Histopathological Studies on Cases of Chronic Mouse Hepatitis by Natural Helicobacter Infections

概要

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It has been known that Helicobacter hepaticus or Helicobacter bilis infection cause chronic inflammation of the colon and liver. Chronic active hepatitis was found in radiation exposure experiments using male C3H/HeNrs mice at our institute. Histopathologically, 103 cases among 978 mice (64–91 weeks of age at autopsy) had hepatic lesions regardless of irradiation exposure. Mild lesions showed only focal necrosis and focal inflammation in the liver. Severe cases were accompanied by hepatocytomegaly, bile duct hyperplasia, hypertrophy and activation of Kupffer cells, cholangitis, pleomorphic hepatocytes and/or tumor. Helical-shaped bacteria were detected between hepatocytes by Warthin-Starry silver stain and immunohistochemistry (IHC) with an antibody against Helicobacter pylori. It was suggested that these chronic hepatitis caused by Helicobacter spp. Although chronic hepatitis occurred frequently in mice exposed high-dose irradiation compared to non-irradiated mice in one lot, it was not concluded whether radiation might influence in incidence or degree of hepatitis or not. Our report suggested that natural Helicobacter spp. infection in mice can occur in an experimental animal facility. Therefore, it is suggested that monitor of the Helicobacter infection is very important for quality control of animal experiments.