Rejection In Liver Transplantation Research Articles

SARS-CoV-2 RNA detection in Formalin-Fixed Paraffin-Embedded (FFPE) tissue by droplet digital PCR (ddPCR)

BackgroundSARS-CoV-2 is an RNA virus that primarily causes respiratory disease; however, infection of other tissue has been reported. Evaluation of SARS-CoV-2 in tissue specimens may increase understanding of SARS-CoV-2 pathobiology. Materials and MethodsA qualitative test for detection of SARS-CoV-2 in formalin-fixed paraffin-embedded (FFPE) tissues was developed and validated using droplet digital PCR (ddPCR), which has a lower limit of detection than reverse transcription (RT)-qPCR. After extraction of total RNA from unstained FFPE tissue, SARS-CoV-2 nucleocapsid (N1, N2) target sequences were amplified and quantified, along with human RPP30 as a control using the Bio-Rad SARS-CoV-2 ddPCR kit. ResultsSARS-CoV-2 was detected in all 21 known positive samples and none of the 16 negative samples. As few as approximately 5 viral copies were reliably detected. Since January 2021, many tissue types have been clinically tested. Of the 195 clinical specimens, the positivity rate was 35% with placenta and fetal tissue showing the highest percentage of positive cases. ConclusionThis sensitive FFPE-based assay has broad clinical utility with applications as diverse as pregnancy loss and evaluation of liver transplant rejection. This assay will aid in understanding atypical presentations of COVID-19 as well as long-term sequelae.

Neutrophil Extracellular Traps Regulate HMGB1 Translocation and Kupffer Cell M1 Polarization During Acute Liver Transplantation Rejection.

Neutrophil extracellular traps (NETs) play important roles in hepatic ischemic reperfusion injury (IRI) and acute rejection (AR)-induced immune responses to inflammation. After liver transplantation, HMGB1, an inflammatory mediator, contributes to the development of AR. Even though studies have found that HMGB1 can promote NET formation, the correlation between NETs and HMGB1 in the development of AR following liver transplantation has not been elucidated. In this study, levels of serum NETs were significantly elevated in patients after liver transplantation. Moreover, we found that circulating levels of NETs were negatively correlated with liver function. In addition, liver transplantation and elevated extracellular HMGB1 promoted NET formation. The HMGB1/TLR-4/MAPK signaling pathway, which is initiated by HMGB1, participates in NET processes. Moreover, in the liver, Kupffer cells were found to be the main cells secreting HMGB1. NETs induced Kupffer cell M1 polarization and decreased the intracellular translocation of HMGB1 by inhibiting DNase-1. Additionally, co-treatment with TAK-242 (a TLR-4 inhibitor) and rapamycin more effectively alleviated the damaging effects of AR following liver transplantation than either drug alone.

CD80+ dendritic cell derived exosomes inhibit CD8+ T cells through down-regulating NLRP3 expression after liver transplantation

BackgroundGraft-infiltrated dendritic cells (DCs) and CD8+ T lymphocytes are closely related with immune regulation after liver transplantation (LT). An additional factor which appears to play an important role with regard to transplantation immunity are exosomes, which are membrane-derived small vesicles released by various cells. However, the regulation of CD80+ DCs derived exosomes on CD8+ T cells in response to LT remains unclear. MethodsTen LT patients and two donors were included in this study. Multiple immunofluorescencewas performed to identify infiltratedCD8+ Tcells and DCs in human liver samples. The expression of NLRP3 and Ki-67 were measured usingimmunohistochemistry and immunofluorescence staining.Changes in CD80+ DCs and CD8+ T cells within the liver and blood of a mouse model of LT were detected with flow cytometry. After coculture with CD80+ DCs derived exosomes, the proliferation, adhesion, and transmigration ofCD8+ T cells were determined with the use of CCK-8, Adhesion and Transmigration assay in vitro.CD8+ T cells related cytokines were measured using Western blot, qRT-PCR and ELISA. ResultsIn human liver samples, there was an increase in intrahepatic CD8+ T cell infiltration in the acute LT rejection group, an effect which was accompanied by high expressions of NLRP3 and Ki-67 index and a decrease in DCs. Similarly, lower levels of CD80+ DCs were observed with acute rejection in an LT mouse model, along with increased numbers of CD8+ T cells in the liver and blood. In vitro, CD80+ DCs derived exosomes modulated the secretion of CD8+ T cells from cytokines by down-regulating NLRP3 expression, combined with a synchronous inhibition in the adhesion, invasion, and proliferation of CD8+ T cells. ConclusionCD80+ DCs derived exosomes negatively regulate CD8+ T cells via inhibition of NLRP3 expression, a series of events which are essential to attenuate acute LT rejection. These results reveal a new role for CD80+ DCs exosomes as related to tolerance induction in LT.

A network-based approach to identify expression modules underlying rejection in pediatric liver transplantation

SummarySelecting the right immunosuppressant to ensure rejection-free outcomes poses unique challenges in pediatric liver transplant (LT) recipients. A molecular predictor can comprehensively address these challenges. Currently, there are no well-validated blood-based biomarkers for pediatric LT recipients before or after LT. Here, we discover and validate separate pre- and post-LT transcriptomic signatures of rejection. Using an integrative machine learning approach, we combine transcriptomics data with the reference high-quality human protein interactome to identify network module signatures, which underlie rejection. Unlike gene signatures, our approach is inherently multivariate and more robust to replication and captures the structure of the underlying network, encapsulating additive effects. We also identify, in an individual-specific manner, signatures that can be targeted by current anti-rejection drugs and other drugs that can be repurposed. Our approach can enable personalized adjustment of drug regimens for the dominant targetable pathways before and after LT in children.

The Effect of Microcirculation Disturbance of Peribiliary Vascular Plexus on Hepatic Bile Duct Epithelial Cells in Rats Undergoing Liver Transplantation and Postoperative Rejection Reduction by Nanocarrier Mediation.

This study was to investigate the effect of microcirculation disturbance of PVP on HBD epithelial cells in rats undergoing liver transplantation and to explore the postoperative rejection reduction by nanocarriers mediation. For this aim, adult male rats weighing 210-250 g, were fed cleanly and were subjected to liver transplantation. 3 days after the surgery, the rats were randomly divided into three groups based on different intervention factors: group A (HAL), group B (HAMI combined with HAL), and group C (control). The three groups of rats were divided into three subgroups according to the duration of the University of Wisconsin (UW) solution (UW time) used to preserve the donor organs for transplantation, which were 2h, 8h, and 16h, respectively. In addition, the RNA sequence of rat class-II transactivator (CIITA) the rat was searched, and the target interference sequence was designed concerning the RNA. Results showed that the carrier nanoparticles were spherical without obvious oxygen vacancies, the distribution was relatively tight and concentrated, and the main particle size was 50-140 nm. As the mass ratio of HGPAE to DNA increased, the mobility speed of the nanocarrier/shRNA plasmid complex decreased due to the decrease in surface charge. When the mass ratio reached 90:1, the mobility of the complex was completely blocked, suggesting that the DNA was completely compounded. The counts of PCNA, CK-19, F-VIII-Ag, VEGFA, VEGFB, and VEGFC in the 3 groups all showed a downward trend with the increase of UW time; the count in group B was lower than that of groups A and C. In the PCNA count statistics, there was no obvious difference between group A and group B at UW8h, but there were differences in contrast to group C (p<0.05). It was concluded that the blood supply of the microcirculation of the PVP was extremely important for the transplanted liver tissue. When the blood vessels around the HBD of the rat were completely ischemic, the HBD epithelial cells became the most important target of damage, and the proliferation and changes of the HBD epithelial cells can be directly observed. In addition, the nanocarrier-mediated genes were applied to discuss postoperative rejection. The expression of class-II MHC-II gene in nanocarrier CIITA-shRNA was inhibited, which interfered with the recipient's immune recognition of the graft, thereby reducing the intensity of the rejection reaction and relieving the rejection reaction.

Adaptation of Imaging Mass Cytometry to Explore the Single Cell Alloimmune Landscape of Liver Transplant Rejection.

Rejection continues to be an important cause of graft loss in solid organ transplantation, but deep exploration of intragraft alloimmunity has been limited by the scarcity of clinical biopsy specimens. Emerging single cell immunoprofiling technologies have shown promise in discerning mechanisms of autoimmunity and cancer immunobiology. Within these applications, Imaging Mass Cytometry (IMC) has been shown to enable highly multiplexed, single cell analysis of immune phenotypes within fixed tissue specimens. In this study, an IMC panel of 10 validated markers was developed to explore the feasibility of IMC in characterizing the immune landscape of chronic rejection (CR) in clinical tissue samples obtained from liver transplant recipients. IMC staining was highly specific and comparable to traditional immunohistochemistry. A single cell segmentation analysis pipeline was developed that enabled detailed visualization and quantification of 109,245 discrete cells, including 30,646 immune cells. Dimensionality reduction identified 11 unique immune subpopulations in CR specimens. Most immune subpopulations were increased and spatially related in CR, including two populations of CD45+/CD3+/CD8+ cytotoxic T-cells and a discrete CD68+ macrophage population, which were not observed in liver with no rejection (NR). Modeling via principal component analysis and logistic regression revealed that single cell data can be utilized to construct statistical models with high consistency (Wilcoxon Rank Sum test, p=0.000036). This study highlights the power of IMC to investigate the alloimmune microenvironment at a single cell resolution during clinical rejection episodes. Further validation of IMC has the potential to detect new biomarkers, identify therapeutic targets, and generate patient-specific predictive models of clinical outcomes in solid organ transplantation.

Bone marrow mesenchymal stem cells modified with heme oxygenase-1 alleviate rejection of donation after circulatory death liver transplantation by inhibiting dendritic cell maturation in rats

Immature dendritic cells induce immune tolerance and mature dendritic cells induce acute rejection. We infused bone marrow mesenchymal stem cells (BMMSCs) expressing heme oxygenase 1 (HO-1) (HO-1/BMMSCs) into donation after circulatory death (DCD) livers using normothermic machine perfusion (NMP), and then performed transplantation, with the aim of determining the effects of HO 1/BMMSCs on liver DC maturation and graft rejection. A rat model of acute liver transplantation rejection was established from Lewis to BN rats, in which six experimental groups were set up: Sham operation, static cold storage, NMP, BMMSCs + NMP, HO-1/BMMSCs + NMP (HBP), and NMP + FK506 gavage. Flow cytometry was performed to detect the maturation of DCs and the activation of CD4+ T cells in the liver. In vitro, HO-1/BMMSCs were cocultured with liver DCs, and then the phenotype and ability to stimulate lymphocyte proliferation of DCs were measured. MAPK inhibitors were added to observe the effect of MAPK signaling on DC maturation. The resultsindicatedthatHO-1/BMMSCs could stably colonize the transplanted liver. In the HBP group, rejection was reduced, the maturation of DCs was inhibited, and the infiltration and activation of CD4+ T cells were reduced. In vitro, DCs cocultured with HO-1/BMMSCs showed an immature phenotype and inhibited T cell proliferation. HO-1/BMMSCs inhibited the maturation of DCs by blocking the phosphorylation of p38 and ERK1/2. This study suggested that infusion of HO-1/BMMSCs into DCD livers could reduce acute rejection significantly by inhibiting DC maturation. DC maturation regulation by HO-1/BMMSCs involves ERK1/2/MAPK and p38/MAPK signaling.

Effect of HO-1-modified BMMSCs on immune function in liver transplantation

We examined whether haem oxygenase-1 (HO-1) could enhance the immunosuppressive effects of bone marrow mesenchymal stem cells (BMMSCs) on the rejection of transplanted liver allografts in rats. The animals were divided into three groups: the normal saline (NS) group, BMMSC group and HO-1/BMMSCs group. In vitro, the extraction, culture and HO-1 transfection of BMMSCs were performed. Mixed lymphocyte response (MLR) analysis of HO-1/BMMSCs efficacy was performed. The rejection model of orthotopic liver transplantation in rats was established when BMMSCs and HO-1/BMMSCs were transfused via the portal vein. To reduce research bias, we established an isogenic Liver transplantation model of (LEW → LEW) and (BN → BN), which can achieve tolerance. Changes in histopathology and liver function in the transplanted liver and changes in regulatory T cell (Tregs), natural killer (NK) cells and cytokines after transplantation were observed in the different groups. The severe acute rejection after liver transplantation on postoperative Day 10 was observed in the NS group. The BMMSC group showed strong protective effects against rejection within the first 10 days after transplantation, while HO-1/BMMSCs showed stronger effects on rejection than BMMSCs alone. In addition, the activity of natural killer (NK) cells decreased significantly, the levels of regulatory T cells (Tregs), interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) increased significantly and the levels of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-23 (IL-23), tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) decreased significantly in the HO-1/BMMSC group compared with the BMMSC group. HO-1/BMMSCs showed better immunosuppressive effects after liver transplantation than the other treatments. Our findings reveal that HO-1 can enhance the effects of BMMSCs on inhibiting acute rejection in orthotopic liver transplantation in rats.

Biomarkers of rejection in liver transplantation.

Liver transplantation is a lifesaving therapy for thousands of individuals with end-stage liver disease across the world. Allograft rejection, which is traditionally detected through an invasive graft biopsy, is a major complication for liver transplant recipients in the postoperative period. Biomarkers represent a relatively newer and safer means of detecting and predicting transplant rejection when compared with the current standard of care: liver biopsy. This review serves to compile recent progress in the field of biomarker discovery in liver allograft rejection. Several promising biomarkers exist in the field of liver transplant rejection. Recent developments include blood genomic assays measuring miRNA, mRNA and donor-derived cell-free DNA. Additionally, serum levels of cytokines, proteoforms, donor-specific antibodies and immunophenotyping have shown promising results in predicting rejection pre and/or posttransplant. Biomarkers represent a novel method of predicting the risk of developing allograft rejection. The findings discussed in the studies outlined in this review are promising in the potential to improve patient management, reduce complications from over- or under-immunosuppression, and ultimately enhance outcomes.

Steroid-Resistant Rejection in Liver Transplant: A Single-Center Study for Risk Factor and Second-Line Treatment

Steroid-resistant rejection (SRR) in liver transplant occurs in about 10% of T cell-mediated rejection; prognosis of SRR is known to be worse than steroid-sensitive rejection (SSR). Only a few studies describe treatment methods or features for SRR, and there is no clear consensus yet. Therefore, the purpose of this study is to describe the difference between SSR and SRR and to compare the effect of the SRR treatment method performed our institution. This study is a 10-year, retrospective cohort study at Seoul St Mary's Hospital; clinical data were collected from January 2008 to December 2017. Of 663 cases, 154 patients (23.3%) underwent steroid pulse therapy for rejection; we excluded 30 patients who did not undergo liver biopsy. A total of 124 patients (18.7%) with biopsy-proven rejection were analyzed for this study. Child-Turcotte-Pugh score, cold ischemia time, and cytomegalovirus (CMV) infection showed a statistically significant difference in 2 groups. Multivariate analysis was performed on risk factors of SRR at first rejection. CMV infection and total bilirubin at first rejection and numbers of rejection were significant results. Both overall survival and allograft survival rate of SSR are higher than SRR (P < .001). Of second-line treatment patients, 13 patients (54.2%) recovered, and 11 patients (45.8%) failed to recover. Survival was the highest in patients using antithymocyte globulin and in patients with liver retransplant. When the first rejection in liver transplant occurs, patients with high bilirubin level ​​and previous CMV infections are more likely to have SRR, so if they do not respond to steroid pulse therapy for the first time, either using antithymocyte globulin or liver retransplant preparation should be considered.

Metronomic Capecitabine Inhibits Liver Transplant Rejection in Rats by Triggering Recipients’ T Cell Ferroptosis

Metronomic Capecitabine Inhibits Liver Transplant Rejection in Rats by Triggering Recipients’ T Cell Ferroptosis

Current state of clinical trials regarding liver transplant rejection

BackgroundLiver transplant (LT) is the second most common transplant intervention. The rate of acute cellular rejection (ACR) is 15–25% after LT, while being higher in chronic rejection (CR). Clinical trials had a major role in getting more potent and selective immunosuppressive medications. Our study plays an important role by evaluating and tracking clinical trials related to liver transplant rejection, focusing on interventional therapeutic trials. MethodsOn October 28, we searched Clinicaltrials.gov for interventional clinical trials related to liver transplant rejection. A total of 27 clinical trials included in this study. Characteristics on each trial were collected, and availability of linked publications was searched using Medline/PubMed and Embase/Scopus. Content of publications was reviewed and main findings were summarized. ResultsMajority of trials were completed (15 out of 27). Eleven trials had between 11 and 50 participants, and 10 had above 100. The study duration was between 1 and 4 years for the majority of trials (16 trials), with an average of 3.77 years. Most of the trials were done in Europe/UK/Russia (n = 12). The results were provided in 9 trials but published in 4, showing the possible tolerogenic efficacy of MSC in liver transplantation, increased success of immunosuppression (IS) withdrawal after sirolimus addition, efficacy of Alemtuzumab, normal graft function and stability within 1 year of immunosuppression withdrawal. ConclusionThis study revealed a low number of trials, lack of variety in location and low publishing rates. The focus of trials was mainly towards side effects and safety of immunosuppressants, and their withdrawal. These trials reached results that must be built on to reach definitive guidelines and treatment strategies. This highlights the need for better management of human and financial resources, in order to reach new and more effective therapeutic strategies, leading to the decrease in rate of LTR.

Determining the relevance of HLA/KIR matching/mismatching on kidney and liver transplantation rejection: A meta-analysis

Abstract. Batuan B, Cajayon CJ, Castro BA, Austria ML, Co DN, Ebreo SK, Clemente B, Tiongco RE. 2021. Determining the relevance of HLA/KIR matching/mismatching on kidney and liver transplantation rejection: A meta-analysis. Nusantara Bioscience 13: 211-218. The kidney and liver are solid organs commonly transplanted nowadays. However, there are cases wherein graft rejection occurs due to foreign Human Leukocyte Antigen (HLA) proteins. Furthermore, the function of Natural Killer (NK) cells and their receptors in solid organ transplantation is not yet fully elucidated. This study aims to determine the relevance of matching HLA/Killer cell Immunoglobulin-like Receptors (KIR) with kidney and liver transplantation outcomes. Articles were screened according to the inclusion and exclusion criteria provided, which garnered eight definitive studies. Next, data were tabulated using a standardized extraction form. A meta-analysis was conducted to formulate conclusions regarding significance of HLA/KIR matching and mismatching in kidney and liver transplantations. Fixed- and random-effects models were utilized to compute and establish 95% CI and pooled ORs wherein a p-value of less than 0.05 is considered significant. A combination of Chi-square based Q test and I2 statistics were used to identify heterogeneity, which was resolved with a funnel plot. In this meta-analysis, only the HLA-Bw4/KIR3DL1 combination was found significant to lower the risk of allograft rejection (OR=0.73; PA=0.009; PH=0.42). Other combinations which include HLA-C1 and KIR2DL2/3, HLA-C1 and KIR2DS2/3, HLA-C2 and KIR2DL1/DS2, and HLA-Bw4/KIR3DS1 were found to be insignificant; hence, these do not influence the allograft rejections. In conclusion, the role of HLA/KIR combinations on solid organ transplantation rejection is only significant in HLA-Bw4/KIR3DL1 interaction which is correlated with decreased odds of allograft rejection. Factors including KIR allele variations, insufficient data and journals related to the topic, and unestablished association of HLA/KIR in other organ transplantations affected the results of this meta-analysis; thus, these are recommended to be considered in future studies.

HO-1/BMMSC perfusion using a normothermic machine perfusion system reduces the acute rejection of DCD liver transplantation by regulating NKT cell co-inhibitory receptors in rats

BackgroundLiver transplantation (LT) is required in many end-stage liver diseases. Donation after cardiac death (DCD) livers are often used, and treatment of acute rejection (ACR) requires the use of immunosuppressive drugs that are associated with complications. Bone marrow mesenchymal stem cells (BMMSCs) are used in treatment following LT; however, they have limitations, including low colonization in the liver. An optimized BMMSC application method is required to suppress ACR.MethodsBMMSCs were isolated and modified with the heme oxygenase 1 (HO-1) gene. HO-1/BMMSCs were perfused into donor liver in vitro using a normothermic machine perfusion (NMP) system, followed by LT into rats. The severity of ACR was evaluated based on liver histopathology. Gene chip technology was used to detect differential gene expression, and flow cytometry to analyze changes in natural killer (NK) T cells.ResultsNMP induced BMMSCs to colonize the donor liver during in vitro preservation. The survival of HO-1/BMMSCs in liver grafts was significantly longer than that of unmodified BMMSCs. When the donor liver contained HO-1/BMMSCs, the local immunosuppressive effect was improved and prolonged, ACR was controlled, and survival time was significantly prolonged. The application of HO-1/BMMSCs reduced the number of NKT cells in liver grafts, increased the expression of NKT cell co-inhibitory receptors, and reduced NKT cell expression of interferon-γ.ConclusionsNK cell and CD8+ T cell activation was inhibited by application of HO-1/BMMSCs, which reduced ACR of transplanted liver. This approach could be developed to enhance the success rate of LT.

406.6: Pancreatic Graft Ultrasound Elastography: A Novel Non-invasive Technique in Rejection Assessment

Introduction: Rejection is the second cause of pancreatic graft loss after technical complications. Conventional imaging techniques lack sensitivity and specificity to assess rejection. Elastography by Acoustic Radiation Force Impulse (ARFI) quantification is a non-invasive ultrasonographic technique that allows quantification of tissue elasticity. It has been proposed as a complementary tool to detect rejection in liver and kidney transplantation. Unfortunately, there is no data on pancreas transplantation. Methods: Prospective study including all pancreas transplantations in our center from October 2016 to January 2020. All allografts were evaluated by ARFI(m/s) at 1 week after surgery. Thereafter, an ARFI evaluation and a protocolized biopsy were performed at 3 weeks and 12 months post-transplantation, also whenever a graft dysfunction was suspected and 3 weeks after a proven rejection. Allografts with postoperative surgical complications were excluded from the analysis. Grafts were classified according to the biopsy result into two groups (rejection/no rejection). Those cases without biopsy or with an inconclusive biopsy result were classified according to the clinical approach. ARFI values were analyzed in each group and compared between them. Results: During this period, 124 ARFI evaluations and 78 biopsies were performed in 54 patients. Three patients were excluded because of postoperative complications (5 evaluations). A high dispersion in ARFI values was recorded in the first three months in both groups: non-rejection group (n=88, 1.52±0.68 m/s) and rejection group (n=31, 1.55±0.46 m/s), which was attributed to the influence of postoperative factors and therefore these ARFI values were excluded from the analysis. After the first 3 months, the median ARFI values in the non-rejection group decreased to 0.98±0.32 m/s (n=55), which is similar to values reported in the native pancreas, whereas in the rejection group they reached a value of 1.45±0.31 m/s (n=16). This difference was found out to be statistically significant (p-value 0.0001). A cut-off value of 1.24 cm/s demonstrated a sensitivity and a specificity of 0.94 and 0.73 respectively (AUC 0.83) for the diagnosis of rejection in grafts older than 3 months.Conclusion: Elastography of the pancreatic graft shows a high dispersion of the values during the first postoperative 3 months probably due to postsurgical factors, making them less reliable. After this period, ARFI may be a useful non-invasive complementary tool to detect pancreatic graft rejection, selecting patients that may benefit from an early biopsy or an early treatment.

Multiplex Immunofluorescence for Detection of Spatial Distributions of Infiltrating T Cells Within Different Regions of Hepatic Lobules During Liver Transplantation Rejection.

It remains unclear as to whether there are differences that exist in the types and functional status of immune cells within different areas of the liver lobules after rejection of liver transplantation. The composition of infiltrating T cells in liver allografts during liver transplantation rejection is indistinct and difficult to visualize within the same biopsy slide. In an attempt to rectify this problem, we applied multiplex immunofluorescent assays to assess the spatial distribution of various types of infiltrating T cells in different areas of the liver lobules after liver transplantation. In identical areas of the hepatic lobules, the percentage of CD4+ T, CD8+ T, and regulatory T (Treg) cells in the rejection group was greater than that observed in the non-rejection and normal groups. Within all three groups, the percentage of CD4+ T, CD8+ T, and Treg cells from the periportal to perivenous zones initially increased and then decreased. In the rejection group, the percentage of CD8+ T cells gradually increased from the periportal to perivenous zones, with maximal levels in the perivenous as compared with that in the transitional and periportal zones. In conclusion, levels of CD8+ T cells within different regions of liver lobules are closely related to levels of rejection after liver transplantation. Liver transplantation rejection may be linked with increases in CD8+ T cells within the perivenous zone. Although the regional percent of increase in CD4+ T cells may not reflect level of the rejection, the overall numbers of both of CD4+ and CD8+ T cells within different regions were closely related to rejection levels.

Donor HLA Class 1 Evolutionary Divergence Is a Major Predictor of Liver Allograft Rejection : A Retrospective Cohort Study.

The HLA evolutionary divergence (HED), a continuous metric quantifying the peptidic differences between 2 homologous HLA alleles, reflects the breadth of the immunopeptidome presented to T lymphocytes. To assess the potential effect of donor or recipient HED on liver transplant rejection. Retrospective cohort study. Liver transplant units. 1154 adults and 113 children who had a liver transplant between 2004 and 2018. Liver biopsies were done 1, 2, 5, and 10 years after the transplant and in case of liver dysfunction. Donor-specific anti-HLA antibodies (DSAs) were measured in children at the time of biopsy. The HED was calculated using the physicochemical Grantham distance for class I (HLA-A or HLA-B) and class II (HLA-DRB1 or HLA-DQB1) alleles. The influence of HED on the incidence of liver lesions was analyzed through the inverse probability weighting approach based on covariate balancing, generalized propensity scores. In adults, class I HED of the donor was associated with acute rejection (hazard ratio [HR], 1.09 [95% CI, 1.03 to 1.16]), chronic rejection (HR, 1.20 [CI, 1.10 to 1.31]), and ductopenia of 50% or more (HR, 1.33 [CI, 1.09 to 1.62]) but not with other histologic lesions. In children, class I HED of the donor was also associated with acute rejection (HR, 1.16 [CI, 1.03 to 1.30]) independent of the presence of DSAs. There was no effect of either donor class II HED or recipient class I or class II HED on the incidence of liver lesions in adults and children. The DSAs were measured only in children. Class I HED of the donor predicts acute or chronic rejection of liver transplant. This novel and accessible prognostic marker could orientate donor selection and guide immunosuppression. Institut National de la Santé et de la Recherche Médicale.

S2680 Delayed T-cell Mediated Liver Transplant Rejection

S2680 Delayed T-cell Mediated Liver Transplant Rejection

Immunological Determinants of Liver Transplant Outcomes Uncovered by the Rat Model.

For many individuals with end-stage liver disease, the only treatment option is liver transplantation. However, liver transplant rejection is observed in 24%–80% of transplant patients and lifelong drug regimens that follow the transplant procedure lead to serious side effects. Furthermore, the pool of donor livers available for transplantation is far less than the demand. Well-characterized and physiologically relevant models of liver transplantation are crucial to a deeper understanding of the cellular processes governing the outcomes of liver transplantation and serve as a platform for testing new therapeutic strategies to enhance graft acceptance. Such a model has been found in the rat transplant model, which has an advantageous size for surgical procedures, similar postoperative immunological progression, and high genome match to the human liver. From rat liver transplant studies published in the last 5 years, it is clear that the rat model serves as a strong platform to elucidate transplant immunological mechanisms. Using the model, we have begun to uncover potential players and possible therapeutic targets to restore liver tolerance and preserve host immunocompetence. Here, we present an overview of recent literature for rat liver transplant models, with an aim to highlight the value of the models and to provide future perspectives on how these models could be further characterized to enhance the overall value of rat models to the field of liver transplantation.

Clinicopathologic Characteristics of Late Acute Antibody-mediated Rejection in Pediatric Liver Transplantation.

An early and accurate diagnosis of liver antibody-mediated rejection (AMR) followed by timely intervention is important for clinical management but remains challenging. The aim of this study was to assess the clinicopathologic characteristics and outcomes of late acute AMR in pediatric liver transplantation recipients. We performed a retrospective review of 739 ABO-identical/compatible allograft liver biopsies from 199 pediatric transplantation recipients. Based on Banff 2016 AMR criteria, 3 recipients fulfilled the criteria for definite for late acute AMR, 2 met the criteria for suspicious for AMR, and 2 were indeterminate for AMR. We further assessed the clinicopathologic characteristics of these 7 patients. All 7 patients had at least 1 biopsy with a histopathologic pattern compatible with acute AMR. Additionally, we observed accompanied moderately to markedly dilated portal/central veins and endothelialitis disproportionate to the degree of bile duct injury in all 7 patients; periportal/perivenular hepatocyte necrosis was seen in 6 of 7 patients; and arteritis was seen in 3 of 7 patients. In each case, microvascular C4d deposition was present in at least 1 biopsy. Posttransplant donor specific anti-HLA antibodies were detected in 5 patients. Two of 7 patients were retransplanted, and 2 died after developing refractory AMR. The remaining 5 patients were alive with stable graft function at a median follow-up of 4.1 years. Our data suggest that acute AMR in pediatric liver grafts is rare, can develop late, and may be associated with graft loss or patient death. The recurrent histopathologic findings of moderately to markedly dilated portal/central veins and endothelialitis disproportionate to the degree of bile duct injury are features that appear unique to pediatric acute AMR of liver grafts.