Kupffer Cells Promote Acute Rejection Via Induction Of Th17 Differentiation In Rat Liver Allograft

Objective:Orthotopic liver transplantation (OLT) is applied as a valuable method for treating end-stage liver diseases. However, acute rejection is one of its most serious complication reported in～about 30% of liver transplants performed. T lymphocytes and Kupffer cells are the dominant cell types that are found to infiltrate the liver following transplantation. Consistent with these observations, CD4+ T cells have been proposed to play a crucial role in determining transplant rejection or tolerance. T helper (Th) 17, recently identified as a new subset of CD4+ T cells, has been discovered to implicate in transplant rejection. Data from animal experiments and clinical trials confirmed that Thl 7 cells have a role in allograft rejection of solid organs, which previously thought to be driven by Th1-mediated inflammation. Kupffer cells are macrophage that are present in liver and localize to portal area and within sinusoidal lumen. Kupffer cells have previously been implicated in the pathogenesis of hepatic allograft rejection based on their antigen presentation and cytokine production. As antigen presenting cells (APC) are associated with liver, Kupffer cells interact with lymphocytes to induce T-cell proliferation and cytokine synthesis. Furthermore, under pathophysiological conditions, Kupffer cells have been shown to secrete high levels of IL-6 and TGF-β, which are key factors for Th17 cell differentiation. Therefore, we wonder if it is possible that Kupffer cells induce Th17 cell differentiation via production of IL-6 and TGF-βto promote acute liver allograft rejection. To test this hypothesis, the role of Kupffer cells and Th17 cells in acute liver transplant rejection was investigated using a rat OLT model.Methods:A rat model of allogeneic liver transplantation from Dark Agouti (DA) to Brown Norway (BN) was established with or without pretreatment with gadoliniumchloride (GdCl3), and isogeneic liver transplantation (BN to BN) was used as a control. The expression of kupffer cells cell-derived Th17-related cytokines in liver and peripheral blood were determined by immunohistochemistry, flow cytometry or ELISA, and survival differences were compared between groups. Furthermore, Kupffer cells in liver grafts were isolated and cocultured with naive CD4+ T cells for 5 days, then T cells were collected and the frequency of Th17 differentiation was determined using flow cytometry.Results:Both Kupffer cells and Th17 cells were found to infiltrate into liver allografts accompanied by increase of IL-6 and TGF-βlevels. Pretreatment with GdCl3 attenuated intragraft-infiltration of Th17 cells as well as Kupffer cells, decreased IL-6 and TGF-βlevels in grafts, improved liver function and prolonged the survival time(16.33±0.96 days vs 11.50±0.99 days, p<0.01). In vitro, the Kupffer cells from allograft liver secreted significantly more IL-6, TGF-βand induced Th17 differentiation more effectively comparing with those from isograft (30.8% vs 8.1%).Conclution:Kupffer cells potentially function as inducers of Th17 cells by secreting IL-6 and TGF-β, and promote acute liver allograft rejection.