of H. pylori -infected biopsies, neutralization of endogenous IL-12 down-regulated the expression of phosphorylated STAT4 and T-bet and reduced IFN-γ production. Our data indicated that IL-12 contributes to the Th1 cell commitment in H. pylori -infected human gastric mucosa.