Objective To clarify the relationship between tumor necrosing factor(TNF) receptor-associated factor 2(TRAF2)gene deletion and liver failure and to explore the probable mechanism.Methods TRAF2 gene deficient mice(TRAF2~(lox/lox)/Cre~+,TRAF2~(lox/lox)/Cre~+/TNF~(-/-)) and control mice(TRAF2~(lox/lox)/Cre~-,TRAF2~(lox/lox)/Cre~-/TNF~(-/-))were simultaneously injected with PolyI:PolyC(300?L per injection one for 3 days,3 injections in succession)to induce TRAF2 gene knockout.The gene deletion was verified by polymerase chain reaction(PCR).The dynamic change of sera alanine aminotransferase(ALT)in animal model was investigated.These mice were sacrificed for liver when TRAF2~(lox/lox)/Cre~+ mice were severe sick and dying.Several pieces of liver tissues were speedily frozen,embedded by OCT and sectioned.Then,hematoxylin and eosin staining was performed.The pathological manifestation was investigated by light microscope.Expression of Fas and CD40 on hepatoeytes isolated from these mice' livers was determined by flow analyzers and cell sorters(FACS).The purified hepatocytes incubated with TNF(100?g/L)were stained by thiazolyl blue(MTT)at 30 rain,1 h,4 h和20 h respectively,then optics density values were determined.The proportion of viable hepatocytes was counted.Results TRAF2~(lox/lox)/Cre~+ mice were sick 5 to 9 days after injection with Poly(?):PolyC; and TRAF2 genes were successfully deleted.ALT started to increase at 2 days after injection,peaking at day 4(234.80?12.34)U/L and beginning to decrease before death.In TRAF2~(lox/lox)/Cre~+/TNF~(-/-) mice whose TRAF2 genes were also successfully deleted, although ALT levers also increased(90.30?15.63)U/L,the mice did not show any illness symptom up to day 15.Pathological results showed that there were obvious liver cells necrosis and inflamma- tion cells infiltration in TRAF2~(lox/lox)/Cre~+ mice livers.Moreover,Fas expression increased in TRAF2~(lox/lox)/Cre~+/TNF~(-/-)mice compared with that in control,hut CD40 decreased.Conclusions These results suggest that TRAF2 gene deletion can lead to hepatocytes death,and induce fulminant liver failure in mice.It is probably the reason why depletion of TRAF2 in hepatocytes sensitizes hepatocytes to TNF-mediated death

F0.01(1,5)=16. 30,P0. 05). Conclusion Laboratory results thus suggest that infection intensity is related to snail size per se, whereas prevalence in the field is related to snail size only through the correlation between size and age. In addition, under these experimental conditions, infected snails were no larger than uninfected snails, so the gigantism snails observed in the field might not be attributable to Trichobilharzia-induced effect.