Galectin-1Ameliorates Rejection Of Liver Allografts From Flt3L-pretreated Donors In Mice

Part I:Mechanisms of spontaneous tolerance to mouse liver allograftObjectivesLiver allografts in mice are spontaneously accepted across major histocompatibility complex (MHC) incompatible barriers without requirement of immunosuppressive therapy. The mechanisms underlying spontaneous liver transplant tolerance and the tolerogenicity of liver allografts remain poorly understood. The aim of our study is to investigated the role of Thl, Th17, CD4+CD25+Foxp3+regulatory T cells, donor-derived dendritic cells and apoptosis alloreactive T cells in spontaneous tolerance of liver allografts in mice.MethodsMouse orthotopic liver transplantation was performed. H&E histological analysis and immunohistochemistry was used to assess cell infiltration of liver grafts. Real-time PCR and intracellular staining by flow cytometry was performed to detect the levels of Th1, Th17, CD4+CD25+Foxp3+regulatory T cells and their associated cytokines in the liver grafts. TUNEL assay was performed to detect the apoptosis of graft-infiltrating cells and splenocytes. To explore the role of donor-derived dendritic cells, Flt3L was administered to the donor mice before liver transplantation.ResultsMHC-mismatched B6liver allografts were spontaneously accepted by C3H recipients without a requirement for any immunosuppressive therapy. Increased frequencies of Thl, Th17and CD4+CD25+Foxp3+regulatory T cells were detected within liver allografts after liver transplantation. High levels of T lymphocyte apoptosis were dectected in liver allograft-infiltrating cells and T cell areas of recipient spleens. Pretreatment of donors with Flt3L resulted in acute rejection of liver allografts.ConclusionsClonal deletion of alloreactive T cells but not "clonal ignorance" contributes to spontaneous acceptance of MHC-disparate liver allografts in mice. Th1and Th17cells are the mediators of liver allograft rejection in the early phase after liver transplantation. CD4+CD25+Foxp3+regulatory T cells contribute to the induction and maintenance of liver transplant tolerance. Apoptosis as a main mechamism of clonal deletion of alloreactive T cells plays a crucial role in spontaneous tolerance of liver allografts in mice. The function of donor-derived dendritic is a key factor in determining the outcome of liver allografs after liver transplantion. Part â…¡:Galectin-1prolongs survival of liver allografts from Flt3L-pretreated donors in miceObjectivesRecent studies support the idea that galectin-1is able to induce apoptosis of activated T cells, selectively blunt Thl and Th17responses, inhibit secretion of pro-inflammatory cytokines and promote the generation of tolerogenic dendritic cells. The present study was designed to investigate the role of galectin-1in spontaneous tolerance of liver allograft, and the effect of galectin-1on Flt3L-triggered acute liver allograft rejection in mice.MethodsMouse orthotopic liver transplantation was performed. The effect of galectin-1blockade by anti-galectin-1mAb on liver allograft survival was determined. The effect of recombinant galectin-1administration on survival of liver allografts from Flt3L-pretreated donors was evaluated. We further investigated the influence of recombinant galectin-1on DC-triggered proliferation of allo-CD4+T cells in vitro.ResultsGalectin-1production is increased after liver transplantation; Blockade of galectin-1alone fails to disrupt the development of liver transplant spontaneous tolerance; Administration of rGal-1prolongs the survival of liver allografts from Flt3L-pretreated donors; Administration of rGal-1increases apoptosis of T cells in both liver allografts and recipient lymphoid tissue; Administration of rGal-1suppresses Flt3L-triggerd alloimmune response; Galectin-1inhibits FL-DC-mediated allo-stimulation of CD4+T cells in vitroConclusionsGalectin-1ameliorates rejection of liver allografts from Flt3L-pretreated donors in mice by inducing apoptosis of alloreactive T cells, inhibiting Th1and Th17responses, and promoting IL-10production.