The appearance of unusual phenotypic cells (CD4+ Mac-1+ class II+) in the liver of (NZW x BXSB)F1 mice is possibly an animal model for autoimmune hepatitis.

The male (NZW x BXSB)F1 (W/BF1) mouse, a murine model for autoimmune diseases, shows hepatosplenomegaly with lymphoid cell infiltration in the liver by 20 weeks of age. The majority of infiltrating cells are T cells, B cells and plasma cells, as seen in autoimmune hepatitis. Together with the increase in serum glutamate pyruvate transaminase (GPT) levels, anti-dsDNA antibody (Ab) and circulating immune complex (CIC) levels increase with age. These findings are compatible with those of autoimmune hepatitis in humans. In addition, a unique finding in this mouse is the accumulation of CD4+ Mac-1+ Class II+ cells in the sinusoidal space. The cells have the capacity to proliferate and differentiate into macrophages in vitro, indicating that they are the precursors of macrophages. This W/BF1 mouse provides a useful tool for not only analyzing the pathogenesis of autoimmune hepatitis but also establishing a new therapeutic strategy for it. In addition, we discuss the significance of the appearance of abnormal cells in autoimmune-prone mice.