[Pathogenesis of aleutian mink disease. VII. Chronic hepatitis with bile duct proliferation].

Aleutian disease is a chronic persistent viral infection of mink characterized by hypergammaglobulinema, generalized plasmacytosis, sclerosing glomerulonephritis, polyarteritis, and plasma cell hepatitis with bile duct proliferation. The development of hepatic lesions was studied both light- and electron-microscopically in mink experimentally infected with Aleutian disease virus. Fifteen normal and 99 mink experimentally infected with Aleutian disease virus were used. Experimental mink were killed in intervals from 3 weeks to 23 months after infection, and liver sections were processed for both light- and electron-microscopic studies. Experimentally infected mink developed portal and intralobular lymphocytic and plasmacytic infiltrates in the liver 3 weeks after infection. Four to five weeks after infection there was evidence of early bile duct proliferation that began as an outgrowth of the portal bile ducts. Three to five months after infection a marked bile duct proliferation was present in some of the portal triads and adjacent liver lobules; but there was no tendency of these lesions to progress into biliary cirrhosis. Ultrastructural characteristics of proliferating bile duct cells were marked deformation, formation of multiple cell layers, reduction in the number of microvilli and desmosomes, and infiltration of the epithelial cells by lymphoid cells and plasmacytes. The hepatic lesions either develop by direct virus stimulation or by the deposition of virus-antibody complexes.