Abstract: 　Objective To observe the dynamic changes in collagen type Ⅰ and collagen type Ⅲ in rabbits with schistosomiasis japonica and the treatment effect of gamma interferon on the degradation of collagens in schistosomal hepatic fibrosis.Methods Each rabbit was infected with 80±1 S japonicum cercariae. Liver operations were done at different time points after infection and the liver specimens were embedded with paraffin and stained with α SMA, HE and picric acid Sirius red. The stained slides were observed under polarizing microscope and different collagen areas calculated by computer imagine analysis system. At the 16th week after infection, the infected rabbits received a single dose of praziquantel and gamma interferon for 8 weeks.Results The area percent of collagen type Ⅰ at the 28th week after infection (40 14±17 00) increased about seven fold compared with the 8th week group (5 73±3 40). The area percent of collagen type Ⅲ at the 28th week after infection (6 80±5 19) increased about six fold compared with the 8th week group (1 15±1 34). The α SMA positive cells also increased significantly. After gamma interferon treatment, the area percent of collagen type Ⅰ and type Ⅲ decreased significantly, from 18 51±7 52 and 4 63±3 64 (before treatment) to 3 09±1 54 and 0 40±0 37 (0 and 4 weeks after treatment) ( P <0 01). However, after the withdrawal of gamma interferon treatment,the collagen degradation was reversible.Conclusion Gamma interferon is effective in the treatment of hepatic fibrosis in rabbits infected with S japonicum ,the effect being reversible.

Key words: Schistosoma japonicum, hepatic fibrosis, gamma interferon (IFN-γ), collagen type Ⅰ, collagen type Ⅲ