| Background and objective: Biliary atresia(BA) is a pediatric liver disease characterized by progressive inflammation and fibrosis of both the extrahepatic and intrahepatic bile ducts. A current view of the pathogenesis of BA is that autoimmune response triggered by viral infection may play a predominant role in the progression of bile duct injury. Nevertheless, the mechanism is not fully understood. Our team reported for the first time that IL-17+T cells infiltrating into the portal areas play a role in immune damage of bile ducts. Recent literatures demonstrate activation of γδT cells secrete Il-17 A functioning in autoimmune diseases.Therefore we speculate that γδT cells possibly play an important role in immunological damage of bile ducts in BA. In this research we aim at the following vital issues.Methods: Used RRV to establish mice model of biliary atresia, newborn Balb / c mice were randomly divided into two groups: BA group and Control group. RRV or 0.9% saline was injected intraperitoneally within the first 12 h of birth, respectively. The concentrations of cytokines in the liver, including IL-17 A, IL-6, IL-23, were measured with ELISA kits according to the manufacturer’s protocols. The infiltration of Th17 in liver was measured by fluorescent immunohistochemistry. The proportion of Th17 cells in CD4+ cells in livers were detected by flow cytometry(FCM) in each group. Treatment of mice: digoxin and anti-IL-17 Ab was injected i.p. daily for 6 days, starting from 24 h post-RRV injection, while injected the same volume of 0.9% saline to Control group. The stool color, weight gain and jaundice in the BA phenotype mice were monitored. Immunohistochemistry was used to detect the location and changes of γδT cells in livers of infants suffering BA and the proportion of γδT cells in livers were detected by flow cytometry.Results:1) There is a significantly higher level of IL-6 was found in the livers of BA mice compared with controls. Expression of IL-6 was rising from 4d post-RRV injection and reaching an apex at day 7, which is 30-fold higher than Control group(p<0.001). Expression of IL-17 A and IL-23 were rising from day 4 and reaching an apex at day 11 post-RRV injection, and 5.5-fold of IL-17 A, 4.5-fold of IL-23, respectively, compared with Control group(p<0.01, p<0.001). It showed that CD4+IL-17A+ T cells infiltrated into portal areas by immunofluorescence staining in BA mice at day 7 post-RRV injection. According the FCM, the percentage of CD4+IL-17+ T cells was rising at day 4 and significantly increased, reaching an apex, at day 7 and then decreased in RRV-induced BA mice compared with saline-injected control mice. 2) After digoxin and anti-IL-17 Ab was injected, the two group both has a lower incidence of BA, decreased cellular infiltration in the liver and attenuated BA symptoms with improved survival. Moreover, the treatment with anti-IL-17 Ab group seems more effective than digoxin group: lower incidence of BA(anti-IL-17Ab:digoxin =66.7%:75.0%, p<0.01, P<0.001, compared with RRV), decreased cellular infiltration(p<0.01) and longer survival(anti-IL-17Ab:digoxin =78.2%:59.6%, p< 0.01, p < 0.001, compared with RRV). 3) γδT cells are scattered in the interface areas of inflamed portal tracts of BA livers in infants. BA tissues contained more γδT cells. The percentage of γδT cells in the liver of BA patients was significantly elevated compared with the healthy controls(p<0.05).Conclusion: The up-regulation of liver γδT cells in BA might contributes to the occurrence and the bile duct injury of the disease, through secreting IL-17 A accompany with Th17 cells. |
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