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The Role of Diverse Liver Cells in Liver Transplantation Tolerance.

ABSTRACT: Liver transplantation is the ideal treatment approach for a variety of end-stage liver diseases. However, life-long, systemic immunosuppressive treatment after transplantation is required to prevent rejection and graft loss, which is associated with severe side effects, although liver allograft is considered more tolerogenic. Therefore, understanding the mechanism underlying the unique immunologically privileged liver organ is valuable for transplantation management and autoimmune disease treatment. The unique hepatic acinus anatomy and a complex cellular network constitute the immunosuppressive hepatic microenvironment, which are responsible for the tolerogenic properties of the liver. The hepatic microenvironment contains a variety of hepatic-resident immobile non-professional antigen-presenting cells, including hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, and hepatic stellate cells, that are insufficient to optimally prime T cells locally and lead to the removal of alloreactive T cells due to the low expression of major histocompatibility complex (MHC) molecules, costimulatory molecules and proinflammatory cytokines but a rather high expression of coinhibitory molecules and anti-inflammatory cytokines. Hepatic dendritic cells (DCs) are generally immature and less immunogenic than splenic DCs and are also ineffective in priming naïve allogeneic T cells via the direct recognition pathway in recipient secondary lymphoid organs. Although natural killer cells and natural killer T cells are reportedly associated with liver tolerance, their roles in liver transplantation are multifaceted and need to be further clarified. Under these circumstances, T cells are prone to clonal deletion, clonal anergy and exhaustion, eventually leading to tolerance. Other proposed liver tolerance mechanisms, such as soluble donor MHC class I molecules, passenger leukocytes theory and a high-load antigen effect, have also been addressed. We herein comprehensively review the current evidence implicating the tolerogenic properties of diverse liver cells in liver transplantation tolerance.

SUBMITTER: Jiang Y

PROVIDER: S-EPMC7304488 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The Role of Diverse Liver Cells in Liver Transplantation Tolerance.

Jiang Yanzhi Y Que Weitao W Zhu Ping P Li Xiao-Kang XK

Frontiers in immunology 20200612

Liver transplantation is the ideal treatment approach for a variety of end-stage liver diseases. However, life-long, systemic immunosuppressive treatment after transplantation is required to prevent rejection and graft loss, which is associated with severe side effects, although liver allograft is considered more tolerogenic. Therefore, understanding the mechanism underlying the unique immunologically privileged liver organ is valuable for transplantation management and autoimmune disease treatm ...[more]

PMID: 32595648

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Project description:Immune responses induced by ongoing and/or past infections prevent the establishment of transplantation tolerance in experimental animal models. How host-pathogen interactions influence allograft tolerance in humans has not been investigated before. The spontaneous development of operational tolerance in liver transplant recipients with chronic hepatitis C virus (HCV) infection constitutes a unique setting to address this question. We conducted a clinical trial of immunosuppression withdrawal in stable HCV-infected liver recipients to elucidate: i) the mechanisms through which allograft tolerance is established in the presence of an ongoing inflammatory response; and ii) how is influenced by anti-HCV heterologous immune responses. Enrolled patients gradually discontinued their immunosuppressive drugs over 6-9 months, and those who maintained normal allograft status 12 months after drug withdrawal were considered operationally tolerant. Successful drug withdrawal was associated with intra-hepatic over-expression of type I interferon and immune-regulatory genes, and correlated with an expansion of exhausted PD1/CTLA4/2B4-positive HCV-specific circulating CD8+ T cells. These findings were already present before immunosuppression was discontinued and were specific for HCV infection. In contrast, the magnitude of HCV-induced inflammatory gene expression and the scope of anti-HCV effector T cell responses did not influence drug withdrawal outcome. Our data indicate that in humans persistent viral infections do not necessarily preclude the development of transplantation tolerance. At least in HCV-infected liver allografts, mechanisms associated with the capacity of the virus to evade adaptive immunity could contribute to the restraining of alloimmune responses and the establishment of transplantation tolerance. Transcriptomic study from the following liver tissue samples: 12 tolerant before immunosuppression (IS), 13 non-tolerant before IS, 4 from non-tolerant at the time of rejection, 13 from tolerant patients 12 months after IS discontinuation. Additionally, 8 liver tissue samples obtained from healthy living liver donors undergoing partial hepatectomy were included as non-transplanted controls.

Project description:During the last 5 decades, liver transplantation has witnessed rapid development in terms of both technical and pharmacologic advances. Since their discovery, calcineurin inhibitors (CNIs) have remained the standard of care for immunosuppression therapy in liver transplantation, improving both patient and graft survival. However, adverse events, particularly posttransplant nephrotoxicity, associated with long-term CNI use have necessitated the development of alternate treatment approaches. These include combination therapy with a CNI and the inosine monophosphate dehydrogenase inhibitor mycophenolic acid and use of mammalian target of rapamycin (mTOR) inhibitors. Everolimus, a 40-O-(2-hydroxyethyl) derivative of mTOR inhibitor sirolimus, has a distinct pharmacokinetic profile. Several studies have assessed the role of everolimus in liver transplant recipients in combination with CNI reduction or as a CNI withdrawal strategy. The efficacy of everolimus-based immunosuppressive therapy has been demonstrated in both de novo and maintenance liver transplant recipients. A pivotal study in 719 de novo liver transplant recipients formed the basis of the recent approval of everolimus in combination with steroids and reduced-dose tacrolimus in liver transplantation. In this study, everolimus introduced at 30 days posttransplantation in combination with reduced-dose tacrolimus (exposure reduced by 39%) showed comparable efficacy (composite efficacy failure rate of treated biopsy-proven acute rejection, graft loss, or death) and achieved superior renal function as early as month 1 and maintained it over 2 years versus standard exposure tacrolimus. This review provides an overview of the efficacy and safety of everolimus-based regimens in liver transplantation in the de novo and maintenance settings, as well as in special populations such as patients with hepatocellular carcinoma recurrence, hepatitis C virus-positive patients, and pediatric transplant recipients. We also provide an overview of ongoing studies and discuss potential expansion of the role for everolimus in these settings.

Dataset Information

The Role of Diverse Liver Cells in Liver Transplantation Tolerance.

Publications

The Role of Diverse Liver Cells in Liver Transplantation Tolerance.

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