Histopathological studies on chronic mouse hepatitis by natural Helicobacter infection

It has been known that Helicobacter hepaticus or Helicobacter bilis infection in mice cause chronic inflammation of the colon and liver. Chronic active hepatitis in mice occurred during carcinogenic study at NIRS in 2005. SPF C3H/HeNrs mice were used for 56~63 week-carcinogenic study by single gamma-ray irradiation. Liver, kidney, Harderian gland, bone marrow and thymus were collected and assessed histological and immunohistochemical examinations. 103 cases among 978 male mice had hepatic lesions. Chronic hepatitis occurred frequently in mice exposed high-dose irradiation compared to non-irradiated mice in one lot. 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 with an antibody against Helicobacter pyroli. It was suggested that these chronic hepatitis caused by Helicobacter spp. It was also presumed that immunosuppression by irradiation might influence on incidence of chronic hepatitis. Therefore, control of the infection is important for long-term animal study.第１４９回日本獣医学