Role Of Kupffer Cells In The Immunoregulation Of Orthotopic Liver Transplantation In Rats

Objective This study was conducted (1) to establish experimental model of ortho topic liver transplantation (OLT) with acute rejection and without rejection, observe the expression of FasL protein in kupffer cells and the changes of cytokine levels in plasma . (2) to observe the apoptosis of T lymphocytes and the expression of Caspase-3 in liver allografts . (3) to examine the function of kupffer cells isolated from the grafts and the cytotoxicity of kupffer cells against lymphocytes .Methods (1) Ortho topic liver transplantation was performed by the two-cuff method .Rats were randomly divided into two groups : group A, the acute rejection group ; group B, the immune tolerance group . The normal livers were served as control group (group C). Rats samples were collected on 3, 5, 7 days after operation. (2) Recipient survival rate, histopathological characteristics were detected . Plasma levels of TBIL, AST, ALT and ALB were measured with an automatic biochemical analyzer . Cytokine levels (TNF- α, IL-10 and TGF- β₁) in plasma were also measured with enzyme linked immunosorbent assay. Expression of FasL protein in kupffer cells and caspase-3 in lymphocyte were evaluated with immunohistochemical staining .The apoptosis of lymphocyte was detected by TUNEL. (3) kupffer cells in normal liver and liver grafts were isolated 7days after operation. Theexpression of FasL protein in kupffer cells was measured by flow cytometry(FCM) and the effect of kupffer cells on lymphocytes was also evaluated.Results (1) Duration of operation was not significantly differentbetween A and B group . Without using any immunosuppressive therapy, A group showed typical acute rejection with severely impaired liver function , The rats died 8 to 14 days after transplantation, the average survival time is 9.4 days. The rats of B group showed no acute rejection after transplantation ,mild morphologic and liver function changes were observed . The rats could survive for more than 14 days if no complication occurred. (2) Plasma level of TNF-a increased significantly in A group and IL-10 and TGF- P i mainly increased in B group . (3) Expression of FasL in kupffer cells of B group was significantly higher than that in A group ,companied by higher apoptotic rate of lymphocytes and higher expression of Caspase-3 in lymphocytes. There was significant different between the two groups. (4)After isolation of kupffer cells, higher expression of FasL was detected by FCM in B group compared with A and C group. The kupffer cells isolated from B group induced more apoptotic lymphocytes than kupffer cells from A and C group when cultured with lymphocytes.Conclusions (1) The donor liver of Wistar rats and recipient SD rats combination is a high rejection model and the combination of Wistar to Wistar shows no rejection, but immune tolerance. (2) kupffer cells can express functional FasL protein after liver transplantation , kupffer cells-mediated T lymphocytes apoptosis via the Fas/ FasL pathway may play animportant role in liver transplantation tolerance.(3) Apoptosis of lymphocytes occurs via the Caspase pathway. (4) Kupffer cells may play an important role in the changes of plasma cytokines.