De novo donor-specific HLA antibodies decrease patient and graft survival in liver transplant recipients

High tacrolimus intra-patient variability is associated with graft rejection, and de novo donor-specific antibodies occurrence after liver transplantation

AIM

To investigate the role of tacrolimus intra-patient variability (IPV) in adult liver-transplant recipients.

METHODS

We retrospectively assessed tacrolimus variability in a cohort of liver-transplant recipients and analyzed its effect on the occurrence of graft rejection and de novo donor-specific antibodies (dnDSAs), as well as graft survival during the first 2 years posttransplantation. Between 02/08 and 06/2015, 116 patients that received tacrolimus plus mycophenolate mofetil (with or without steroids) were included.

RESULTS

Twenty-two patients (18.5%) experienced at least one acute-rejection episode (BPAR). Predictive factors for a BPAR were a tacrolimus IPV of > 35% [OR = 3.07 95%CI (1.14-8.24), P = 0.03] or > 40% [OR = 4.16 (1.38-12.50), P = 0.01), and a tacrolimus trough level of < 5 ng/mL [OR=3.68 (1.3-10.4), P =0.014]. Thirteen patients (11.2%) developed at least one dnDSA during the follow-up. Tacrolimus IPV [coded as a continuous variable: OR = 1.1, 95%CI (1.0-1.12), P = 0.006] of > 35% [OR = 4.83, 95%CI (1.39-16.72), P = 0.01] and > 40% [OR = 9.73, 95%CI (2.65-35.76), P = 0.001] were identified as predictors to detect dnDSAs. IPV did not impact on patient- or graft-survival rates during the follow-up.

CONCLUSION

Tacrolimus-IPV could be a useful tool to identify patients with a greater risk of graft rejection and of developing a de novo DSA after liver transplantation

Acute Graft Rejection and Formation of De Novo Donor-Specific Antibodies Triggered by Low Cyclosporine Levels and Interferon Therapy for Recurrent Hepatitis C Infection After Liver Transplantation: A Case Report

BACKGROUND

We report a case of acute rejection of a liver graft, together with the occurrence of de novo donor-specific antibodies (DSAs), in a 53-year-old Japanese man who had undergone deceased-donor liver transplantation.

METHODS

The graft rejection was triggered by low cyclosporine levels and pegylated interferon treatment for the recurrence of hepatitis C virus (HCV) infection 18 months after transplantation. Although the graft was ABO-compatible, pre-formed DSA B51 was detected; therefore, total plasma exchange was performed and intravenous rituximab (500 mg/body) was administered before transplantation.

RESULTS

DSA was absent 6 months after transplantation. HCV recurrence was treated with pegylated interferon-α-2a. Renal function deteriorated with this anti-HCV therapy, with serum cyclosporine levels decreasing to 50 ng/mL. A rapid virologic response was achieved, but liver function deteriorated after 3 months of anti-HCV therapy, with histologic evidence of acute cellular rejection and formation of de novo DSAs. Anti-thymocyte globulin was administered for 5 days, which led to immediate improvement in liver function. However, renal function declined, warranting hemodialysis. The patient recovered 2 months after acute rejection, although de novo DSAs persisted.

CONCLUSIONS

Careful immunologic monitoring may be required for patients receiving interferon therapy for HCV infection to maintain sufficient blood levels of immunosuppressive agents and to prevent acute liver graft rejection.

Effect of Early Immunosuppression Therapy on De Novo Anti-Human-Leukocyte-Antigen Antibody After Kidney Transplantation

The aim of the study was to investigate the effect of immunosuppression therapy early after kidney transplantation, particularly exposure of mycophenolic acid (MPA) and calcineurin inhibitor (CNI), on posttransplantation de novo HLA antibody production.

METHODS

A single-center retrospective cohort study was performed at the First Affiliated Hospital of Sun Yat-sen University, enrolling the kidney transplant or pancreas-kidney transplant recipients who had surgery between January 2010 and February 2016.

RESULTS

A total of 214 recipients were included in the study with a median follow-up period of 1.06 years. A total of 30 recipients (14.0%) were positive in HLA antibody detection posttransplant with a median follow-up period of 1.46 years. Ten recipients (4.7%) lost their allograft function during follow-up, and 6 of them (60%) developed de novo HLA antibody after graft failure. Multivariate analysis showed that acute rejection significantly increased the risk of de novo HLA antibody (hazard ratio [HR], 2.732). Intensified MPA dosing therapy reduced the risk by 59.8% (HR, 0.402); low-dose CNI therapy increased the risk by 33.3% (HR, 1.333), and the effect of extremely low-dose CNI therapy was even larger (HR, 2.242).

CONCLUSION

The risk of de novo HLA antibody can be decreased by reducing the risk of acute rejection. A tendency was seen in low-dose CNI therapy to increase the risk of de novo HLA antibody, but intensified MPA dosing therapy may provide an umbrella protection effect by reducing the risk. Prospective study was required to confirm the effects.

Successful living donor liver retransplantation for graft failure within 7 days due to acute de novo donor-specific anti-human leukocyte antigen antibody-mediated rejection

Growing evidence suggests a relationship between antibody-mediated rejection (AMR) and early graft failure due to a previously unknown etiology in liver transplantation (LTx). We herein report a 3-year-old boy who developed rapid graft failure due to de novo donor-specific antibody (DSA)-driven AMR a week after living donor LTx, requiring a second transplant on the 10th day after the first LTx. The pathology of the first graft showed massive necrosis in zone 3 along with positive C4d and inflammatory cell infiltrates in portal areas. The mean fluorescence intensity against human leukocyte antigen (HLA)-DR15, which was possessed by both the first and the second donor, peaked at 12 945 on the day before the second LTx. Antithymocyte globulin, plasma exchange along with i.v. immunoglobulin, rituximab, and the local infusion of prostaglandin E1, steroids, and Mesilate gabexate through a portal catheter were provided to save the second graft. To our knowledge, this is the first report to show a clear association between de novo DSA and acute AMR within 7 days of a LTx. Furthermore, we successfully rescued the recipient with a second graft despite possessing the same targeted HLA. The rapid decision to carry out retransplantation and specific strategies overcoming AMR were crucial to achieving success in this case of immunologically high-risk LTx.

The impact of repeated mismatches in kidney transplantations performed after nonrenal solid organ transplantation

The aim of this study was to determine whether kidney transplantations performed after previous nonrenal solid organ transplants are associated with worse graft survival when there are repeated HLA mismatches (RMM) with the previous donor(s). We performed a retrospective cohort study using data from the Scientific Registry of Transplant Recipients. Our cohort comprised 6624 kidney transplantations performed between January 1, 1990 and January 1, 2015. All patients had previously received 1 or more nonrenal solid organ transplants. RMM were observed in 35.3% of kidney transplantations and 3012 grafts were lost over a median follow-up of 5.4 years. In multivariate Cox regression analyses, we found no association between overall graft survival and either RMM in class 1 (hazard ratio [HR]: 0.97, 95% confidence interval [CI] 0.89-1.07) or class 2 (HR: 0.95, 95% CI 0.85-1.06). Results were similar for the associations between RMM, death-censored graft survival, and patient survival. Our results suggest that the presence of RMM with previous donor(s) does not have an important impact on allograft survival in kidney transplant recipients who have previously received a nonrenal solid organ transplant.

Tolerance after liver transplantation: Where are we?

Impeccable management of immunosuppression is required to ensure the best longterm outcomes for liver transplant recipients. This is particularly challenging for children who arguably need 8 decades of graft and patient survival. Too little risks chronic, often subclinical allo-immune injury while too much risks insidious and cumulative toxicities. Historically, immunosuppression minimization or withdrawal has been a strategy to optimize the longevity of liver transplant recipients. The literature is sprinkled with single-center reports of operationally tolerant patients - those with apparently normal liver function and liver tests. However, without biopsy evidence of immunological quiescence, confidence in the phenotypic assignment of tolerance is shaky. More recently, multicenter trials of immunosuppression withdrawal for highly selected, stable, longterm adult and pediatric liver recipients have shown tolerance rates, based on both biochemical and histological assessment, of 40% and 60%, respectively. Extended biochemical and histologic follow-up of children over 8 years, equivalent to 7+ years off of drug, suggests that operational tolerance is robust. Therefore, clearly, immunosuppression can be completely and safety withdrawn from highly-selected subsets of adults and children. However, these trials have also confirmed that clinically ideal recipients - those eligible for immunosuppression withdrawal trial - can harbor significant and worrisome inflammation and/or fibrosis. Although the etiology and prognosis of these findings remain unknown, it is reasonable to surmise that they may reflect an anti-donor immune response that is insufficiently controlled. To achieve the outcomes that we are seeking and that our patients are demanding, we desperately need noninvasive but accurate biomarkers that identify whether immunosuppression is neither too much nor too little but "just right." Until these are available, liver histology remains the gold standard to assess allograft health and guide immunosuppression management. Liver Transplantation 23 1601-1614 2017 AASLD.

HLA-DQ antibodies: are they real? Are they relevant? Why so many?

PURPOSE OF REVIEW

Recent reports on donor-specific antibodies documented an overwhelming frequency of antibodies to one specific locus - human leukocyte antigen DQ (HLA-DQ). This article provides a short summary of clinical observations, a historic perspective to account for the late recognition of the role of HLA-DQ antibodies as well as potential explanations.

RECENT FINDINGS

The basic understanding of the complexity of HLA-DQ molecules (antigens and antibodies) existed already 3-4 decades ago. However, only more recent advancements in molecular techniques as well as solid phase platforms, that allow for testing antibody specificities against individual HLA targets, provided state-of-the-art tools that are also amenable to mass applications. Thus, the significance of the polymorphic nature of both polypeptide chains of the DQ molecule, DQα and DQβ, is only now re-emerging.

SUMMARY

HLA-DQ antibodies are real, relevant, and abundant. In order to achieve a clinically useful understanding of this phenomenon, HLA-DQ antigens and antibodies should be viewed at the level of the physiologic structure, as it appears on the cell surface, namely, one unit composed as DQαβ. Preliminary data demonstrated that such an approach is likely to lead to more equitable calculation of calculated panel reactive antibody, improving the accuracy of virtual crossmatch prediction, and increasing the likelihood of finding a compatible donor for the very highly sensitized patients.

Antibody-mediated rejection: what is the clinical relevance?

PURPOSE OF REVIEW

The review outlines the diagnosis, clinical implications, and treatment strategies for acute and chronic antibody-mediated rejection (AMR) after orthotopic liver transplantation (OLT).

RECENT FINDINGS

A combination of clinical work-up, histopathology, C4d staining, and donor-specific antibody (DSA) should be used to diagnose AMR. The differential diagnosis for idiopathic fibrosis now includes chronic AMR. Characterization of pathogenic DSA continues to progress. De-novo and persistent DSA, particularly of the IgG3 subtype, are associated with inferior long-term outcomes.The liver allograft may confer long-term immunologic benefits to the kidney allograft after simultaneous liver-kidney transplant.The more widespread use of rituximab has improved outcomes in ABO-incompatible OLT.Although larger long-term studies of treatment options are needed, compliance with tacrolimus-based immunosuppression and transfusion minimization are agreed upon preventive strategies.

SUMMARY

AMR has evolved into an established pathology in OLT recipients. Acute AMR may lead to early graft loss whereas chronic AMR results in progressive fibrosis if unrecognized. DSAs, likely in the setting of predisposing environmental factors, appear to play a role in T cell-mediated rejection and long-term graft outcomes.

Tolerance in clinical liver transplantation

While advances in immunosuppressive therapy have lowered the rate of acute rejection following liver transplantation, the consequence has been an increase in morbidity and mortality related to the lifelong need for maintenance immunosuppression. These complications include an increased risk of malignancy, infection, metabolic disorders, and chronic kidney disease, as well as high health care costs associated with these therapies and the required drug monitoring. Given these issues, most clinicians attempt trial and error dose minimization with variable success rates, and there has been significant interest in full drug withdrawal in select patients through research protocols. These strategies would be more successful if immunomodulatory therapies early after transplantation could be developed and if immune activation biomarkers guiding drug tapering were available to personalize these approaches. This review will review the mechanisms of liver transplant tolerance and potential strategies to achieve immunosuppression withdrawal.

Chronic AMR in Liver Transplant: Validation of the 1-Year cAMR Score's Ability to Determine Long-term Outcome

BACKGROUND

A proposed chronic antibody-mediated rejection (AMR) score has recently predicted 50%10-year death-censored allograft loss in patients with donor-specific alloantibodies (DSA) mean florescence intensity (MFI) greater than 10 000 and requires confirmation in patients with lower MFI (1000-10 000).

METHODS

All patients who underwent liver transplantation from January 2000 to April 2009, had DSA (MFI ≥1000) in serum 10 to 14 months postliver transplantation, and had a protocolized liver biopsy were evaluated (n = 230). The previously proposed chronic AMR (cAMR) score was used to risk-stratify putative chronic AMR in DSA+ patients with MFI from 1000 to 10 000.

RESULTS

The MFI distribution of DSA+ recipients were as follows: 66% had MFI 1000 to 4999, 14% had MFI 5000 to 10 000, and 20% had MFI greater than 10 000. The cAMR score distribution on 1-year protocol liver biopsy found that 41% had a score less than 13; 27% a score of 13 to 27.5, and 32% a score greater than 27.5. MFI correlated with 1-year cAMR category (<13, 46% vs 21% and >27.5, 29% vs 42% when MFI was 1000-10 000 vs MFI >10 000; P = 0.047). In patients with a cAMR score less than 13, 10-year death-censored allograft survival was 96% to 100% regardless of MFI (P = NS). The risk of allograft loss increased in patients with a cAMR score greater than 13 (P = 0.004) in DSA+ patients with MFI 1000 to 10 000. DSA MFI greater than 10 000 versus MFI 1000 to 10 000 at 1 year was also more likely to persist at 5 years (95% vs 68%; P < 0.0001).

CONCLUSIONS

Validation of the previously proposed cAMR score in a separate cohort predicts death-censored long-term allograft failure in DSA+ patients regardless of MFI, and higher MFI at 1 year predicts DSA persistence at 5 years.

A Memory B Cell Crossmatch Assay for Quantification of Donor-Specific Memory B Cells in the Peripheral Blood of HLA-Immunized Individuals

Humoral responses against mismatched donor HLA are routinely measured as serum HLA antibodies, which are mainly produced by bone marrow-residing plasma cells. Individuals with a history of alloimmunization but lacking serum antibodies may harbor circulating dormant memory B cells, which may rapidly become plasma cells on antigen reencounter. Currently available methods to detect HLA-specific memory B cells are scarce and insufficient in quantifying the complete donor-specific memory B cell response due to their dependence on synthetic HLA molecules. We present a highly sensitive and specific tool for quantifying donor-specific memory B cells in peripheral blood of individuals using cell lysates covering the complete HLA class I and class II repertoire of an individual. Using this enzyme-linked immunospot (ELISpot) assay, we found a median frequency of 31 HLA class I and 89 HLA class II-specific memory B cells per million IgG-producing cells directed at paternal HLA in peripheral blood samples from women (n = 22) with a history of pregnancy, using cell lysates from spouses. The donor-specific memory B cell ELISpot can be used in HLA diagnostic laboratories as a cross-match assay to quantify donor-specific memory B cells in patients with a history of sensitizing events.

Impact of Antibodies That React With Liver Tissue and Donor-Specific Anti-HLA Antibodies in Pediatric Idiopathic Posttransplantation Hepatitis

Background

The cause of late graft dysfunction has not been elucidated. Although an antibody-mediated reaction is suspected as a potential mechanism, the target antigens have not been clarified.

Methods

To clarify the etiology of idiopathic posttransplantation hepatitis (IPTH), we simultaneously examined the presence of antibodies that react with liver tissue (ARLT) by means of indirect immunofluorescence staining, as well as the presence of donor-specific anti-human leukocyte antigen antibodies (HLA-DSA). A subanalysis of the IPTH group was also performed. Within the IPTH group, the correlation between ARLT titer and clinical data were analyzed.

Results

In the sera of patients with IPTH (30 patients), ARLT were found at a significantly higher frequency than in patients without IPTH (42 patients; P < 0.001). Moreover, the ARLT titer appeared to be correlated with the severity of hepatitis or hepatic injury. In contrast, the frequency of HLA-DSA was significantly lower in patients with IPTH than in patients without IPTH (P = 0.001).

Conclusion

Our findings indicate that ARLT, and not HLA-DSA, profoundly influence the etiology of IPTH.

The authors show that antibodies that react with liver tissue and not donor-specific anti-human leukocyte antigen antibodies, profoundly influence the etiology of idiopathic posttransplantation hepatitis in children providing a rationale for therapy.

Deleterious impact of C3d-binding donor-specific anti-HLA antibodies after pediatric liver transplantation

BACKGROUND

The prevalence and clinical impact of anti-HLA donor-specific antibodies (DSA) after liver transplantation (LT) have not been extensively studied, especially in pediatric population.

METHODS

The present cross-sectional study included 100 patients who underwent a first LT in childhood. Anti HLA immunization study was performed at a single time point during routine follow-up using Luminex® single antigen tests with classical anti-IgG conjugate and anti-C3d conjugate.

RESULTS

The main indication for LT was biliary atresia (52%) and median age at LT was 4.6years. The median time between LT and DSA assessment was 7.8years (range 1-21years). DSA was identified in twenty-four patients (24%) after LT, with a prevalence of 8%, 28%, 33%, 50%, respectively 0-5years, 5-10years, 10-15years and >15years after LT. DSA were mainly class II (23/24) with a mean MFI of 9.731±5.489 and 18 (79.3%) were C3d-binding DSA. Multivariate analysis disclosed that time elapsed since LT (p<0.01) and history of fulminant hepatitis (p=0.04) were significantly associated with a higher rate of DSA. Liver function tests (at time of DSA assessment) were not different according to the presence or not of DSA (or C3d-binding DSA). Regarding histology, the DSA group had a higher rate of chronic rejection, cirrhosis and centrilobular fibrosis or cirrhosis. In addition, patients with C3d-binding DSA and high MFI (>10,000) had a significant poorer long-term graft survival (p=0.03).

CONCLUSION

In our pediatric cohort of LT, prevalence of DSA was high and increased regularly with time. Presence of C3d positive-DSA with high MFI was associated with a higher rate of graft loss.

Impact of the Trough Level of Calcineurin Inhibitor on the Prevalence of Donor-Specific Human Leukocyte Antigen Antibodies During Long-Term Follow-Up After Pediatric Liver Transplantation: Antibody Strength and Complement-Binding Ability

Background

In pediatric patients, long-term immunosuppression after liver transplantation (LT) is typically minimal. However, posttransplant donor-specific HLA antibodies (DSAs) may be prevalent under these conditions. Here, we evaluated the effects of minimized calcineurin inhibitor (CNI) on DSA development to assess the validity of minimized/withdrawn immunosuppression.

Methods

We retrospectively examined 66 patients who underwent pediatric LT at our institution between July 1991 and October 2013. Patients were divided into 2 groups based on the CNI trough level. The cutoff trough levels were 3 and 30 ng/mL for tacrolimus and cyclosporine, respectively. Luminex single-antigen bead assays were performed, and the cutoff for a positive reaction was set at a mean fluorescence intensity (MFI) of at least 1000.

Results

The mean recipient ages at the time of LT were 29.1 and 77.2 months for the low and regular CNI groups, respectively (P = 0.0007). Univariate logistic regression analysis revealed that recipient age at LT younger than 3 years (P = 0.0099) and low CNI (P < 0.0001) were significantly associated with DSA development. In multivariate analysis, low CNI was an independent risk factor of DSA development (P = 0.0011). Of 15 high-MFI DSAs, 3 were anti-DR, and 12 were anti-DQ. Two of 3 anti-DR DSAs and 11 of 12 anti-DQ DSAs had complement-binding ability and high MFIs.

Conclusions

CNI minimization was an independent risk factor for posttransplant DSA during long-term follow-up after pediatric LT. Adjusting CNI to appropriate levels is a safe first step to prevent the immunological effects of DSA.

Antibody-mediated rejection across solid organ transplants: manifestations, mechanisms, and therapies

Solid organ transplantation is a curative therapy for hundreds of thousands of patients with end-stage organ failure. However, long-term outcomes have not improved, and nearly half of transplant recipients will lose their allografts by 10 years after transplant. One of the major challenges facing clinical transplantation is antibody-mediated rejection (AMR) caused by anti-donor HLA antibodies. AMR is highly associated with graft loss, but unfortunately there are few efficacious therapies to prevent and reverse AMR. This Review describes the clinical and histological manifestations of AMR, and discusses the immunopathological mechanisms contributing to antibody-mediated allograft injury as well as current and emerging therapies.

Antibody-Mediated Rejection After Liver Transplant

Antibody-mediated rejection (AMR) in liver transplants is a field in its infancy compared with its allograft cohorts of the kidney and lung. Acute AMR is diagnosed based on specific clinical and histopathologic criteria: serum donor specific antibodies, C4d staining, histopathologic findings on liver biopsy, and exclusion of other entities. In contrast, the histologic features of chronic AMR are not as specific and it is a more challenging diagnosis to make. Treatments of acute and chronic AMR include some combination of steroids, immune-modulating agents, intravenous immunoglobulin, plasmapheresis, and proteasome inhibitors.

Potential Roles for C1 Inhibitor in Transplantation

Complement is a major contributor to inflammation and graft injury. This system is especially important in ischemia-reperfusion injury/delayed graft function as well as in acute and chronic antibody-mediated rejection (AMR). The latter is increasingly recognized as a major cause of late graft loss, for which we have few effective therapies. C1 inhibitor (C1-INH) regulates several pathways which contribute to both acute and chronic graft injuries. However, C1-INH spares the alternative pathway and the membrane attack complex (C5–9) so innate antibacterial defenses remain intact. Plasma-derived C1-INH has been used to treat hereditary angioedema for more than 30 years with excellent safety. Studies with C1-INH in transplant recipients are limited, but have not revealed any unique toxicity or serious adverse events attributed to the protein. Extensive data from animal and ex vivo models suggest that C1-INH ameliorates ischemia-reperfusion injury. Initial clinical studies suggest this effect may allow transplantation of donor organs which are now discarded because the risk of primary graft dysfunction is considered too great. Although the incidence of severe early AMR is declining, accumulating evidence strongly suggests that complement is an important mediator of chronic AMR, a major cause of late graft loss. Thus, C1-INH may also be helpful in preserving function of established grafts. Early clinical studies in transplantation suggest significant beneficial effects of C1-INH with minimal toxicity. Recent results encourage continued investigation of this already-available therapeutic agent.

De Novo Donor-Specific Anti-Human Leukocyte Antigen Antibody Detection in Long-Term Adult Liver Transplantation

INTRODUCTION

Information about the consequences of de novo donor-specific anti-human leukocyte antigen (DSA) antibody development in the long term after adult liver transplantation (LT) is scarce. We conducted a cross-sectional study in LT patients with a follow-up of at least 6 years.

METHODS

A total of 28 adult LT patients were included, with a median follow-up of 77 months (range, 63 to 96) and without preformed anti- human leukocyte antigen (HLA) antibodies prior to LT. The anti-HLA identification was performed with LABScreen Single Antigen, whereas the ability to fix the complement was demonstrated with C1q test (One Lambda). In both assays, a value >3.500 mean fluorescence intensity (MFI) was considered positive. The anti-HLA antibody specificities were compared with donor HLA antigens to confirm them as DSA. Hepatic fibrosis was assessed by transient elastography.

RESULTS

In 5 patients (17.8%), de novo DSA were detected, all them against DQ locus. In all of these cases (100%) the complement fixation was confirmed by C1q binding. The grade of hepatic fibrosis in de novo DSA patients was significantly higher compared with No-DSA patients (13.2 ± 9.2 KPa vs 7.3 ± 3.7 KPa; P = .02). It is noteworthy that in both groups of patients the levels of liver function tests (LFT) at the time of the study were normal or near the normal range with no difference between patients with or without de novo DSA.

CONCLUSIONS

Our preliminary results are consistent with those previously demonstrated in pediatric LT, where de novo DSA production and humoral response could contribute to the liver fibrosis observed in the long term after LT in pediatric patients with normal or near-normal LFT.

mTOR Inhibition Suppresses Posttransplant Alloantibody Production Through Direct Inhibition of Alloprimed B Cells and Sparing of CD8+ Antibody-Suppressing T cells

BACKGROUND

De novo alloantibodies (donor-specific antibody) contribute to antibody-mediated rejection and poor long-term graft survival. Because the development of donor-specific antibody is associated with early graft loss of cell transplants and reduced long-term survival of solid organ transplants, we hypothesized that conventional immunosuppressives, calcineurin inhibitors (CNi), and mammalian target of rapamycin inhibitors (mTORi), may not be as effective for suppression of humoral alloimmunity as for cell-mediated immunity.

METHODS

Wild-type or CD8-depleted mice were transplanted with allogeneic hepatocytes. Recipients were treated with mTORi and/or CNi and serially monitored for alloantibody and graft survival. The direct effect of mTORi and CNi on alloprimed B cell function was investigated in Rag1 mice adoptively transferred with alloprimed IgG1 B cells. The efficacy of mTORi and/or CNi to suppress CD8-mediated cytotoxicity of IgG1 B cells was evaluated in in vitro and in vivo cytotoxicity assays.

RESULTS

Mammalian target of rapamycin inhibitors, but not CNi, reduced alloantibody production in transplant recipients, directly suppressed alloantibody production by alloprimed IgG1 B cells and delayed graft rejection in both low and high alloantibody producers. Combination treatment with mTORi and CNi resulted in loss of the inhibitory effect observed for mTORi monotherapy in part due to CNi suppression of CD8 T cells which downregulate alloantibody production (CD8 TAb-supp cells).

CONCLUSIONS

Our data support that mTORi is a potent inhibitor of humoral immunity through suppression of alloprimed B cells and preservation of CD8 TAb-supp cells. In contrast, alloantibody is readily detected in CNi-treated recipients because CNi does not suppress alloprimed B cells and interferes with downregulatory CD8 TAb-supp cells.

Practical Recommendations for Long-term Management of Modifiable Risks in Kidney and Liver Transplant Recipients: A Guidance Report and Clinical Checklist by the Consensus on Managing Modifiable Risk in Transplantation (COMMIT) Group

Short-term patient and graft outcomes continue to improve after kidney and liver transplantation, with 1-year survival rates over 80%; however, improving longer-term outcomes remains a challenge. Improving the function of grafts and health of recipients would not only enhance quality and length of life, but would also reduce the need for retransplantation, and thus increase the number of organs available for transplant. The clinical transplant community needs to identify and manage those patient modifiable factors, to decrease the risk of graft failure, and improve longer-term outcomes.COMMIT was formed in 2015 and is composed of 20 leading kidney and liver transplant specialists from 9 countries across Europe. The group's remit is to provide expert guidance for the long-term management of kidney and liver transplant patients, with the aim of improving outcomes by minimizing modifiable risks associated with poor graft and patient survival posttransplant.The objective of this supplement is to provide specific, practical recommendations, through the discussion of current evidence and best practice, for the management of modifiable risks in those kidney and liver transplant patients who have survived the first postoperative year. In addition, the provision of a checklist increases the clinical utility and accessibility of these recommendations, by offering a systematic and efficient way to implement screening and monitoring of modifiable risks in the clinical setting.

Histological long-term outcomes from acute antibody-mediated rejection following ABO-compatible liver transplantation

BACKGROUND AND AIM

Acute antibody-mediated rejection (aAMR) is an unusual complication after orthotopic ABO-compatible liver transplantation. To date, the clinical and histological long-term outcomes after aAMR are not well known.

METHOD

Herein, we describe nine cases of aAMR that occurred in our liver-transplant center between 2008 and 2016, with an initial and reevaluation liver biopsy available for reexamination.

RESULTS

Two patients presented with aAMR at 10.5 (10, 11) days post-transplantation, caused by preformed donor-specific antibodies. Seven other recipients developed de novo donor-specific antibodies and aAMR at 11.2 (3-24) months post-transplantation. Eight of the nine patients received a B-cell targeting agent (rituximab, with or without plasma exchange), associated with polyclonal antibodies (three patients) or intravenous immunoglobulins (three patients). At the last follow up (i.e. 21 [4-90] months post-aAMR), seven patients were alive, including two patients with normal liver tests. Grafts' survival was 66%. A liver biopsy performed at 11.5 (5-48.5) months after the first biopsy showed no significant improvement in aAMR score (from 2 ± 1.3 to 1.6 ± 1.5, P = 0.6), a significant improvement in chronic AMR score (from 37 ± 9 to 25 ± 8, P = 0.003) and an increase in the Metavir score (1.2 ± 0.6 to 2.1 ± 0.9, P = 0.03).

CONCLUSION

In this study, a B-cell-depleting agent seemed to improve the prognosis of aAMR in selected cases, but several patients kept active lesions antibody-mediated rejection.

Five-year histological and serological follow-up of operationally tolerant pediatric liver transplant recipients enrolled in WISP-R

Pediatric liver transplant recipients arguably have the most to gain and the most to lose from discontinuing immunosuppression (IS). Whereas IS undoubtedly exerts a cumulative toll, there is concern that insufficient or no IS may contribute to allograft deterioration. Twelve pediatric recipients of parental living donor liver grafts, identified as operationally tolerant through complete IS withdrawal (WISP-R; NCT00320606), were followed for a total of 5 years (1 year of IS withdrawal and 4 years off IS) with serial liver tests and autoantibody and alloantibody assessments. Liver biopsies were performed 2 and 4 years off IS, and, at these time points, immunoglobulin G (IgG) subclass and C1q binding activity for donor-specific antibodies (DSAs) were determined. There were no cases of chronic rejection, graft loss, or death. Allografts did not exhibit progressive increase in inflammation or fibrosis. Smooth-muscle actin expression by stellate cells and CD34 expression by liver sinusoidal endothelial cells remained stable, consistent with the absence of progressive graft injury. Three subjects never exhibited DSA. However, 3 subjects showed intermittent de novo class I DSA, 4 subjects showed persistent de novo class II DSA, and 5 subjects showed persistent preexisting class II DSA. Class II DSA was predominantly against donor DQ antigens, often of high mean fluorescence intensity, rarely of the IgG3 subclass, and often capable of binding C1q.

CONCLUSION

Operationally tolerant pediatric liver transplant recipients maintain generally stable allograft histology in spite of apparently active humoral allo-immune responses. The absence of increased inflammation or progressive fibrosis suggests that a subset of liver allografts seem resistant to the chronic injury that is characteristic of antibody-mediated damage. (Hepatology 2017;65:647-660).

B Cell Immunity in Solid Organ Transplantation

The contribution of B cells to alloimmune responses is gradually being understood in more detail. We now know that B cells can perpetuate alloimmune responses in multiple ways: (i) differentiation into antibody-producing plasma cells; (ii) sustaining long-term humoral immune memory; (iii) serving as antigen-presenting cells; (iv) organizing the formation of tertiary lymphoid organs; and (v) secreting pro- as well as anti-inflammatory cytokines. The cross-talk between B cells and T cells in the course of immune responses forms the basis of these diverse functions. In the setting of organ transplantation, focus has gradually shifted from T cells to B cells, with an increased notion that B cells are more than mere precursors of antibody-producing plasma cells. In this review, we discuss the various roles of B cells in the generation of alloimmune responses beyond antibody production, as well as possibilities to specifically interfere with B cell activation.

Intestine Transplantation Across a Positive Crossmatch With Preformed Donor-Specific Antibodies

BACKGROUND

We describe our experience using a modified protocol for immunosuppression for intestine transplantation across a positive crossmatch. Patients who underwent transplantation in 2013 were evaluated over a 12-month period for rejection and infectious events with comparison to procedure-matched controls on our standard protocol of immunosuppression.

PATIENTS AND METHODS

We used a modified protocol for intestine and multivisceral transplantation for patients with a positive flow crossmatch. In addition to our standard protocol, patients with positive crossmatch were given rituximab and intravenous immunoglobulin (IVIg) preoperatively. DSA was sent for clinical evaluation at monthly intervals. Patients were screened for rejection by endoscopic evaluation.

RESULTS

Four patients underwent transplantation within a single year across a positive crossmatch. Two received isolated intestine transplants and 2 had multivisceral transplantation (MVT). During the 12-month follow-up, 1 patients had an episode of severe acute cellular rejection, which was managed with increased immunosuppression. None of the patients had episodes of cytomegalovirus infection. One patient developed major infection and 3 patients developed minor bacterial infections. Among procedure-matched controls with negative final crossmatch on standard management (no preoperative rituximab or IVIg), 2 developed mild acute cellular rejection and 2 developed minor infections. One developed cytomegalovirus viremia with invasion to the colonic mucosa.

CONCLUSIONS

We report our protocol for immunosuppression for IT and MVT across a positive crossmatch. This allowed transplantation despite the presence of a positive crossmatch, with low rejection rates but potentially increased risk for major infections compared to the negative crossmatch controls on our standard protocol.

The Role of Humoral Alloreactivity in Liver Transplantation: Lessons Learned and New Perspectives

More than ten years after the initial description of the humoral theory of transplantation by Dr. Paul I. Terasaki, the significance of humoral alloimmunity in liver transplantation has yet to be clearly defined. The liver allograft has an inherent tolerogenic capacity which confers its resistance to cell-mediated as well as antibody-mediated rejection. Nevertheless, the protection against alloimmunity is not complete, and antibody-mediated tissue injury can occur in the liver graft under specific circumstances. In this article the evidence on the clinicopathologic effects of donor-specific alloantibodies in liver transplantation will be examined and interpreted in parallel with lessons learned from renal transplantation. The unique anatomic and immunologic features of the liver will be reviewed to gain new insights into the complex interactions between humoral immune system and the liver allograft.

Impact of donor-recipient genetic relationship on outcome of living donor liver transplantation

Living donor liver transplantation (LDLT) is a valuable option for expanding the donor pool, especially in localities where deceased organ harvesting is not allowed. In addition, rejection rates were found to be lower in LDLT, which is attributed to the fact that LDLT is usually performed between relatives. However, the impact of genetic relation on the outcome of LDLT has not been studied. In this study, we examined the difference in rejection rates between LDLT from genetically related (GR) donors and genetically unrelated (GUR) donors. All cases that underwent LDLT during the period from May 2004 until May 2014 were included in the study. The study group was divided into 2 groups: LDLT from GR donors and LDLT from GUR donors. A total of 308 patients were included in the study: 212 from GR donors and 96 from GUR donors. Human leukocyte antigen (HLA) typing was not included in the workup for matching donors and recipients. GUR donors were wives (36; 11.7%), sons-in-law (7; 2.3%), brothers-in-law (12; 3.9%), sisters-in-law (1; 0.3%), and unrelated (38; 12.3%). The incidence of acute rejection in the GR group was 17.4% and 26.3% in the GUR group (P value = 0.07). However, there was a significant difference in the incidence of chronic rejection (CR) between the 2 groups: 7% in GR group and 14.7% in the GUR group (P value = 0.03). In terms of overall survival, there was no significant difference between both groups. LDLT from the GUR donors is not associated with a higher incidence of acute cellular rejection. However, CR was significantly lower when grafts were procured from GR donors. HLA matching may be recommended before LDLT from GUR donors. Liver Transplantation 23:43-49 2017 AASLD.

De novo autoimmune hepatitis after liver transplantation: A focus on glutathione S-transferase theta 1

De novo autoimmune hepatitis (DAIH) is a rare clinical condition with features that resemble those of autoimmune hepatitis (AIH) in patients undergoing liver transplantation (LT) for nonautoimmune liver disease. The diagnosis of this entity has been based on the presence of biochemical and histological patterns similar to those observed in the primary AIH, although several considerations must be taken into account. The impact of DAIH on graft survival is relevant, and early diagnosis and treatment is associated with a good longterm outcome. Although glutathione S-transferase theta 1 (GSTT1) alloimmune recognition has been shown to be involved in the pathogenesis of DAIH, further studies are necessary to fully determine its pathogenic mechanisms and risk factors. We review the pathophysiology, the most common histological patterns, the treatment strategies, and the longterm outcomes of DAIH after LT with a special focus on GSTT1. Liver Transplantation 23:75-85 2017 AASLD.

Negative regulation of HLA-DR expression on endothelial cells by anti-blood group A/B antibody ligation and mTOR inhibition

Donor-specific antibody (DSA), particularly against HLA class II, is a major cause of chronic antibody-mediated rejection (CAMR) after transplantation, although ABO-incompatible kidney transplantation has recently demonstrated favorable graft outcomes. The condition of no injury even in the presence of anti-donor antibody has been referred to as "accommodation", which would be one of the key factors for successful long-term graft survival. The purpose of this study was to analyze the beneficial effect of anti-blood group A/B antibody ligation on endothelial cells against HLA-DR antibody-mediated, complement-dependent cytotoxicity (CDC). Blood group A/B-expressing endothelial cells EA.hy926 or Human Umbilical Vein Endothelia Cells (HUVEC) were incubated with IFNγ in the presence or absence of anti-blood group A/B antibody or mTOR inhibitor (mTOR-i) for 48h. The effects on signaling pathway, HLA expression, complement regulatory factors, and CDC were investigated. Expression of HLA-DR on EA.hy926 or HUVEC were successfully elicited by IFNγ treatment, although little or no expression was observed in quiescent cells. Pre-incubation with anti-blood group A/B antibody had resistance to HLA-DR antibody-mediated CDC against IFNγ-treated cells in a concentration-dependent manner. This finding was ascribed to decreased expression of HLA-DR by post-translational regulation and increased expression of CD55/59, which was related to ERK and mTOR pathway inhibition. mTOR-i also inhibited HLA-DR expression by itself. Furthermore, the combination of mTOR-I and anti-blood group A/B ligation had an additive effect in preventing HLA-DR antibody-mediated CDC. Anti-blood group A/B antibody might play a preventive role in CAMR. Inhibition of the ERK and mTOR pathways may contribute to the development of a novel treatment in the maintenance period after transplantation.

De novo donor-specific anti-HLA antibodies mediated rejection in liver-transplant patients

The incidence and consequences of de novo donor-specific anti-HLA antibodies (DSAs) after liver transplantation (LT) are not well known. We investigated the incidence, risk factors, and complications associated with de novo DSAs in this setting. A total of 152 de novo liver-transplant patients, without preformed anti-HLA DSAs, were tested for anti-HLA antibodies, with single-antigen bead technology, before, at transplantation, at 1, 3, 6 and 12 months after transplantation, and thereafter annually and at each time they presented with increased liver-enzyme levels until the last follow-up, that is, 34 (1.5-77) months. Twenty-one patients (14%) developed de novo DSAs. Of these, five patients had C1q-binding DSAs (24%). Younger age, low exposure to calcineurin inhibitors, and noncompliance were predictive factors for de novo DSA formation. Nine of the 21 patients (43%) with de novo DSAs experienced an acute antibody-mediated rejection (AMR). Positive C4d staining was more frequently observed in liver biopsies of patients with AMR (9/9 vs. 1/12, P < 0.0001). Eight patients received a B-cell targeting therapy, and one patient received polyclonal antibodies. Only one patient required retransplantation. Patient- and graft-survival rates did not differ between patients with and without DSAs. In conclusion, liver-transplant patients with liver abnormalities should be screened for DSAs and AMR.

Unraveling the Role of Allo-Antibodies and Transplant Injury

Alloimmunity driving rejection in the context of solid organ transplantation can be grossly divided into mechanisms predominantly driven by either T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR), though the co-existence of both types of rejections can be seen in a variable number of sampled grafts. Acute TCMR can generally be well controlled by the establishment of effective immunosuppression (1, 2). Acute ABMR is a low frequency finding in the current era of blood group and HLA donor/recipient matching and the avoidance of engraftment in the context of high-titer, preformed donor-specific antibodies. However, chronic ABMR remains a major complication resulting in the untimely loss of transplanted organs (3-10). The close relationship between donor-specific antibodies and ABMR has been revealed by the highly sensitive detection of human leukocyte antigen (HLA) antibodies (7, 11-15). Injury to transplanted organs by activation of humoral immune reaction in the context of HLA identical transplants and the absence of donor specific antibodies (17-24), strongly suggest the participation of non-HLA (nHLA) antibodies in ABMR (25). In this review, we discuss the genesis of ABMR in the context of HLA and nHLA antibodies and summarize strategies for ABMR management.

2016 Comprehensive Update of the Banff Working Group on Liver Allograft Pathology: Introduction of Antibody-Mediated Rejection

The Banff Working Group on Liver Allograft Pathology reviewed and discussed literature evidence regarding antibody-mediated liver allograft rejection at the 11th (Paris, France, June 5-10, 2011), 12th (Comandatuba, Brazil, August 19-23, 2013), and 13th (Vancouver, British Columbia, Canada, October 5-10, 2015) meetings of the Banff Conference on Allograft Pathology. Discussion continued online. The primary goal was to introduce guidelines and consensus criteria for the diagnosis of liver allograft antibody-mediated rejection and provide a comprehensive update of all Banff Schema recommendations. Included are new recommendations for complement component 4d tissue staining and interpretation, staging liver allograft fibrosis, and findings related to immunosuppression minimization. In an effort to create a single reference document, previous unchanged criteria are also included.

Prevention and treatment of liver allograft antibody-mediated rejection and the role of the 'two-hit hypothesis'

PURPOSE OF REVIEW

The review outlines the diagnosis, prevention strategies, and possible treatment options for acute and chronic antibody-mediated rejection (AMR).

RECENT FINDINGS

Although rare, severe acute AMR (aAMR) usually occurs in patients with high mean fluorescence intensity despite serial dilutions or high-titer preformed class I donor-specific alloantibodies (DSA). The diagnosis is suspected when allograft dysfunction occurs with DSA, diffuse C4d staining, and a microvascular injury, and may be aided by the aAMR score. However, the incidence of and treatment approach to combined T-cell-mediated rejection (TCMR) with DSA present and some but not all features of AMR is yet to be determined. Chronic liver allograft AMR is characterized by low-grade chronic inflammation and progressive fibrosis with DSA, the chronic AMR (cAMR) score may facilitate diagnosis. The 'two-hit' hypothesis, whereby a coexistent insult upregulates human leukocyte antigen class II target antigens on the microvascular endothelium, may explain why suboptimal donors with lower sensitization levels might suffer from acute AMR and those with chronic complications (e.g., recurrent original disease) might be more susceptible to chronic AMR. Although treatment algorithms are needed, prevention is preferable and at a minimum includes transfusion minimization, and medication adherence.

SUMMARY

Severe acute AMR is rare but diagnosable, and there is need to determine the incidence of and optimal therapy for less severe combined AMR and TCMR. Chronic AMR is likely more common and of significant relevance to long-term allograft survival improvement. The two-hit hypothesis may help to explain the rarity of both findings and shed insight onto future prevention and treatment strategies.

Protecting the Kidney in Liver Transplant Recipients: Practice-Based Recommendations From the American Society of Transplantation Liver and Intestine Community of Practice

Both acute and chronic kidney disease are common after liver transplantation and result in significant morbidity and mortality. The introduction of the Model for End-stage Liver Disease score has directly correlated with an increased prevalence of perioperative renal dysfunction and the number of simultaneous liver-kidney transplantations performed. Kidney dysfunction in this population is typically multifactorial and related to preexisting conditions, pretransplantation renal injury, perioperative events, and posttransplantation nephrotoxic immunosuppressive therapies. The management of kidney disease after liver transplantation is challenging, as by the time the serum creatinine level is significantly elevated, few interventions affect the course of progression. Also, immunological factors such as antibody-mediated kidney rejection have become of greater interest given the rising liver-kidney transplant population. Therefore, this review, assembled by experts in the field and endorsed by the American Society of Transplantation Liver and Intestine Community of Practice, provides a critical assessment of measures of renal function and interventions aimed at preserving renal function early and late after liver and simultaneous liver-kidney transplantation. Key points and practice-based recommendations for the prevention and management of kidney injury in this population are provided to offer guidance for clinicians and identify gaps in knowledge for future investigations.

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Donor-specific HLA Antibodies Are Associated With Late Allograft Dysfunction After Pediatric Liver Transplantation

BACKGROUND

The role of donor-specific HLA antibodies (DSA) after pediatric liver transplantation (LTx) is not clearly established. We completed a cross-sectional study to characterize DSA in long-term survivors of pediatric LTx and assess the impact of C1q-binding DSA on allograft outcomes.

METHODS

Serum samples were collected at routine clinic visits from 50 pediatric LTx recipients classified into 3 clinical phenotypes: nontolerant (n = 18) with de novo autoimmune hepatitis (DAIH) and/or late acute cellular rejection (ACR); stable (n = 25) on maintenance tacrolimus; operationally tolerant (n = 7). Samples were blinded, and antibody detection was performed using Luminex single antigen class I and II beads. Patients with positive DSA were tested for C1q-binding DSA.

RESULTS

DSA were detected in 54% (n = 27) of the patients, with the majority directed at HLA class II antigens (DR, 41%; DQ, 53%). Patients with DSA were younger at the time of LTx (P = 0.016) and time of study (P = 0.024). Mean aspartate aminotransferase, alanine aminotransferase, total bilirubin, and gamma glutamyl transferase were higher in DSA-positive patients, though did not reach statistical significance. Nontolerant patients were significantly more likely to have DQ DSA (61%) compared to stable (20%) and tolerant (29%) patients (P = 0.021). The nontolerant phenotype was associated with DSA and C1q-binding DSA, with odds ratios of 13 (P = 0.015) and 8.6 (P = 0.006), respectively. The presence of DQ DSA was associated with DAIH and late ACR, with odds ratios of 12.5 (P = 0.004) and 10.8 (P = 0.006), respectively.

CONCLUSIONS

Allograft dysfunction is not always evident in patients with DSA, but DQ DSA are strongly associated with DAIH, late ACR, and chronic rejection.

The Influence of Immunosuppressive Agents on the Risk of De Novo Donor-Specific HLA Antibody Production in Solid Organ Transplant Recipients

Production of de novo donor-specific antibodies (dnDSA) is a major risk factor for acute and chronic antibody-mediated rejection and graft loss after all solid organ transplantation. In this article, we review the data available on the risk of individual immunosuppressive agents and their ability to prevent dnDSA production. Induction therapy with rabbit antithymocyte globulin may achieve a short-term decrease in dnDSA production in moderately sensitized patients. Rituximab induction may be beneficial in sensitized patients, and in abrogating rebound antibody response in patients undergoing desensitization or treatment for antibody-mediated rejection. Use of bortezomib for induction therapy in at-risk patients is of interest, but the benefits are unproven. In maintenance regimens, nonadherent and previously sensitized patients are not suitable for aggressive weaning protocols, particularly early calcineurin inhibitor withdrawal without lymphocyte-depleting induction. Early conversion to mammalian target of rapamycin inhibitor monotherapy has been reported to increase the risk of dnDSA formation, but a combination of mammalian target of rapamycin inhibitor and reduced-exposure calcineurin inhibitor does not appear to alter the risk. Early steroid therapy withdrawal in standard-risk patients after induction has no known dnDSA penalty. The available data do not demonstrate a consistent effect of mycophenolic acid on dnDSA production. Risk minimization for dnDSA requires monitoring of adherence, appropriate risk stratification, risk-based immunosuppression intensity, and prospective DSA surveillance.

Long-Term Outcomes of Living-Donor Liver Transplantation for Primary Biliary Cirrhosis: A Japanese Multicenter Study

The factors that influence long-term outcomes after living-donor liver transplantation (LDLT) for primary biliary cirrhosis (PBC) are not well known. Compared with deceased-donor transplantation, LDLT has an increased likelihood of a related donor and a decreased number of human leukocyte antigen (HLA) mismatches. To clarify the effects of donor relatedness and HLA mismatch on the outcomes after LDLT, we retrospectively analyzed 444 Japanese patients. Donors were blood relatives for 332 patients, spouses for 105, and "other" for 7. The number of HLA A-B-DR mismatches was none to two in 141, three in 123, and four to six in 106 patients. The 15-year survival rate was 52.6%, and PBC recurred in 65 patients. Recipient aged 61 years or older, HLA mismatches of four or more (maximum of six), graft:recipient weight ratio less than 0.8, and husband donor were adverse indicators of patient survival. IgM 554 mg/dL or greater, donor-recipient sex mismatch, and initial immunosuppression with cyclosporine were significant risks for PBC recurrence, which did not affect patient survival. In subgroup analysis, conversion to cyclosporine from tacrolimus within 1 year diminished recurrence. Prospective studies are needed to determine the influence of pregnancy-associated sensitization and to establish an optimal immunosuppressive regimen in LDLT patients.

Donor-specific antibodies and liver transplantation

In contrast to other types of organ transplantation, liver-transplant recipients used to be considered highly resistant to donor-specific antibodies (DSAs). Consequently, most transplant programs did not consider the presence of DSAs at transplantation or during the follow-up. However, since the early 1990s, antibody-mediated pathological lesions have been recognized in ABO-incompatible liver-transplant recipients. Recent data confirm the detrimental effect of preformed and de novo DSAs in ABO-compatible liver transplantation, with inferior clinical outcomes in patients presenting with circulating antibodies. Acute antibody-mediated rejection (AMR), plasma-cell hepatitis, biliary stricture, but also long-term complications, such as chronic rejection, liver ductopenia, and graft fibrosis, are now recognized to be associated with DSAs. Moreover, some non-HLA DSAs are suspected to induce graft dysfunction. Clinical, biological, and histological patterns within AMR need to be clarified. Treatment of these complications has yet to be defined. This article summarizes recent advances concerning the impact of preformed and de novo DSAs in liver transplantation, it defines the complications associated with DSAs, and discusses the potential strategies to manage patients with such complications.

Donor-specific antibodies after pediatric liver transplantation: a cross-sectional study of 50 patients

The role of donor-specific HLA antibodies (DSAs) after pediatric liver transplantation (LT) is inadequately established. We conducted a cross-sectional study on the prevalence of DSAs and their association with liver histology and biochemical variables after pediatric LT. Serum samples were drawn for HLA antibody analyses from 50 patients (76% of 66 eligible patients) operated on at age <18 years between 1987 and 2007 with a median of 10.0 (interquartile range 4.0-16.4) years after deceased donor LT. Mixed and single-antigen beads with Luminex were used for HLA antibody screening and detection. A mean fluorescence intensity (MFI) value of 1000 was used for positive cutoff. Twenty-six patients (52%; 95% confidence interval (CI) 39% to 65%) had DSAs. In 22 (85%) patients, DSAs were against class II HLA antigens with a mean (standard deviation) MFI of 13,481 (4727). The unadjusted prevalence ratio for portal inflammation in DSA-positive compared to DSA-negative patients (n = 47; 9/24 vs. 1/23) was 8.6 (95% CI 1.6 to 50.9). Laboratory values at the time of study were comparable between DSA-positive and DSA-negative patients. In conclusion, approximately half of patients studied had DSAs after pediatric LT. Portal inflammation was associated with DSA positivity although the wide confidence interval around the ratio estimate warrants cautious interpretation.

Effect of Immunosuppressive Drugs on Humoral Allosensitization after Kidney Transplant

The negative effect of donor-specific antibodies on the success of solid transplant is now clearly established. However, the lack of effective treatment to prevent the development of antibody-mediated lesions deepens the need for clinicians to focus on primary prevention of de novo humoral allosensitization. Among the factors associated with the risk of developing de novo donor-specific antibodies, therapeutic immunosuppression is the most obvious parameter in which improvement is possible. Beyond compliance and the overall depth of immunosuppression, it is likely that the nature of the drugs is also crucial. Here, we provide an overview of the molecular effect of the various immunosuppressive drugs on B cell biology. Clinical data related to the effect of these drugs on de novo humoral allosensitization are also examined, providing a platform from which clinicians can optimize immunosuppression for prevention of de novo donor-specific antibody generation at the individual level.

Alloantibody Generation and Effector Function Following Sensitization to Human Leukocyte Antigen

Allorecognition is the activation of the adaptive immune system to foreign human leukocyte antigen (HLA) resulting in the generation of alloantibodies. Due to a high polymorphism, foreign HLA is recognized by the immune system following transplant, transfusion, or pregnancy resulting in the formation of the germinal center and the generation of long-lived alloantibody-producing memory B cells. Alloantibodies recognize antigenic epitopes displayed by the HLA molecule on the transplanted allograft and contribute to graft damage through multiple mechanisms, including (1) activation of the complement cascade resulting in the formation of the MAC complex and inflammatory anaphylatoxins, (2) transduction of intracellular signals leading to cytoskeletal rearrangement, growth, and proliferation of graft vasculature, and (3) immune cell infiltration into the allograft via FcγR interactions with the FC portion of the antibody. This review focuses on the generation of HLA alloantibody, routes of sensitization, alloantibody specificity, and mechanisms of antibody-mediated graft damage.