Antibody-mediated rejection of the liver allograft: An update and a clinico-pathological perspective

Role of autophagy in rejection after solid organ transplantation: A systematic review of the literature

Organ transplantation has long been recognized as an effective treatment for end-stage organ failure, metabolic diseases, and malignant tumors. However, graft rejection caused by major histocompatibility complex mismatch remains a significant challenge. While modern immunosuppressants have made significant strides in reducing the incidence and risk of rejection, they have not been able to eliminate it completely. The intricate mechanisms underlying transplant rejection have been the subject of intense investigation by transplant immunologists. Among these factors, autophagy has emerged as a key player. Autophagy is an evolutionarily conserved mechanism in eukaryotic cells that mediates autophagocytosis and cellular protection. This process is regulated by autophagy-related genes and their encoded protein families, which maintain the material and energetic balance within cells. Additionally, autophagy has been reported to play crucial roles in the development, maturation, differentiation, and responses of immune cells. In the complex immune environment following transplantation, the role and mechanisms of autophagy are gradually being revealed. In this review, we aim to explore the current understanding of the role of autophagy in solid organ rejection after transplantation. Furthermore, we delve into the therapeutic advancements achieved by targeting autophagy involved in the rejection process.

Ten years of a pediatric living donor liver transplantation program in Brazil

BACKGROUND

Pediatric living-donor liver transplantation is considered a safe alternative for the treatment of children with end-stage liver disease. Experienced tertiary centers and specialized medical staff are necessary to ensure compatible long-term survival rates and quality-of-life for these children.

AIM

To report the results and the 10-year learning curve of a pediatric living-donor liver transplantation program.

METHODS

We conducted a retrospective cohort study of pediatric recipients from 2013 to 2023. Post-transplant outcomes and patient survival rates were compared between two 5-year periods of the program.

RESULTS

A total of 25 and 48 patients underwent transplantation in the first (2013-2017) and second period (2018-2023), respectively. Portal vein and hepatic artery thrombosis occurred in 11 (15.1%) and seven (9.6%) patients, respectively. Biliary complications were observed in 39 of 73 patients (53.4%). A lower warm ischemia time was observed in the second period compared to the first (32.6 ± 8.6 minutes vs 38.4 ± 9.8 minutes, P = 0.018, respectively). Patient survival rates at 1 and 5 years were 84% in the first period and 91.7% in the second period, with no significant difference (P = 0.32).

CONCLUSION

The reported indications and outcomes align with the current literature. Our findings provide crucial evidence regarding the feasibility of establishing a living donor program with consistent results over time.

Combined use of Carfilzomib and plasmapheresis in antibody-mediated liver transplant rejection

Antibody-mediated rejection (AMR) poses significant challenges in liver transplant patients, and treatment guidelines recommend variable approaches which usually combine therapeutic plasma exchange (TPE) with immunosuppression therapies without standardized protocols [1]. Here we report two patients with AMR post-liver transplant refractory to multiple treatment regimens who were consequently treated with a combination of Carfilzomib and TPE. Patient 1 was treated within two months after transplant and demonstrated significant clinical improvement, normalization of liver function tests (LFTs) and bilirubin, and reduction in donor-specific antibody (DSA) levels following Carfilzomib and TPE. Conversely, Patient 2 was treated more than seven months after the transplant and additionally suffered from chronic cellular rejection with intermittent adherence to outpatient immunosuppressive medications; although DSA levels were marginally reduced following Carfilzomib and TPE, the patient showed minimal clinical improvement, ultimately necessitating a repeat transplant. Overall, Case #1 suggests that Carfilzomib combined with TPE can improve outcomes in select patients especially who have early AMR, while Case #2 highlights critical complicating factors including concomitant disease processes and immunosuppression, thus emphasizing the need for personalizing treatment strategies based on clinical presentation.

Pediatric Liver Transplant Pathology: An Update and Practical Consideration

This review provides a summary of the diagnostic approach to pediatric liver transplantation (LT) pathology. It emphasizes the pathologic features of T-cell-mediated rejection, the most common finding on liver allograft biopsies, and discusses other forms of rejection, including the less frequent antibody-mediated rejection. The article incorporates insights from the recently published Banff 2022 Liver Group Meeting Report. Additionally, it covers other complications such as biliary and vascular issues, infections, and disease recurrence. Finally, the review summarizes the potential applications of novel technologies, including next-generation pathology and artificial intelligence, in the context of pediatric LT pathology.

Diagnostic and predictive biomarkers of acute rejection after liver transplantation

Liver transplantation serves as a vital therapeutic intervention for individuals suffering from end-stage liver disease globally. A significant complication encountered by liver transplant recipients during the postoperative period is acute rejection, which has traditionally been identified through invasive graft biopsy procedures. Furthermore, assessing the immune status of liver transplant patients is essential for effective posttransplant management and represents a significant advancement toward the personalization of immunosuppressive therapy. Nevertheless, current immunological monitoring after the transplantation predominantly depends on clinical judgment and the measurement of immunosuppressive drug levels, lacking a comprehensive evaluation of actual immune system suppression. In contrast, biomarkers offer a comparatively novel and safer approach for the detection and prediction of transplant rejection, though their clinical application remains constrained due to the absence of prospective validation studies. This review examines the existing literature on potential biomarkers for acute rejection following liver transplantation, and their implications for clinical decision-making.

Cross-organ hierarchy of HLA molecular mismatches in donor-specific antibody development in solid organ transplantations

Donor-specific antibodies (DSAs) against human leukocyte antigen (HLA) play a crucial role in antibody-mediated rejection, a major barrier to successful organ transplantation. Donor-recipient HLA molecular incompatibility critically influences DSA susceptibility, commonly assessed by analyzing mismatches in the HLA eplet repertoire. This study, including six distinct liver, lung, and kidney transplant cohorts from two centers (978 donor-recipient pairs), explores associations between individual eplet mismatches and DSA development. Certain mismatched eplets are strongly linked to DSA development, while others show weaker associations, a trend consistent across different organ types. Machine learning leverages these hierarchical associations to develop an eplet risk score (ERS), outperforming traditional eplet mismatch assessments. Furthermore, T cell proliferation in mixed lymphocyte reaction in vitro correlates with the ERS, attenuated by antibody-mediated inhibition of a mismatched DSA-associated eplet. These results establish the differential immunological impacts of mismatched HLA eplets as integral in clinical practice and therapeutic innovation.

Clinical Features and Treatment of Antibody-Mediated Rejection After Liver Transplantation: A Largest Single Center Experience in China

Antibody-mediated rejection (AMR) is frequently observed in renal transplantation but remains rare and less understood in liver transplantation (LT). This study summarizes the clinical features of AMR in liver transplant patients at our center from August 2020 to October 2023. Thirteen patients were identified as having AMR, including 11 pediatric cases with a median age of 16.2 months. The median interval from transplantation to AMR diagnosis was 54.13 months. Most patients exhibited mild elevation in liver function. A notable decrease in CD4+ T cells was found in acute AMR patients, alongside reduced complement C3 in chronic cases. PRA was positive in 92.31% of patients, all of whom had elevated class II DSA. Additionally, many patients experienced infections with non-hepatotropic viruses. Following intensified immunosuppression and other therapies, 92.31% of patients achieved normal liver function, including five chronic AMR cases with characteristic histological features and seven acute AMR cases that showed no inflammation or centrilobular fibrosis on biopsy. These findings indicate that AMR patients may not exhibit significant liver function abnormalities, emphasizing the critical role of PRA and DSA in diagnosis. The observed reduction in CD4+ T cells and complement C3 may provide valuable insights into the pathogenesis of AMR.

Prediction model of the T cell-mediated rejection after liver transplantation in children and adults: A case-controlled study

OBJECTIVE

T cell-mediated rejection (TCMR) is a major concern following liver transplantation (LT), and identifying its predictors could help improve post-transplant prognosis. This study aimed to develop a model to predict the risk of TCMR in children and adults after LT.

METHOD

Pre-transplant demographic characteristics, intraoperative parameters, and especially early post-transplant laboratory data for 1221 LT recipients (1096 adults and 125 children) were obtained from the Hospital, University, between 1 January 2015, and 1 January 2022. These data were analyzed to develop the prediction model.

RESULT

The incidence of TCMR was higher in pediatric LT recipients than in adults (17.6% vs. 6.4%, P < 0.001). In adult recipients, seven predictors were identified: donor sex, recipient age, recipient height, and post-transplant levels of serum direct bilirubin, urea, platelets, and neutrophil-to-lymphocyte ratio. In pediatric recipients, four predictors were identified: post-transplant levels of serum monocyte percentage, direct bilirubin, albumin, and gamma-glutamyl transferase. The area under the model's curve incorporating these variables for predicting TCMR after LT was 0.713 (95% confidence interval, CI: 0.655-0.770) in adults and 0.786 (95% CI: 0.675-0.896) in children. Decision curve analyses demonstrated the clinical significance of the model.

CONCLUSION

This study developed a prediction model that may be useful in identifying high-TCMR-risk populations in both adult and pediatric LT recipients.

METTL3 Potentiates M2 Macrophage-Driven MMT to Aggravate Renal Allograft Fibrosis via the TGF-β1/Smad3 Pathway

METTL3, a key enzyme in N6-methyladenosine (m6A) modification, plays a crucial role in the progression of renal fibrosis, particularly in chronic active renal allograft rejection (CAR). This study explored the mechanisms by which METTL3 promotes renal allograft fibrosis, focusing on its role in the macrophage-to-myofibroblast transition (MMT). Using a comprehensive experimental approach, including TGF-β1-induced MMT cell models, METTL3 conditional knockout (METTL3 KO) mice, and renal biopsy samples from patients with CAR, the study investigates the involvement of METTL3/Smad3 axis in driving MMT and renal fibrosis during the episodes of CAR. We found that elevated m6A modification and METTL3 levels strongly correlated with enhanced MMT and increased fibrotic severity. METTL3 knockout (METTL3 KO) significantly increased the m6A modification of Smad3, decreased Smad3 expression, and inhibited M2-driven MMT. Smad3 knockdown with siRNA (siSmad3) further inhibited M2-driven MMT, while Smad3 overexpression rescued the inhibitory effects of METTL3 silencing, restoring M2-driven MMT and fibrotic tissue damage. Additionally, the METTL3 inhibitor STM2457 effectively reversed M2-driven MMT and alleviated fibrotic tissue damage in CAR. These findings highlight that METTL3 enhances M2-driven MMT in renal fibrosis during CAR by promoting the TGF-β1/Smad3 axis, suggesting that METTL3 is a promising therapeutic target for mitigating renal fibrosis in CAR.

Understanding immunological insights of liver transplantation: a practice for attaining operational tolerance

Liver transplantation has been at the forefront of medical research, with efforts concentrated on understanding the intricate cellular and molecular dynamics involved this complex procedure. This body of work has chronicled critical clinical advancements, identified challenges, and highlighted progressive improvements in surgical practices. These concerted efforts have significantly contributed to the evolution and enhancement of liver transplantation, elevating it to its current level of sophistication. A successful liver transplant now demands an integrated, multidisciplinary approach that includes not only expanding the donor pool from deceased to living donors but also embracing advances in surgical methods, efficiently managing post-transplant complications, and, importantly, achieving operational tolerance. The latter, operational tolerance, is a state wherein the recipient's immune system is coaxed into accepting the transplanted organ without the long-term use of immunosuppressive drugs, thereby minimizing potential side effects, and improving quality of life. Understanding the critical immune mechanisms that aim to prevent graft rejection is essential from an immunological perspective. This review aims to highlight the crucial areas of host versus graft immune responses, making a clear distinction between organs received from living and deceased donors. It examines how these immune responses, both innate and adaptive, are initiated and proposes the exploration of molecular docking sites as a strategy to curb unwanted immune reactions. Additionally, this review explores the promising potential of biomarkers in predicting graft rejection, and emphasizes the importance of achieving tolerance and the continuous quest for innovative strategies to enhance the success and longevity of liver transplants.

Human leukocyte antigen and donor-specific antibodies in liver transplantation

In this article, we comment on an article published in a recent issue of the World Journal of Gastroenterology. We specifically focus on the roles of human leukocyte antigen (HLA) and donor-specific antibodies (DSAs) in pediatric liver transplantation (LT), as well as the relationship between immune rejection after LT and DSA. Currently, LT remains the standard of care for pediatric patients with end-stage liver disease or severe acute liver failure. However, acute and chronic rejection continues to be a significant cause of graft dysfunction and loss. HLA mismatch significantly reduces graft survival and increases the risk of acute rejection. Among them, D→R one-way mismatch at three loci was significantly related to graft-versus-host disease incidence after LT. The adverse impact of HLA-DSAs on LT recipients is already established. Therefore, the evaluation of HLA and DSA is crucial in pediatric LT.

Defining an NK Cell-enriched Rejection-like Phenotype in Liver Transplant Biopsies From the INTERLIVER Study

BACKGROUND

Initial analysis of liver transplant biopsies in the INTERLIVER study (ClinicalTrials.gov; unique identifier NCT03193151) using rejection-associated transcripts failed to find an antibody-mediated rejection state (ie, rich in natural killer [NK] cells and with interferon-gamma effects). We recently developed an optimization strategy in lung transplants that isolated an NK cell-enriched rejection-like (NKRL) state that was molecularly distinct from T cell-mediated rejection (TCMR). Here we apply the same strategy to a liver transplant biopsy population.

METHODS

We used this strategy to search for a molecular NKRL state in 765 consented liver transplant biopsies collected at participating international centers for gold-standard histology and molecular assessment by genome-wide microarrays. Validation through a training set-test set approach of an optimized selection of variables as inputs into unsupervised rejection classification identified an NKRL state in livers.

RESULTS

The full model classified 765 biopsies into the following molecular phenotypes, characterized by their gene expression: no-rejection 54%, TCMR 16%, NKRL 13%, and injury 16%. Top TCMR transcripts were expressed in effector T cells; top NKRL transcripts were almost exclusively expressed in NK cells; and both had increased interferon-γ-inducible transcripts, which were more pronounced in TCMR. Most TCMR biopsies had significant parenchymal injury, molecular fibrosis, and abnormal biochemistry. NKRL biopsies had no excess of injury, fibrosis, or biochemistry abnormalities.

CONCLUSIONS

Optimized rejection algorithms indicate that some liver transplants manifest an NKRL state that is well tolerated in the short term postbiopsy and with minimal injury and relatively normal biochemistry, while also underscoring the potential of TCMR to produce extensive parenchymal injury.

Post-transplant liver biopsies: a concise and practical approach for beginners

Exposure to post-transplant liver biopsies varies among pathology residencies and largely depends on the institution's training program, particularly if the hospital has a liver transplant program. The interpretation of biopsies from transplanted livers presents its own set of challenges, even for those with a solid understanding of non-transplant medical liver biopsies. In this review, we aim to provide a succinct, step-by-step approach to help you interpret liver transplant biopsies. This article may be beneficial for residents interested in liver pathology, gastrointestinal and liver pathology fellows in the early stages of training, clinical gastroenterology and hepatology fellows, hepatologists and general pathologists who are curious about this niche.

Network meta-analysis of pharmacological treatment for antibody-mediated rejection after organ transplantation

Objective

This study aims to assess the efficacy of pharmacological interventions in mitigating graft injury in transplant patients with antibody-mediated rejection (AMR) through a network meta-analysis (NMA).

Methods

A search was conducted on databases such as Cochrane Library, PubMed, EmBase, and Web of Science for randomized controlled trials (RCTs) on pharmacological interventions for alleviating graft injury following AMR. The search was performed for publications up to April 12, 2024. Two reviewers conducted independent reviews of the literature, extracted data, and assessed the risk of bias (ROB) in the included studies using the ROB assessment tool recommended by the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0. A Bayesian NMA was conducted using R 4.4.0, RStudio software, and the GeMTC package to assess the outcomes in estimated glomerular filtration rate (eGFR), mean fluorescence intensity (MFI), g-score, and infection under pharmacological treatments.

Results

A total of 8 RCTs involving 215 patients and 6 different pharmacological treatments were included in this NMA. The results indicated that the increase in eGFR by eculizumab (SUCRA score: 81) appeared to be more promising. The decrease in MFI by bortezomib (SUCRA score: 72.3), rituximab (SUCRA score: 68.2), and clazakizumab (SUCRA score: 67.1) demonstrated better efficacy. The decrease in g-score by eculizumab (SUCRA score: 74.3), clazakizumab (SUCRA score: 72.2), and C1INH (SUCRA score: 63.6) appeared to have more likelihood. For infection reduction, clazakizumab (SUCRA score: 83.5) and bortezomib (SUCRA score: 66.8) might be better choices.

Conclusion

The results of this study indicate that eculizumab has the potential to enhance eGFR and reduce g-score. Bortezomib demonstrates superior efficacy in reducing MFI. Clazakizumab appears to be more effective in reducing infections.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024546483.

Incidence, clinical classification and risk factors of cyclosporin A-induced liver injury in allogeneic haematopoietic stem cell transplant recipients

AIMS

There is limited real-world data on cyclosporin A (CsA)-induced liver injury (CILI). This study aims to investigate the incidence, clinical classification and risk factors of CILI, thereby providing evidence to inform the treatment of CILI.

METHODS

Inpatients receiving haematopoietic stem cell transplantation (HSCT) and treated with CsA were included. Patient information was collected to assess suspicious CILI by the Roussel Uclaf causality assessment method (RUCAM) scale. We evaluated the pattern and severity of CILI. The independent risk factors of CILI were identified by multivariable logistic regression.

RESULTS

A total of 216 allogeneic HSCT (allo-HSCT) recipients were included in this study. The incidence of CILI was 15.3% (95% confidence interval [CI]: 10.4%-20.1%). Among these cases, 84.8% displayed a hepatocellular pattern, and 90.9% of CILI was of mild severity. Baseline alanine aminotransferase (ALT) level (OR = 1.030, 95% CI: 1.008-1.053, P = .008) and trough concentration level of CsA (OR = 1.007, 95% CI: 1.002-1.012, P = .009) were identified as independent risk factors for CILI.

CONCLUSIONS

The incidence of CILI in allo-HSCT recipients is notably high. Recipients with elevated baseline ALT levels and higher exposure to CsA are more susceptible to developing CILI.

Human leukocyte antigen compatibility and incidence of donor-specific antibodies in pediatric liver transplant recipients

BACKGROUND

Antibody-mediated rejection following liver transplantation (LT) has been increasingly recognized, particularly with respect to the emergence of de novo donor-specific antibodies (DSAs) and their impact on graft longevity. While substantial evidence for adult populations exists, research focusing on pediatric LT outcomes remains limited.

AIM

To investigate the prevalence of human leukocyte antigen (HLA) mismatches and DSA and evaluate their association with rejection episodes after pediatric LT.

METHODS

A cohort of pediatric LT recipients underwent HLA testing at Santa Casa de Porto Alegre, Brazil, between December 2013 and December 2023. Only patients who survived for > 30 days after LT with at least one DSA analysis were included. DSA classes I and II and cross-matches were analyzed. The presence of de novo DSA (dnDSA) was evaluated at least 3 months after LT using the Luminex® single antigen bead method, with a positive reaction threshold set at 1000 MFI. Rejection episodes were confirmed by liver biopsy.

RESULTS

Overall, 67 transplanted children were analyzed; 61 received grafts from living donors, 85% of whom were related to recipients. Pre-transplant DSA (class I or II) was detected in 28.3% of patients, and dnDSA was detected in 48.4%. The median time to DSA detection after LT was 19.7 [interquartile range (IQR): 4.3-35.6] months. Biopsy-proven rejection occurred in 13 patients at follow-up, with C4d positivity observed in 5/13 Liver biopsies. The median time to rejection was 7.8 (IQR: 5.7-12.8) months. The presence of dnDSA was significantly associated with rejection (36% vs 3%, P < 0.001). The rejection-free survival rates at 12 and 24 months were 76% vs 100% and 58% vs 95% for patients with dnDSA anti-DQ vs those without, respectively.

CONCLUSION

Our findings highlight the importance of incorporating DSA assessment into pre- and post-transplantation protocols for pediatric LT recipients. Future implications may include immunosuppression minimization strategies based on this analysis in pediatric LT recipients.

Antibody-Mediated Rejection in Liver Transplantation: Immuno-Pathological Characteristics and Long-Term Follow-Up

The diagnosis of liver antibody-mediated rejection (AMR) is challenging and likely under-recognized. The association of AMR with donor-specific antibodies (DSA), and its clinical course in relation to pathologic findings and treatment are ill defined. We identified cases of liver AMR by following the criteria outlined by the 2016 Banff Working Group. Patient demographics, native liver disease, histopathologic findings, treatment type, clinical outcome, and transaminase levels during AMR diagnosis, treatment, and resolution were determined. Patients (n = 8) with AMR average age was 55.2 years (range: 19-68). Seven of eight cases met the Banff criteria for AMR. Personalized treatment regimens consisted of optimization of immunosuppression, intravenous pulse steroids, plasmapheresis, IVIG, rituximab, and bortezomib. Five patients experienced complete resolution of AMR, return of transaminases to baseline, and decreased DSA at long-term follow-up. One patient developed chronic AMR and two patients required re-transplantation. Follow-up after AMR diagnosis ranged from one to 11 years. Because AMR can present at any time, crossmatch, early biopsy, and routine monitoring of DSA levels should be implemented following transaminase elevation to recognize AMR. Furthermore, treatment should be immediately implemented to reverse AMR and prevent graft failure, chronic damage, re-transplantation, and possibly mortality.

Computational identification of novel potential genetic pathogenesis and otherwise biomarkers in acute liver allograft rejection

Acute cellular rejection (ACR) is a prevalent postoperative complication following liver transplantation (LT), exhibiting an increasing incidence of morbidity and mortality. However, the molecular mechanisms of ACR following LT remain unclear. To explore the genetic pathogenesis and identify biomarkers of ACR following LT, three relevant Gene Expression Omnibus (GEO) datasets consisting of data on ACR or non-ACR patients after LT were comprehensively investigated by computational analysis. A total of 349 upregulated and 260 downregulated differentially expressed genes (DEGs) and eight hub genes (ISG15, HELZ2, HNRNPK, TIAL1, SKIV2L2, PABPC1, SIRT1, and PPARA) were identified. Notably, HNRNPK, TIAL1, and PABPC1 exhibited the highest predictive potential for ACR with AUCs of 0.706, 0.798, and 0.801, respectively. KEGG analysis of hub genes revealed that ACR following LT was predominately associated with ferroptosis, protein processing in the endoplasmic reticulum, complement and coagulation pathways, and RIG-I/NOD/Toll-like receptor signaling pathway. According to the immune cell infiltration analysis, γδT cells, NK cells, Tregs, and M1/M2-like macrophages had the highest levels of infiltration. Compared to SIRT1, ISG15 was positively correlated with γδT cells and M1-like macrophages but negatively correlated with NK cells, CD4+ memory T cells, and Tregs. In conclusion, this study identified eight hub genes and their potential pathways, as well as the immune cells involved in ACR following LT with the greatest levels of infiltration. These findings provide a new direction for future research on the underlying mechanism of ACR following LT.

Nanotechnology-based Strategies for Molecular Imaging, Diagnosis, and Therapy of Organ Transplantation

Organ transplantation is the preferred paradigm for patients with end-stage organ failures. Despite unprecedented successes, complications such as immune rejection, ischemia-reperfusion injury, and graft dysfunction remain significant barriers to long-term recipient survival after transplantation. Conventional immunosuppressive drugs have limited efficacy because of significant drug toxicities, high systemic immune burden, and emergence of transplant infectious disease, leading to poor quality of life for patients. Nanoparticle-based drug delivery has emerged as a promising medical technology and offers several advantages by enhancing the delivery of drug payloads to their target sites, reducing systemic toxicity, and facilitating patient compliance over free drug administration. In addition, nanotechnology-based imaging approaches provide exciting diagnostic methods for monitoring molecular and cellular changes in transplanted organs, visualizing immune responses, and assessing the severity of rejection. These noninvasive technologies are expected to help enhance the posttransplantation patient survival through real time and early diagnosis of disease progression. Here, we present a comprehensive review of nanotechnology-assisted strategies in various aspects of organ transplantation, including organ protection before transplantation, mitigation of ischemia-reperfusion injury, counteraction of immune rejection, early detection of organ dysfunction posttransplantation, and molecular imaging and diagnosis of immune rejection.

Rejection in Liver Transplantation Recipients

Rejection following liver transplantation continues to impact transplant recipients although rates have decreased over time with advances in immunosuppression management. The diagnosis of rejection remains challenging with liver biopsy remaining the reference standard for diagnosis. Proper classification of rejection type and severity is imperative as this guides management and ultimately graft preservation. Future areas of promise include non-invasive testing for detection of rejection to reduce the morbidity associated with invasive testing and further advances in immunosuppression management to reduce toxicities associated with immunosuppression while minimizing rejection related morbidity.

Identification of liver transplant biopsy phenotypes associated with distinct liver biological markers and allograft survival

The intricate association between histologic lesions and circulating antihuman leucocyte antigen donor-specific antibodies (DSA) in liver transplantation (LT) requires further clarification. We conducted a probabilistic, unsupervised approach in a comprehensively well-annotated LT cohort to identify clinically relevant archetypes. We evaluated 490 pairs of LT biopsies with DSA testing from 325 recipients transplanted between 2010 and 2020 across 3 French centers and an external cohort of 202 biopsies from 128 recipients. Unsupervised archetypal analysis integrated all clinico-immuno-histologic parameters of each biopsy to identify biopsy archetypes. The median time after LT was 1.17 (interquartile range, 0.38-2.38) years. We identified 7 archetypes distinguished by clinico-immuno-histologic parameters: archetype #1: severe T cell-mediated rejection (15.9%); #2: chronic rejection with ductopenia (1.8%); #3: architectural and microvascular damages (3.5%); #4: (sub)normal (55.9%); #5: mild T cell-mediated rejection (4.9%); #6: acute antibody-mediated rejection (6.5%); and #7: chronic rejection with DSA (11.4%). Cell infiltrates vary in the archetype. These archetypes were associated with distinct liver biological markers and allograft outcomes. These findings remained consistent when stratified using the patient's age or indications for LT, with good performance in the external cohort (mean highest probability assignment = 0.58, standard deviation ± 0.17). In conclusion, we have identified clinically meaningful archetypes, providing valuable insights into the intricate DSA-histology association, which may help standardize liver allograft pathology classification.

Basics and Art of Immunosuppression in Liver Transplantation

Liver transplantation is one of the most challenging areas in the medical field. Despite that, it has already been established as a standard treatment option, especially in decompensated cirrhosis and selected cases of hepatocellular carcinoma and acute liver failure. Complications due to graft rejection, including mortality and morbidity, have greatly improved over time due to better immunosuppressive agents and management protocols. Currently, immunosuppression in liver transplant patients makes use of the best possible combinations of effective agents to achieve optimal immunosuppression for long-term graft survival. Induction agents are no longer used routinely, and the aim is to provide minimal immunosuppression in the maintenance phase. Currently available immunosuppressive agents are mainly classified as biological and pharmacological agents. Though the protocols may vary among the centers and over time, the basics of effective use usually remain similar. Most protocols use the combination of multiple agents with different mechanisms of action to reduce the dose and minimize the side effects. Along with the improvement in operative and perioperative techniques, this art of immunosuppression has contributed to the recent progress made in the outcomes of liver transplants. In this review, we will discuss the various types of immunosuppressive agents currently in use, the different protocols of immunosuppression used, and the art of optimal use for achieving maximum immunosuppression without increasing toxicity. We will also discuss the practical aspects of various immunosuppression regimens, including drug monitoring, and briefly discuss the concepts of immunosuppression minimization and withdrawal.

miRNA as potential biomarkers after liver transplantation: A systematic review

BACKGROUND

Liver transplantation is a life-saving therapy for end-stage liver disease patients, but acute cellular rejection (ACR) and graft complications remain significant postoperative challenges. Early and accurate diagnosis is crucial for timely intervention and improved patient outcomes, but their diagnosis rely currently on invasive biopsy sampling, thus prompting the search for non-invasive Biomarkers. MicroRNA (miRNA) have emerged as promising biomarkers in various pathological conditions, and their potential utility in diagnosing acute cellular rejection after liver transplantation has gained significant interest.

METHODS

This systematic review of PubMed, Web of Science, and the ClinicalTrials.gov registry analyzes studies exploring miRNA as biomarkers for ACR and graft dysfunction in liver transplantation (PROSPERO ID CRD42023465278). The Cochrane Collaboration tool for assessing risk of bias was employed. Population data, identified miRNA and their dynamic regulation, as well as event prediction were compared. Data extraction and quality assessment were performed independently by two reviewers.

RESULTS

Thirteen studies were included in this systematic review. Various investigated miRNAs were upregulated in association with acute cellular rejection, like miR-122, miR-155, miR-181, miR-483-3p, and miR-885-5p, demonstrating great biomarker potential. Additionally, several studies conducted target gene analysis, revealing insights into cellular mechanisms linked to ACR. Moreover, various miRNA were also capable of predicting different organ complications following transplantation, expanding their versatility. Remaining challenges include the standardization of miRNA profiling, the need for functional validation, and the necessity for long-term studies.

CONCLUSION

The results highlight the potential of miRNA as specific, non-invasive biomarkers for ACR and graft dysfunction following liver transplantation. However, further research is needed to validate these findings and establish standardized diagnostic panels to incorporate them into clinical practice and explore miRNA-based therapies in the future.

Immunology demystified: A guide for transplant hepatologists

Liver transplantation has become standard practice for treating end-stage liver disease. The success of the procedure relies on effective immunosuppressive medications to control the host's immune response. Despite the liver's inherent capacity to foster tolerance, the early post-transplant period is marked by significant immune reactivity. To ensure favorable outcomes, it is imperative to identify and manage various rejection types, encompassing T-cell-mediated, antibody-mediated, and chronic rejection. However, the approach to prescribing immunosuppressants relies heavily on clinical judgment rather than evidence-based criteria. Given that the majority of patients will require lifelong immuno suppression as the mechanisms underlying operational tolerance are still being investigated, healthcare providers must possess an understanding of immune responses, rejection mechanisms, and the pathways targeted by immunosuppressive drugs. This knowledge enables customization of treatments and improved patient care, even though a consensus on an optimal immunosuppressive regimen remains elusive.

HLA matching between donors and recipients improves clinical liver transplant graft survival

BACKGROUND AND AIMS

The importance of human leukocyte antigen (HLA) matching between liver transplant donors and recipients on graft survival remains unclear and is not a clinical consideration in liver transplantation. This study aimed to determine the relationship between HLA matching and liver graft survival using a large-scale multi-centre database (UNOS/OPTN) and multivariate logistic analysis. The secondary aim was to determine whether this relationship was influenced by transplant indication and donor status.

METHODS

This retrospective observational analysis was performed using 22 702 liver transplant recipients from the UNOS/OPTN database. Patients were divided into two groups based on number of HLA mismatches (0-3 mismatches vs. 4-6 mismatches) and then subcategorized by indication and donor status. Risk-adjusted outcomes were assessed by multivariate Cox analysis adjusting for donor and recipient characteristics and visualized using Kaplan-Meier survival curves.

RESULTS

Allograft survival and risk of acute rejection were associated with degree of HLA mismatch. This association between HLA mismatch and graft survival persisted in individuals who underwent transplant for hepatitis, metabolic, drug toxicity, and congenital indications. Donor status also influenced the relationship between HLA mismatch and graft survival. Graft survival in DBD recipients was longer than in DCD in the 4-6 HLA mismatch group, whereas no significant difference was found in the 0-3 HLA mismatch group.

CONCLUSION

HLA mismatch significantly reduced graft survival and increased risk of acute rejection. This association was noted only in specific indications. These findings are of potential clinical relevance to organ allocation, allograft matching algorithms, immunosuppression protocols, and transplant surveillance.

Post-Transplant Management and Complications of Autoimmune Hepatitis, Primary Biliary Cholangitis, and Primary Sclerosing Cholangitis including Disease Recurrence

Autoimmune liver diseases have unique post-transplant considerations. These recipients are at increased risk of rejection, and recurrent disease may also develop, which can progress to graft loss and increase mortality. Monitoring for and managing these complications is therefore important, though data on associated risk factors and immunosuppression strategies has in most cases been mixed. There are also other disease-specific complications that require management and may impact these decisions, including inflammatory bowel disease in PSC. Further work to better understand the optimal management strategies for these patients post-transplant is needed.

Current Use of Immunosuppression in Liver Transplantation

Since the first successful liver transplant in 1967, immunosuppression has allowed liver transplantation to become the standard treatment of end-stage liver disease. Over the decades, the rates of rejection have decreased, and patient survival outcomes have significantly improved in large part due to the introduction and advancements of immunosuppression medications. However, the adverse effects associated with long-term immunosuppression have created new challenges facing liver transplantation and added significantly to posttransplantation morbidity. This review presents the data and rationale for immunosuppression approaches, addresses the main controversies related to immunosuppression in liver transplantation, and explores some of the newer advancements in immunosuppressive drug therapy.

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Balancing immunosuppression in pediatric liver transplantation: Playing the long game

The overarching goal in the care of pediatric liver transplant recipients is to optimize allograft and patient health. Balancing immunosuppression to maintain allograft health while avoiding medication side effects is essential for long-term survival and optimal quality of life in pediatric liver transplant recipients. Utilizing precision medicine to personalize immunosuppression, which includes minimization and withdrawal, is core to this effort. The unique anatomy and physiology of the liver make it more tolerant to immune-mediated injury and a more favorable organ for immunosuppression minimization and withdrawal. However, several challenges exist. Standard biochemical values and histologic features may not reliably predict allograft health after a reduction in immunosuppression. Additionally, biochemical values alone do not reliably identify which patients can successfully develop operational tolerance, as there may be occult allograft injury despite normal liver enzymes. Finally, the durability of tolerance after successful reduction in immunosuppression remains uncertain over time. Innovative tools show promise in circumventing these challenges, but more research is needed to determine actual clinical utility. While immunosuppression-free transplant may not be a current reality for most pediatric liver transplant recipients, strategies to safely minimize immunosuppression without compromising allograft health are within reach. Each liver allograft and recipient pair requires a different degree of immune modulation, and through a structured process of minimization and withdrawal, immunosuppression can indeed be tailored in a precise, personalized way to optimize outcomes. This review focuses on the progress that has been made to individualize immunosuppression in pediatric liver transplantation to ensure optimal allograft and recipient health.

Recent advances in understanding T cell activation and exhaustion during HBV infection

Chronic hepatitis B virus (HBV) infection remains a major public health concern globally, and T cell responses are widely believed to play a pivotal role in mediating HBV clearance. Accordingly, research on the characteristics of HBV-specific T cell responses, from activation to exhaustion, has advanced rapidly. Here, we summarize recent developments in characterizing T cell immunity in HBV infection by reviewing basic and clinical research published in the last five years. We provide a comprehensive summary of the mechanisms that induce effective anti-HBV T cell immunity, as well as the latest developments in understanding T cell dysfunction in chronic HBV infection. Furthermore, we briefly discuss current novel treatment strategies aimed at restoring anti-HBV T cell responses.

Treatment of donor-specific anti-HLA antibodies-mediated rejection after liver transplantation: A French nationwide retrospective study

The deleterious effect of donor-specific anti-HLA antibodies (DSA) after liver transplantation (LT) has been increasingly recognized during the past decade. Antibody-mediated rejection (AMR) represents a rare but severe complication in the presence of DSA. However, little is known concerning the treatment of AMR after LT. The nationwide French study aimed to describe LT recipients who received specific treatment of AMR. We performed a multicenter retrospective study on 44 patients who were treated with B-cell targeting agents from January 2008 to December 2020. Median patient age at the time of AMR treatment was 51.6 years (range: 17.9-68.0). AMR was classified as acute (n = 19) or chronic (n = 25). The diagnosis of AMR was made after a median time of 16.8 months (range: 0.4-274.2) after LT. The main therapeutic combination was plasma exchange/rituximab/IVIG (n = 25, 56.8%). The median follow-up after the treatment of AMR was 32 months (range: 1-115). After the treatment, 1-, 5- and 10-year patient and graft survivals were 77%, 55.9%, and 55.9%, and 69.5%, 47.0%, and 47.0%, respectively. Initial total bilirubin (Q1-Q3 vs. Q4) was significantly associated with patient survival (log-rank test, p = 0.005) and graft survival (log-rank test, p = 0.002). After a median follow-up of 21 months (range: 12-107), DSA became undetectable in 15/38 patients (39.5%) with available DSA monitoring. In conclusion, specific treatment of AMR in LT recipients has slowly emerged in France during the past decade and has probably been considered in the most severe patients; this explains the global poor outcome, even if the outcome was favorable in some cases.

Immunomodulatory Role of Mesenchymal Stem Cells in Liver Transplantation: Status and Prospects

BACKGROUND

Liver transplantation (LT) is the only effective therapy for end-stage liver diseases, but some patients usually present with serious infection and immune rejection. Those with immune rejection require long-term administration of immunosuppressants, leading to serious adverse effects. Mesenchymal stem cells (MSCs) have various advantages in immune regulation and are promising drugs most likely to replace immunosuppressants.

SUMMARY

This study summarized the application of MSCs monotherapy, its combination with immunosuppressants, MSCs genetic modification, and MSCs derivative therapy (cell-free therapy) in LT. This may deepen the understanding of immunomodulatory role of MSCs and promote the application of MSCs in immune rejection treatment after LT.

KEY MESSAGES

MSCs could attenuate ischemia-reperfusion injury and immune rejection. There is no consensus on the effects of types and concentrations of immunosuppressants on MSCs. Although genetically modified MSCs have contributed to better outcomes to some extent, the best modification is still unclear. Besides, multiple clinical complications developed frequently after LT. Unfortunately, there are still few studies on the polygenic modification of MSCs for the simultaneous treatment of these complications. Therefore, more studies should be performed to investigate the potency of multi-gene modified MSCs in treating complications after LT. Additionally, MSC derivatives mainly include exosomes, extracellular vesicles, and conditioned medium. Despite therapeutic effects, these three therapies still have some limitations such as heterogeneity between generations and that they cannot be quantified accurately.

Liver transplantation immunology: Immunosuppression, rejection, and immunomodulation

Outcomes after liver transplantation have continuously improved over the past decades, but long-term survival rates are still lower than in the general population. The liver has distinct immunological functions linked to its unique anatomical configuration and to its harbouring of a large number of cells with fundamental immunological roles. The transplanted liver can modulate the immunological system of the recipient to promote tolerance, thus offering the potential for less aggressive immunosuppression. The selection and adjustment of immunosuppressive drugs should be individualised to optimally control alloreactivity while mitigating toxicities. Routine laboratory tests are not accurate enough to make a confident diagnosis of allograft rejection. Although several promising biomarkers are being investigated, none of them is sufficiently validated for routine use; hence, liver biopsy remains necessary to guide clinical decisions. Recently, there has been an exponential increase in the use of immune checkpoint inhibitors due to the unquestionable oncological benefits they provide for many patients with advanced-stage tumours. It is expected that their use will also increase in liver transplant recipients and that this might affect the incidence of allograft rejection. Currently, the evidence regarding the efficacy and safety of immune checkpoint inhibitors in liver transplant recipients is limited and cases of severe allograft rejection have been reported. In this review, we discuss the clinical relevance of alloimmune disease, the role of minimisation/withdrawal of immunosuppression, and provide practical guidance for using checkpoint inhibitors in liver transplant recipients.

Single-cell RNA-seq revealing the immune features of donor liver during liver transplantation

Immune cells, including T and B cells, are key factors in the success of liver transplantation. And the repertoire of T cells and B cells plays an essential function in mechanism of the immune response associated with organ transplantation. An exploration of their expression and distribution in donor organs could contribute to a better understanding of the altered immune microenvironment in grafts. In this study, using single-cell 5' RNA sequence and single-cell T cell receptor (TCR)/B cell receptor (BCR) repertoire sequence, we profiled immune cells and TCR/BCR repertoire in three pairs of donor livers pre- and post-transplantation. By annotating different immune cell types, we investigated the functional properties of monocytes/Kupffer cells, T cells and B cells in grafts. Bioinformatic characterization of differentially expressed genes (DEGs) between the transcriptomes of these cell subclusters were performed to explore the role of immune cells in inflammatory response or rejection. In addition, we also observed shifts in TCR/BCR repertoire after transplantation. In conclusion, we profiled the immune cell transcriptomics and TCR/BCR immune repertoire of liver grafts during transplantation, which may offer novel strategies for monitoring recipient immune function and treatment of rejection after liver transplantation.

Acute Antibody-Mediated Rejection in Liver Transplant Recipients with Autoimmune Liver Disease: A Clinical and Pathologic Study of 4 Cases

Background: Acute antibody-mediated rejection (AMR) is an uncommon complication after ABO-compatible liver transplantation (LT). This case series investigated the clinicopathologic characteristics and outcomes of acute AMR in LT recipients with autoimmune liver disease (ALD). Patients and Methods: Among 809 patients who underwent LT from January 2014 to December 2020, four ALD patients developed AMR, which was confirmed based on clinical features, histopathology of liver biopsy, donor-specific antibodies (DSA) or panel reactive antibody (PRA) level. Therapies were individualized based on clinical manifestations. Results: The incidence of acute AMR was 0.49%, and the incidence of acute AMR with ALD and non-ALD recipients was 11.1% and 0%, respectively. Three patients had strongly positive HLA class II DSA, and one patient was with the PRA class I and II sensitivities, which were >80%; complement component 4d (C4d) staining was negative in all patients. The first patient underwent re-LT, and the other three patients had good prognoses with treatments. Conclusions: ALD patients are prone to acute AMR after LT, thus should be kept vigilant against the occurrence of acute AMR.

From a Single Cell to a Whole Human Liver: Disease Modeling and Transplantation

Although the underlying cause may vary across countries and demographic groups, liver disease is a major cause of morbidity and mortality globally. Orthotopic liver transplantation is the only definitive treatment for liver failure but is limited by the lack of donor livers. The development of drugs that prevent the progression of liver disease and the generation of alternative liver constructs for transplantation could help alleviate the burden of liver disease. Bioengineered livers containing human induced pluripotent stem cell (iPSC)-derived liver cells are being utilized to study liver disease and to identify and test potential therapeutics. Moreover, bioengineered livers containing pig hepatocytes and endothelial cells have been shown to function and survive after transplantation into pig models of liver failure, providing preclinical evidence toward future clinical applications. Finally, bioengineered livers containing human iPSC-derived liver cells have been shown to function and survive after transplantation in rodents but require considerable optimization and testing prior to clinical use. In conclusion, bioengineered livers have emerged as a suitable tool for modeling liver diseases and as a promising alternative graft for clinical transplantation. The integration of novel technologies and techniques for the assembly and analysis of bioengineered livers will undoubtedly expand future applications in basic research and clinical transplantation.

The New Challenge in Pediatric Liver Transplantation: Chronic Antibody-Mediated Rejection

Antibody-mediated rejection (AMR) of liver allograft transplantation was considered as anecdotal for many decades. However recently, AMR has gained clinical awareness as a potential cause of chronic liver injury, leading to liver allograft fibrosis and eventual graft failure. (1) Methods: Literature on chronic AMR (cAMR) in pediatric post-liver transplant patients was reviewed for epidemiologic data, physiopathology, diagnosis, and treatment approaches. (2) Results: Accurate incidence of cAMR in pediatric liver transplantation remains unknown. Diagnostic criteria of cAMR were suggested by the Banff Working Group in 2016 and are based on standardized histopathological findings, C4d staining pattern, associated with the presence of donor-specific antibodies (DSA). Physio-pathological mechanisms are not clear for the technically difficult-to-obtain animal models reproducing cAMR. Treatment protocols are not established, being limited to case reports and case series, based on experience in ABO incompatible transplantation and kidney transplantation. Immunosuppression compliance with adequate dose adjustment may prevent cAMR. Conversion of Cyclosporine to Tacrolimus may improve pathological findings if treated in early phase. The association of steroids, Mycophenolate Mofetil (MMF) and mTOR inhibitors have shown some synergistic effects. Second-line treatments such as intravenous immunoglobulin (IVIG) and plasma exchange may decrease antibody titers based on ABO incompatible transplant protocols. The use of anti-CD20 (Rituximab) and proteasome inhibitors (Bortezomib) is controversial due to the lack of qualified studies. Therefore, multicenter randomized trials are needed to establish the best therapeutic strategy. In refractory cases, re-transplantation is the only treatment for allograft failure. (3) Conclusions: This literature review collects recent clinical, histopathological, and therapeutical advances of cAMR in liver allograft transplantation of pediatric patients. There are many physio-pathological aspects of cAMR to be clarified. Further efforts with multicenter prospective protocols to manage patients with cAMR are needed to improve its outcome.

Acute Antibody-Mediated Rejection in Liver Transplantation: Impact and Applicability of the Banff Working Group on Liver Allograft Pathology 2016 Criteria

This study was aimed to examine the clinical utility and impact of the 2016 Banff criteria for acute antibody-mediated rejection (acute AMR) in patients with liver transplantation. Among adult patients with donor-specific antibody (DSA) assays performed between 2015 and 2020, cases with proved DSA (mean fluorescent index >2000) and matched liver biopsy available were reviewed. Among 55 patients identified, 28 (51%) had class I DSA, 45 (82%) had class II DSA and 18 (33%) had both. Mild, moderate and severe microvasculitis were observed in 11 (20%), 2 (4%) and 1 (2%) case, respectively. Diffuse immunoreactivity to C4d on portal microvascular endothelia was confirmed in 5 cases (9%), which met the criteria of definite (n=2) or suspicious for acute AMR (n=3). Cases of acute AMR more commonly had class I DSA (100% vs. 46%; p=0.027) or both class I and II DSA (80% vs. 28%; p=0.018) than cases of non-acute AMR. One case of pure acute AMR with veno-occlusion was successfully treated with plasma exchange. The remaining 4 cases had features of combined acute AMR/T cell-mediated rejection (TCMR), and two progressed to ductopenic rejection within 3 weeks. In conclusion, only 9% of DSA-positive patients met the Banff criteria for acute AMR, necessitating careful morphological and immunohistochemical assessments of the allograft biopsies according to the proposed standards. Combined acute AMR/TCMR was more common than isolated acute AMR, and additional AMR in TCMR cases may be associated with rapid progression to ductopenic rejection.

The use of transient elastography in identifying sub-clinical chronic ductopenic rejection in adult liver transplant recipients: A case series

BACKGROUND

Transient elastography has become a standard tool for the accurate non-invasive assessment of liver stiffness and fat content. Liver transplant recipients can develop allograft fibrosis during long-term follow-up despite normal or mildly abnormal liver chemistries. Tapering of immunosuppression in long-term liver transplant survivors is performed relying solely on liver chemistries. It is important to know if underlying liver histology would be abnormal or if rejection was present as this would alter the desire to decrease stable maintenance doses of immunosuppression.

METHODS

We present our experience of five liver transplant recipients who had transient elastography performed prior to consideration of weaning of their immunosuppression.

RESULTS

All five patients showed signs of elevated liver stiffness on transient elastography in the setting of normal to slightly abnormal liver tests with very stable immunosuppressant doses. This prompted the performance of liver biopsies which demonstrated immune-mediated liver injury and thus negated the immunosuppression withdrawal.

CONCLUSION

Transient elastography has utility as a non-invasive method to evaluate allograft health in long-term liver transplant survivors and can be useful in the decision-making process for immunosuppression weaning.