Midzonal necrosis of the liver after concanavalin A-injection.

Concanavalin A (Con A) can induce an immune-mediated hepatitis. Since direct evidence of immune mechanism for this hepatitis is lacking, we employed adoptive transfer to study the mechanism of Con A-induced hepatitis. Intravenous administration of Con A (20 mg/kg) to Balb/c mice was accompanied by elevations of serum alanine aminotransferase (ALT) levels and midzonal necrosis with lymphocyte infiltration in the liver. None of the Balb/c nu/nu mice showed biochemical or pathologic hepatic abnormalities with the same dose of Con A. In the area of midzonal necrosis, CD4-positive T lymphocytes appeared at 24 hr after injection, and then both CD4-positive and CD8-positive T lymphocytes were found at the margin of zonal necrosis at 48 hr. Pretreatment with carrageenan, a potent inhibitor of macrophages, prevented these biochemical and pathologic changes. Mononuclear cells infiltrating in the liver of Balb/c mice 24 hr after priming with Con A were harvested and injected into Balb/c nu/nu mice injected with Con A 24 hr previously. Serum ALT levels elevated and the same pathologic changes observed in Con A-treated Balb/c mice were observed. These changes were not observed when the splenic cells from Con A-treated Balb/c mice were transferred to Con A-treated nude mice. These results suggest that Con A-induced hepatic injury is mediated by macrophages and T lymphocytes sensitized by Con A or its metabolites.