Effects of γ-interferon on hepatic fibrosis of schistosoma japonicum-infected mice

AIM: To probe the effect of γ-IFN on hepatic fibrosis in schistosomiasis japonica.

METHODS: The amount and distribution of γ-IFN and extracellular matrix in the liver of 60 S. japonicum infected mice and 30 healthy mice at different stages, and their dynamics in 20 infected mice after administration of recombinant γ-interferon were determined by immunohistochemical streptavidin biotin peroxidase complex method.

RESULTS: The amount of γ-IFN in liver peaked at the 16^th week after infection (3 mice respectively reached 2+, 3+ and 4+ grade), which was higher than the levels of infected mice at the 8^th-12^th week (P < 0.01), and γ-IFN was mostly distributed around egg granuloma. Fibronectin, laminin, type I and III collagens in liver of most infected mice reached 1+ grade and individual 2+ grade at the 8^th week after infection, which were higher than those of healthy controls (P < 0.01), and were linearly distributed around egg granuloma . With chronicity and decrease of γ-interferon, however, the matrix proteins and collagens gradually increased, peaked respectively at the 20^th and 24^th week (over 70% infected mice with 3+ to 4+ grade), became wide and thick, and deposited in band like or retiform shape around and in egg granuloma. After administration of γ-IFN, only 3 infected mice had 2+ grade of fibronectin at the 20^th week, and 2 mice had 3+ grade of type III collagen at the 24^th week, and none of them reached 4+ grade, which were significantly less than the untreated group at the same stage (P < 0.01-0.05).

CONCLUSION: γ-interferon may play an important role in opposing the inflammatory response of egg granuloma, decreasing secretion and deposition of extracellular matrix in the liver and suppressing hepatic fibrosis.