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1.
The role of the gut microbiome in graft fibrosis after pediatric liver transplantation.
Qin, T, Fu, J, Verkade, HJ
Human genetics. 2021;(5):709-724
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Abstract
Liver transplantation (LT) is a life-saving option for children with end-stage liver disease. However, about 50% of patients develop graft fibrosis in 1 year after LT, with normal liver function. Graft fibrosis may progress to cirrhosis, resulting in graft dysfunction and ultimately the need for re-transplantation. Previous studies have identified various risk factors for the post-LT fibrogenesis, however, to date, neither of the factors seems to fully explain the cause of graft fibrosis. Recently, evidence has accumulated on the important role of the gut microbiome in outcomes after solid organ transplantation. As an altered microbiome is present in pediatric patients with end-stage liver diseases, we hypothesize that the persisting alterations in microbial composition or function contribute to the development of graft fibrosis, for example by bacteria translocation due to increased intestinal permeability, imbalanced bile acids metabolism, and/or decreased production of short-chain fatty acids (SCFAs). Subsequently, an immune response can be activated in the graft, together with the stimulation of fibrogenesis. Here we review current knowledge about the potential mechanisms by which alterations in microbial composition or function may lead to graft fibrosis in pediatric LT and we provide prospective views on the efficacy of gut microbiome manipulation as a therapeutic target to alleviate the graft fibrosis and to improve long-term survival after LT.
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Liver-associated immune abnormalities.
Grunebaum, E, Avitzur, Y
Autoimmunity reviews. 2019;(1):15-20
Abstract
In recent years, the cross talk between the liver and the immune system is being uncovered, in part by studying liver involvement in primary immune deficiencies (PID) and in part by investigating the alterations of the immune system following orthotopic liver transplantation (OLT). Here we review some of the reciprocal interactions between the liver and the immune system. Patients with PID, particularly those involving inherited defects in T and B cells or innate immunity are prone to infections and inflammatory responses that often involve the liver. Omenn's syndrome, familial hemophagocytic lymphohistiocytosis, AIRE, FOXP3 and CD25 deficiencies, common variable immunodeficiency, CD40 ligand deficiency, chronic granulomatous disease and autoimmune lymphoproliferative syndrome are some of the notable PID associated with typical hepatobiliary abnormalities. Knowledge gained from studying these PID together with laboratory and histological evaluations can assist in managing PID-associated liver dysfunction. The liver itself also has important effects on the immune system, as evident from the growing experience with patients surviving OLT. Up to 40% of pediatric patients who receive OLT suffer from post transplantation allergy, autoimmunity, and immune-mediated disorders (PTAA). PTAA is more common after liver and heart transplantations than kidney transplantations. Potential contributing factors for the increased frequency of PTAA after OLT include the age of the patients, the prolonged use of tacrolimus and the reduced regulatory immune function with a shift towards a TH2 immune response. Better understanding of the mechanisms leading to the development of PTAA after OLT will also improve the management of these conditions.
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Dynamics of virus-specific T cell immunity in pediatric liver transplant recipients.
Arasaratnam, RJ, Tzannou, I, Gray, T, Aguayo-Hiraldo, PI, Kuvalekar, M, Naik, S, Gaikwad, A, Liu, H, Miloh, T, Vera, JF, et al
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons. 2018;(9):2238-2249
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Abstract
Immunosuppression following solid organ transplantation (SOT) has a deleterious effect on cellular immunity leading to frequent and prolonged viral infections. To better understand the relationship between posttransplant immunosuppression and circulating virus-specific T cells, we prospectively monitored the frequency and function of T cells directed to a range of latent (CMV, EBV, HHV6, BK) and lytic (AdV) viruses in 16 children undergoing liver transplantation for up to 1 year posttransplant. Following transplant, there was an immediate decline in circulating virus-specific T cells, which recovered posttransplant, coincident with the introduction and subsequent routine tapering of immunosuppression. Furthermore, 12 of 14 infections/reactivations that occurred posttransplant were successfully controlled with immunosuppression reduction (and/or antiviral use) and in all cases we detected a temporal increase in the circulating frequency of virus-specific T cells directed against the infecting virus, which was absent in 2 cases where infections remained uncontrolled by the end of follow-up. Our study illustrates the dynamic changes in virus-specific T cells that occur in children following liver transplantation, driven both by active viral replication and modulation of immunosuppression.
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4.
Longitudinal assessment of T cell inhibitory receptors in liver transplant recipients and their association with posttransplant infections.
Mysore, KR, Ghobrial, RM, Kannanganat, S, Minze, LJ, Graviss, EA, Nguyen, DT, Perez, KK, Li, XC
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons. 2018;(2):351-363
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Abstract
Current immunosuppression regimens in organ transplantation primarily inhibit T cells. However, T cells are also critical in protective immunity, especially in immune-compromised patients. In this study, we examined the association of T cell dysfunction, as marked by expression of T cell exhaustion molecules, and posttransplant infections in a cohort of liver transplant patients. We focused on Programmed Death 1 (PD-1) and T cell Ig- and mucin-domain molecule 3 (Tim-3), which are potent co-inhibitory receptors, and their persistent expression often leads to T cell dysfunction and compromised protective immunity. We found that patients with the highest expression of PD-1 +Tim-3+ T cells in the memory compartment before transplantation had increased incidence of infections after liver transplantation, especially within the first 90 days. Longitudinal analysis in the first year showed a strong association between variability of PD-1 and Tim-3 expression by T cells and infectious episodes in transplant patients. Furthermore, T cells that expressed PD-1 and Tim-3 had a significantly reduced capacity in producing interferon (IFN)-γ in vitro, and this reduced IFN-γ production could be partially reversed by blocking PD-1 and Tim-3. Interestingly, the percentage of Foxp3+ regulatory T cells in liver transplant patients was stable in the study period. We concluded that the functional status of T cells before and after liver transplantation, as shown by PD-1 and Tim-3 expression, may be valuable in prognosis and management of posttransplant infections.
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Microbiota and the liver.
Shen, TD, Pyrsopoulos, N, Rustgi, VK
Liver transplantation : official publication of the American Association for the Study of Liver Diseases and the International Liver Transplantation Society. 2018;(4):539-550
Abstract
The gut microbiome outnumbers the human genome by 150-fold and plays important roles in metabolism, immune system education, tolerance development, and prevention of pathogen colonization. Dysbiosis has been associated with nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), and alcoholic liver disease (ALD) as well as cirrhosis and complications. This article provides an overview of this relationship. Liver Transplantation 24 539-550 2018 AASLD.
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Mechanisms of liver-induced tolerance.
Moris, D, Lu, L, Qian, S
Current opinion in organ transplantation. 2017;(1):71-78
Abstract
PURPOSE OF REVIEW To highlight the results of the ongoing research on the mechanisms of liver-induced tolerance focusing on results from the last year. RECENT FINDINGS The liver is exposed to a massive antigenic burden of dietary and commensal products from the gastrointestinal tract via portal vein, most of which are necessary for survival. To prevent the immune system from destroying these foreign yet beneficial elements, the liver has developed unique mechanisms to suppress immune responses. It is thought that these mechanisms of acquired tolerance may also underlie the spontaneous acceptance of liver allografts observed after transplantation in many species. The fact that isolated hepatocyte transplants are acutely rejected, suggests that nonparenchymal liver cells play a critical role in spontaneous liver allograft acceptance. IFN-γ, a key inflammatory cytokine produced by T effector (Tef) cells, is paradoxically compulsory for spontaneous liver allograft acceptance. Analysis of IFN-γ signaling points to liver mesenchymal nonparenchymal liver cell that eliminate infiltrating Tef cells via expression of B7-H1, IL-10, and tumor growth factor-β, as well as the enhancement of Tregs and MDSCs. Thus, liver mesenchymal cells are thought to promote tolerance by eliminating alloreactive Tef cells and enhancing suppressor cells (T and B). SUMMARY The research during last year offered some key insights into the mechanisms of liver-induced tolerance. Through interactions with activated T cells and B cells via IFN-γ/B7-H1 pathways, liver mesenchymal cells have been shown to be critical components of liver-specific tolerance induction.
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Tolerance after liver transplantation: Where are we?
Feng, S, Bucuvalas, J
Liver transplantation : official publication of the American Association for the Study of Liver Diseases and the International Liver Transplantation Society. 2017;(12):1601-1614
Abstract
Impeccable management of immunosuppression is required to ensure the best longterm outcomes for liver transplant recipients. This is particularly challenging for children who arguably need 8 decades of graft and patient survival. Too little risks chronic, often subclinical allo-immune injury while too much risks insidious and cumulative toxicities. Historically, immunosuppression minimization or withdrawal has been a strategy to optimize the longevity of liver transplant recipients. The literature is sprinkled with single-center reports of operationally tolerant patients - those with apparently normal liver function and liver tests. However, without biopsy evidence of immunological quiescence, confidence in the phenotypic assignment of tolerance is shaky. More recently, multicenter trials of immunosuppression withdrawal for highly selected, stable, longterm adult and pediatric liver recipients have shown tolerance rates, based on both biochemical and histological assessment, of 40% and 60%, respectively. Extended biochemical and histologic follow-up of children over 8 years, equivalent to 7+ years off of drug, suggests that operational tolerance is robust. Therefore, clearly, immunosuppression can be completely and safety withdrawn from highly-selected subsets of adults and children. However, these trials have also confirmed that clinically ideal recipients - those eligible for immunosuppression withdrawal trial - can harbor significant and worrisome inflammation and/or fibrosis. Although the etiology and prognosis of these findings remain unknown, it is reasonable to surmise that they may reflect an anti-donor immune response that is insufficiently controlled. To achieve the outcomes that we are seeking and that our patients are demanding, we desperately need noninvasive but accurate biomarkers that identify whether immunosuppression is neither too much nor too little but "just right." Until these are available, liver histology remains the gold standard to assess allograft health and guide immunosuppression management. Liver Transplantation 23 1601-1614 2017 AASLD.
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A retrospective study to compare the use of tacrolimus and cyclosporine in combination with adriamycin in post-transplant liver cancer patients.
Gu, L, Jin, W, Kan, L, Wang, X, Shan, C, Fan, H
Cell biochemistry and biophysics. 2015;(2):565-70
Abstract
The aim of this study was to compare the clinical effect of tacrolimus (TAC) versus cyclosporine (CycA) in post-transplant hepatic cancer patients undergoing adriamycin hydrochloride (ADM) chemotherapy. Patients with advanced hepatic cancer who underwent liver transplant and subsequent therapy between March 2007 and March 2009 in our hospital were selected for this study. All of these patients were treated with chemotherapeutic agent adriamycin, with respect to immunosuppressant, whereas they received either TAC or CycA, and hence represented two groups, TAC and controls, respectively. The short- and long-term outcomes of two therapies, ADM + TAC and ADM + CsA, were compared. The TAC group patients showed improved remission compared to the control group (40 cases with 46.0 % versus 32 cases with 31.1 % remission, respectively). The 5-year survival in TAC group was significantly prolonged (20.7 %) compared to that of the controls (8.7 %). The short-term outcomes, such as serum levels of calcium, biomarkers of cardiac toxicity/functioning, and regulatory T lymphocytes counts (markers of immune functioning), were found to be significantly more auspicious with TAC treatment than with CycA. Our study showed that use of TAC plus ADM resulted in improved patient survival, tolerance of the graft, and remission compared to CycA combined with ADM. The serum levels of various markers in the short follow-up analysis indicated a better cardiac and immune functioning with TAC than with CycA treatment.
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Pre- and postoperative immunonutrition in patients undergoing liver transplantation: a pilot study of safety and efficacy.
Plank, LD, McCall, JL, Gane, EJ, Rafique, M, Gillanders, LK, McIlroy, K, Munn, SR
Clinical nutrition (Edinburgh, Scotland). 2005;(2):288-96
Abstract
BACKGROUND & AIMS Malnutrition is common in patients with end-stage liver disease and is a risk factor for post-transplant morbidity. The goal of this study was to assess the safety of an immune-enhancing diet in patients undergoing liver transplantation and to investigate its effects on nutritional status. METHODS Fifteen consecutive patients received oral Impact (0.6l/d) for a median 54 (range 10-168)d pre-transplant and enteral Impact was started early after transplant. Total body protein was measured prior to commencing supplemental Impact, immediately prior to transplant and 10, 15, 30, 90, and 180 days post-transplant. The results were compared with those from 17 patients who received standard nutritional intervention. RESULTS All study patients tolerated Impact pre- and postoperatively and there were no safety concerns. Over the preoperative period total body protein increased significantly (P = 0.017). In 7 patients followed for 6 months post-transplant, a significant (P = 0.026) loss of body protein occurred over the first 15 postoperative days which was regained by 6 months. In the patients who did not receive Impact, body protein did not change preoperatively and the loss after surgery was not regained. Infectious complications occurred in 5/15 (33%) Impact patients and 12/17 (71%) non-Impact patients (P = 0.074). CONCLUSIONS In patients with end-stage liver disease, our results suggest the possibility that Impact may have a role in improving preoperative nutritional status, hastening recovery after transplant, and reducing postoperative infectious complications. These potential benefits need to be confirmed in a randomised controlled trial.