Two-dimensional difference gel electrophoresis, combined with immunoblotting, confirmed that the levels of gene products, including ATP synthase subunit alpha (ATP5F1A), pepsinogen A3 (PGA3), succinate dehydrogenase complex iron sulfur subunit B (SDHB), and progastricsin (PGC), were found to be decreased in patients with autoimmune gastritis [34]. This evidence concerns the gene PGA3 and autoimmune gastritis.