Background: Blocking the 4-1BB/4-1BB ligand (4-1BBL) signal may modulate the secretion of Th1/Th2 cytokines and prolong the survival of the grafts, which play a key role in organ transplantation tolerance. The aim of this study was to investigate the role of blockade of the 4-1BB/4-1BBL co-stimulatory pathway with 4-1BBL monoclonal antibody (mAB) in acute rejection of rat orthotopic liver transplantation.
Methods: The orthotopic liver transplantation model was set up, while male Lewis rats were used as liver donors and Brown-Norway rats as recipients. The recipient rats were intravenously injected with anti 4-1BBL mAB or isotype control antibody. Groups were monitored for graft survival after transplantation. Plasma chemistry, including aspartate transaminase (AST), alanine aminotransferase (ALT), and bilirubin (BIL), was assayed. The concentrations of interleukin (IL)-2, IL-10 and interferon (IFN)-gamma in plasma were also measured by enzyme-linked immunosorbent assay. Allograft histology images were collected under light microscope and electron microscope.
Results: Isotype antibody treated recipients exhibited elevated plasma levels of liver injury markers including AST, ALT and BIL, progressive portal and venous inflammation and cellular infiltration of the liver allografts, and a mean graft survival time (MST) of 10.9 days. Administration of anti 4-1BBL mAB resulted in a decrease in plasma levels of liver injury markers and the concentrations of IL-2, IL-10 and IFN-gamma. The histological grade of rejection on day 7 decreased and MST (17.3 days) increased substantially.
Conclusions: These results demonstrate that attenuation of acute rejection follows the blockade of the 4-1BB/4-1BBL co-stimulatory pathway with 4-1BBL monoclonal antibody and strongly suggest it is a promising strategy to prevent progression of graft rejection by suppressing T cell-mediated immunity.