Determinants of poor graft outcome in patients with antibody-mediated acute rejection

Higher Donor Age and Severe Microvascular Inflammation Are Risk Factors for Chronic Rejection After Treatment of Active Antibody-Mediated Rejection

Recent developments in intensive desensitization protocols have enabled kidney transplantation in human leukocyte antigen (HLA)-sensitized recipients. However, cases of active antibody-mediated rejection (AABMR), when they occur, are difficult to manage, graft failure being the worst-case scenario. We aimed to assess the impact of our desensitization and AABMR treatment regimen and identify risk factors for disease progression. Among 849 patients who underwent living-donor kidney transplantation between 2014 and 2021 at our institution, 59 were diagnosed with AABMR within 1 year after transplantation. All patients received combination therapy consisting of steroid pulse therapy, intravenous immunoglobulin, rituximab, and plasmapheresis. Multivariable analysis revealed unrelated donors and preformed donor-specific antibodies as independent risk factors for AABMR. Five-year death-censored graft survival rate was not significantly different between patients with and without AABMR although 27 of 59 patients with AABMR developed chronic AABMR (CABMR) during the study period. Multivariate Cox proportional hazard regression analysis revealed that a donor age greater than 59 years and microvascular inflammation (MVI) score (g + ptc) ≥4 at AABMR diagnosis were independent risk factors for CABMR. Our combination therapy ameliorated AABMR; however, further treatment options should be considered to prevent CABMR, especially in patients with old donors and severe MVI.

Complement and Non-Complement Binding Anti-HLA Antibodies Are Differentially Detected with Different Antigen Bead Assays in Renal Transplant Recipients

Two semi-quantitative, Luminex-based, single-antigen bead (SAB) assays are available to detect anti-HLA antibodies and evaluate their reactivity with complement binding. Sera from 97 patients with positive panel reactive antibody tests (>5%) were analyzed with two SAB tests, Immucor (IC) and One-Lambda (OL), for anti-HLA antibody detection and the evaluation of their complement-binding capacity. IC detected 1608/8148 (mean fluorescent intensity (MFI) 4195 (1995-11,272)) and 1136/7275 (MFI 6706 (2647-13,184)) positive anti-HLA class I and II specificities, respectively. Accordingly, OL detected 1942/8148 (MFI 6185 (2855-12,099)) and 1247/7275 (MFI 9498 (3630-17,702)) positive anti-HLA class I and II specificities, respectively. For the IC assay, 428/1608 (MFI 13,900 (9540-17,999)) and 409/1136 (MFI 11,832 (7128-16,531)) positive class I and II specificities bound C3d, respectively. Similarly, OL detected 485/1942 (MFI 15,452 (9369-23,095)) and 298/1247 (MFI18,852 (14,415-24,707)) C1q-binding class I and II specificities. OL was more sensitive in detecting class I and II anti-HLA antibodies than IC was, although there was no significant difference in the number of class II specificities per case. MFI was higher for complement vs. non-complement-binding anti-HLA antibodies in both assays. Both methods were equal in detecting complement-binding anti-HLA class I antibodies, whereas the C3d assay was more sensitive in detecting complement-binding anti-HLA class II antibodies.

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

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

Early Versus Late Acute AMR in Kidney Transplant Recipients-A Comparison of Treatment Approaches and Outcomes From the ANZDATA Registry

BACKGROUND

Antibody-mediated rejection (AMR) is a major cause of kidney allograft failure and demonstrates different properties depending on whether it occurs early (<6 mo) or late (>6 mo) posttransplantation. We aimed to compare graft survival and treatment approaches for early and late AMR in Australia and New Zealand.

METHODS

Transplant characteristics were obtained for patients with an AMR episode reported to the Australia and New Zealand Dialysis and Transplant Registry from January 2003 to December 2019. The primary outcome of time to graft loss from AMR diagnosis, with death considered a competing risk, was compared between early and late AMR using flexible parametric survival models. Secondary outcomes included treatments used, response to treatment, and time from AMR diagnosis to death.

RESULTS

After adjustment for other explanatory factors, late AMR was associated with twice the risk of graft loss relative to early AMR. The risk was nonproportional over time, with early AMR having an increased early risk. Late AMR was also associated with an increased risk of death. Early AMR was treated more aggressively than late with more frequent use of plasma exchange and monoclonal/polyclonal antibodies. There was substantial variation in treatments used by transplant centers. Early AMR was reported to be more responsive to treatment than late.

CONCLUSIONS

Late AMR is associated with an increased risk of graft loss and death compared with early AMR. The marked heterogeneity in the treatment of AMR highlights the need for effective, new therapeutic options for these conditions.

The Clinical Utility of Post-Transplant Monitoring of Donor-Specific Antibodies in Stable Renal Transplant Recipients: A Consensus Report With Guideline Statements for Clinical Practice

Solid phase immunoassays improved the detection and determination of the antigen-specificity of donor-specific antibodies (DSA) to human leukocyte antigens (HLA). The widespread use of SPI in kidney transplantation also introduced new clinical dilemmas, such as whether patients should be monitored for DSA pre- or post-transplantation. Pretransplant screening through SPI has become standard practice and DSA are readily determined in case of suspected rejection. However, DSA monitoring in recipients with stable graft function has not been universally established as standard of care. This may be related to uncertainty regarding the clinical utility of DSA monitoring as a screening tool. This consensus report aims to appraise the clinical utility of DSA monitoring in recipients without overt signs of graft dysfunction, using the Wilson & Junger criteria for assessing the validity of a screening practice. To assess the evidence on DSA monitoring, the European Society for Organ Transplantation (ESOT) convened a dedicated workgroup, comprised of experts in transplantation nephrology and immunology, to review relevant literature. Guidelines and statements were developed during a consensus conference by Delphi methodology that took place in person in November 2022 in Prague. The findings and recommendations of the workgroup on subclinical DSA monitoring are presented in this article.

Microvascular inflammation in the absence of human leukocyte antigen-donor-specific antibody and C4d: An orphan category in Banff classification with cytotoxic T and natural killer cell infiltration

Isolated microvascular inflammation (iMVI) without HLA donor-specific antibodies or C4d deposition in peritubular capillaries remains an enigmatic phenotype that cannot be categorized as antibody-mediated rejection (ABMR) in recent Banff classifications. We included 221 kidney transplant recipients with biopsies with ABMR (n = 73), iMVI (n = 32), and normal (n = 116) diagnoses. We compared peripheral blood leukocyte distribution by flow cytometry and inflammatory infiltrates in kidney transplant biopsies among groups. Flow cytometry showed fewer lymphocytes and total, CD4+, and CD8+ peripheral T cells in iMVI compared with ABMR and normal cases. ABMR and iMVI had fewer total natural Killer (NK) cells but more NKG2A+ NK cells. Immunohistochemistry indicated that ABMR and iMVI had greater CD3+ and CD68+ glomerular infiltration than normal biopsies, whereas CD8+ and TIA1+ cells showed only increased iMVI, suggesting they are cytotoxic T cells. Peritubular capillaries displayed more CD3+, CD56+, TIA1+, and CD68+ cells in both ABMR and iMVI. In contrast, iMVI had less plasma cell infiltration in peritubular capillaries and interstitial aggregates than ABMR. iMVI displayed decreased circulating T and NK cells mirrored by T cell and NK cell infiltration in the renal allograft, similar to ABMR. However, the lesser plasma cell infiltration in iMVI may suggest an antibody-independent underlying stimulus.

Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion

BACKGROUND

Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation.

METHODS

Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54 h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600 μg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1 + 2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition.

FINDINGS

Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition.

INTERPRETATION

We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR.

FUNDING

The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Inhibition of spleen tyrosine kinase decreases donor specific antibody levels in a rat model of sensitization

Antibody mediated rejection is a major cause of renal allograft loss. Circulating preformed donor specific antibodies (DSA) can result as a consequence of blood transfusion, pregnancy or prior transplantation. Current treatment strategies are limited due to partial or transient efficacy, adverse side-effects or patient unsuitability. Previous in vivo studies exploring autoimmune diseases have shown that spleen tyrosine kinase (SYK) signalling is involved in the development of pathogenic autoantibody. The role of SYK in allogenic antibody production is unknown, and we investigated this in a rodent model of sensitization, established by the transfusion of F344 whole blood into LEW rats. Two-week treatment of sensitized rats with selective SYK inhibitor fostamatinib strongly blocked circulating DSA production without affecting overall total immunoglobulin levels, and inhibition was sustained up to 5 weeks post-completion of the treatment regimen. Fostamatinib treatment did not affect mature B cell subset or plasma cell levels, which remained similar between non-treated controls, vehicle treated and fostamatinib treated animals. Our data indicate fostamatinib may provide an alternative therapeutic option for patients who are at risk of sensitization following blood transfusion while awaiting renal transplant.

Recipient myeloperoxidase-producing cells regulate antibody-mediated acute versus chronic kidney allograft rejection

Antibody-mediated rejection (ABMR) continues to be a major problem undermining the success of kidney transplantation. Acute ABMR of kidney grafts is characterized by neutrophil and monocyte margination in the tubular capillaries and by graft transcripts indicating NK cell activation, but the myeloid cell mechanisms required for acute ABMR have remained unclear. Dysregulated donor-specific antibody (DSA) responses with high antibody titers are induced in B6.CCR5-/- mice transplanted with complete MHC-mismatched A/J kidneys and are required for rejection of the grafts. This study tested the role of recipient myeloid cell production of myeloperoxidase (MPO) in the cellular and molecular components of acute ABMR. Despite induction of equivalent DSA titers, B6.CCR5-/- recipients rejected A/J kidneys between days 18 and 25, with acute ABMR, whereas B6.CCR5-/-MPO-/- recipients rejected the grafts between days 46 and 54, with histopathological features of chronic graft injury. On day 15, myeloid cells infiltrating grafts from B6.CCR5-/- and B6.CCR5-/-MPO-/- recipients expressed marked phenotypic and functional transcript differences that correlated with the development of acute versus chronic allograft injury, respectively. Near the time of peak DSA titers, activation of NK cells to proliferate and express CD107a was decreased within allografts in B6.CCR5-/-MPO-/- recipients. Despite high titers of DSA, depletion of neutrophils reproduced the inhibition of NK cell activation and decreased macrophage infiltration but increased monocytes producing MPO. Overall, recipient myeloid cells producing MPO regulate graft-infiltrating monocyte/macrophage function and NK cell activation that are required for DSA-mediated acute kidney allograft injury, and their absence switches DSA-mediated acute pathology and graft outcomes to chronic ABMR.

Reducing Donor-specific Antibody During Acute Rejection Diminishes Long-term Renal Allograft Loss: Comparison of Early and Late Rejection

BACKGROUND

Reduction in donor-specific antibody (DSA) has been associated with improved renal allograft survival after antibody-mediated rejection (AMR). These observations have not been separately analyzed for early and late AMR and mixed acute rejection (MAR). The purpose of this study was to evaluate long-term responses to proteasome inhibitor-based therapy for 4 rejection phenotypes and to determine factors that predict allograft survival.

METHODS

Retrospective cohort study evaluating renal transplant recipients with first AMR episodes treated with proteasome inhibitor-based therapy from January 2005 to July 2015.

RESULTS

A total of 108 patients were included in the analysis. Immunodominant DSA reduction at 14 days differed significantly (early AMR 79.6%, early MAR 54.7%, late AMR 23.4%, late MAR 21.1%, P < 0.001). Death-censored graft survival (DCGS) differed at 3 years postrejection (early AMR 88.3% versus early MAR 77.8% versus late AMR 56.7% versus late MAR 54.9%, P = 0.02). Multivariate analysis revealed that immunodominant DSA reduction > 50% at 14 days was associated with improved DCGS (odds ratio, 0.12, 95% CI, 0.02-0.52, P = 0.01).

CONCLUSIONS

In summary, significant differences exist across rejection phenotypes with respect to histological and DSA responses. The data suggest that DSA reduction may be associated with improved DCGS in both early and late AMR.

Kidney Transplant Graftectomy by Severe Mixed-Type Rejection with Acute and Chronic Active Vascular Lesions at Entire Levels of the Renal Vasculature

Vascular lesions related to allograft rejection have a big impact on graft survival. As such, investigation of these lesions is important to understand the pathophysiology of rejection and its management. We report a case of kidney transplant graftectomy by severe mixed-type rejection with acute and chronic active vascular lesions caused by non-adherence to immunosuppressive treatment. The patient presented is a 29-year-old male who received a kidney transplantation in July 2011 (ABO compatible) from his father. He then did not come to the hospital for 3 months prior to his admission and also made his own decision to stop his medication regimen. On October 2013, the patient came to the hospital with dyspnea, nausea, and vomiting and had significant renal dysfunction (serum Cr 30.4 mg/dL, BUN 191 mg/dL). A kidney graft biopsy showed cortical necrosis with severe interstitial hemorrhage and thrombotic microangiopathy (TMA). Despite steroid pulse therapy, kidney graft function did not recover, and the patient underwent a subsequent graft resection. The resected kidney graft displayed various vascular lesions from the renal artery to the interlobular arteries and arterioles including endarteritis, TMA, fibrinoid necrosis, and transplant arteriopathy. This case shows the detailed pathological findings of the vascular lesions in the entire artery tree of kidney allograft, and the pathophysiology is discussed.

Kidney Rejection Following Simultaneous Liver-kidney Transplantation

Background.

Donor-specific antibodies are reported to increase the risk of rejection and reduce allograft survival following simultaneous liver-kidney transplantation. Optimal immunosuppression regimens to reduce this risk and to treat rejection episodes are underinvestigated.

Methods.

Cohort analysis of the first 27 simultaneous liver-kidney transplant recipients, between 2014 and 2018 at our unit, is performed under a new risk stratification policy. Those with donor-specific antibodies to class II HLA with a mean fluorescence intensity >10 000 are considered high risk for antibody-mediated rejection (AMR). These patients received immunosuppression, which consisted of induction therapy, tacrolimus, mycophenolate mofetil, and prednisolone. All other patients are considered low risk and received tacrolimus and prednisolone alone.

Results.

Three patients were high risk for rejection, and 2 of these patients developed AMR, which was treated with plasma exchange and intravenous immunoglobulin. At 1 y, their estimated glomerular filtration rate (eGFR) were 50 and 59 mL/min. Two other patients developed AMR, which was similarly treated, and their 1-y eGFR was 31 and 50 mL/min. The overall histologically proven acute rejection rate within the first year was 33%, and median eGFR, for the 27 patients, at 1 y was 52 mL/min and at 2 y was 49 mL/min.

Conclusions.

This study confirms that there is a risk of AMR following simultaneous liver-kidney transplantation despite increased immunosuppression. This can be effectively treated with plasma exchange and intravenous immunoglobulin.

The Preliminary Results of Bortezomib Used as A Primary Treatment for An Early Acute Antibody-Mediated Rejection after Kidney Transplantation-A Single-Center Case Series

Proteasome inhibitor bortezomib has been used in the treatment of refractory cases of acute and chronic antibody-mediated rejection (AMR) in kidney transplant recipients. However, its efficacy and safety as a primary treatment for early AMR has been scarcely investigated. We herein present our preliminary experience with bortezomib- and plasmapheresis-based primary treatment for early AMR. Thirteen patients transplanted between October 2015 and September 2019 were treated (starting at median 19th post-transplant day) with bortezomib/plasmapheresis protocol for early biopsy-proven AMR. Twelve out of thirteen patients received 4 doses and one patient recieved 3 doses of bortezomib (1.3 mg/m² per dose). In 11/13 patients, 4–7 concomitant plasmapheresis sessions were performed, with or without intravenous immunoglobulin (IVIG). Of note, rituximab was not used in all study patients. The kidney graft and patient survival were 100%. The mean 3-month estimated glomerular filtration rate (eGFR) was 55.3 (95%CI: 44.9–65.8) mL/min/1.73m², 8/13 patients completed 12-month follow-up with mean eGFR 60.4 (45.4–75.4) mL/min/1.73m², and 6/13 patients completed a 24-month follow-up period with mean eGFR 73.9 (56.7–91.1) mL/min/1.73m². Neutropenia < 1 G/L was observed in one patient, third or fourth grade thrombocytopenia in two patients, and eleven patients needed a blood transfusion (median: 2 units/patient). The mid-term results of a primary bortezomib-based treatment for kidney AMR showed its non-inferiority as compared to preceding regimens and acceptable safety. However, our data should be validated in a multicenter randomized trial.

Quantitative analysis of humoral immunity by flow-cytometric crossmatch using molecules of equivalent soluble fluorochromosome (FCXM-MESF)

OBJECTIVES

In this study, we examined the quantitative significance of humoral immunity by flow-cytometric crossmatch using molecules of equivalent soluble fluorochromosome (FCXM-MESF) in recipients of kidney transplantation. We stratified the recipients into four sensitization classes, from non-sensitized to strongly sensitized by the results of the FCXM-MESF assay, and compared the pathological results after transplantation by the sensitization status.

MATERIALS AND METHODS

We stratified 140 recipients into four groups according to their sensitization status, as follows; none/NDSA, defined by FCXM-MESF values of below the cut-off value (n = 79), mildly sensitized, defined by FCXM-MESF values of less than 3000 (N = 45); moderately sensitized, defined by FCXM-MESF values of between 3000 and 8000 (N = 12); strongly sensitized, defined by FCXM-MESF values exceeding 8000 (N = 4).

RESULTS

We employed tailor-made immunosuppressive regimens according to the FCXM-MESF values for the 140 recipients between 2009 and 2011. In regard to the pathological results, 4% (2/51), 3% (1/35), 20% (2/10) and 75% (3/4) of the none/Non Donor Specific Antibody (NDSA), mildly sensitized, moderately sensitized and strongly sensitized patients showed antibody mediated rejection (AMR). Thus, FCXM may be more useful for the detection of anti-non-HLA as well as for that of anti-HLA antibodies than the solid phase assay (SPA) or panel reactive antibody (PRA) assay.

CONCLUSION

Quantitative analysis using FCXM-MESF assay accurately reflected the clinical as well as pathological aspects, and may serve as a useful guide for the selection of appropriate anti-rejection therapy.

In situ multiplex immunofluorescence analysis of the inflammatory burden in kidney allograft rejection: A new tool to characterize the alloimmune response

Background: The exact composition and localization of the inflammatory burden during allograft rejection is difficult to analyse on the same biopsy slide. We tested the feasibility of detecting four distinct markers in a same paraffin-embedded tissue section from human kidney allograft rejection by using an innovative process of multiplex immunofluorescence. Methods: Kidney allograft biopsies from 20 antibody-mediated rejection, 20 T cell-mediated rejection and five non rejection were labelled against NKp46, CD163, CD3, and CD34 respectively for NK cells, macrophages, T cells and endothelial cells. Images were scanned and cells were automatically quantified and their extra- or intravascular location determined. Conventional immunohistochemistry against NKp46 with manual quantification and real time quantitative polymerase chain reaction for evaluation of the relative messenger ribonucleic acid (mRNA) expression levels of NK, T cell and macrophage transcripts were simultaneously performed. Results: Multiplex immunofluorescence cell quantification was strongly correlated to manual quantification by immunohistochemistry (r = 0.91, P < 0.001) and to mRNA expression levels (r > 0.46, P < 0.021). T cells and macrophages were the two predominant populations involved in rejection (48.0 ± 4.4% and 49.3 ± 4.4% in antibody-mediated rejection; 51.8 ± 6.0% and 45.3 ± 5.8% in T cell-mediated rejection respectively) despite an important heterogeneity in the composition of the inflammatory burden. NK cells constituted a rare population for both T cell-mediated rejection (2.9 ± 0.6%) and antibody-mediated rejection (2.7 ± 0.7%). The intravascular compartment was mainly composed of T cells, including during antibody-mediated rejection. However, NK cells and macrophages densities were significantly higher in capillaries during antibody-mediated rejection. Conclusion: Multiplex immunofluorescence staining is a reliable technology allowing studying the exact composition and localization of the inflammatory burden during kidney allograft rejection..

C5b9 Deposition in Glomerular Capillaries Is Associated With Poor Kidney Allograft Survival in Antibody-Mediated Rejection

C4d deposition in peritubular capillaries (PTC) reflects complement activation in antibody-mediated rejection (ABMR) of kidney allograft. However, its association with allograft survival is controversial. We hypothesized that capillary deposition of C5b9-indicative of complement-mediated injury-is a severity marker of ABMR. This pilot study aimed to determine the frequency, location and prognostic impact of these deposits in ABMR. We retrospectively selected patients diagnosed with ABMR in two French transplantation centers from January 2005 to December 2014 and performed C4d and C5b9 staining by immunohistochemistry. Fifty-four patients were included. Median follow-up was 52.5 (34.25-73.5) months. Thirteen patients (24%) had C5b9 deposits along glomerular capillaries (GC). Among these, seven (54%) had a global and diffuse staining pattern. Twelve of the C5b9+ patients also had deposition of C4d in GC and PTC. C4d deposits along GC and PTC were not associated with death-censored allograft survival (p = 0.42 and 0.69, respectively). However, death-censored allograft survival was significantly lower in patients with global and diffuse deposition of C5b9 in GC than those with a segmental pattern or no deposition (median survival after ABMR diagnosis, 6 months, 40.5 months and 44 months, respectively; p = 0.015). Double contour of glomerular basement membrane was diagnosed earlier after transplantation in C5b9+ ABMR than in C5b9- ABMR (median time after transplantation, 28 vs. 85 months; p = 0.058). In conclusion, we identified a new pattern of C5b9+ ABMR, associated with early onset of glomerular basement membrane duplication and poor allograft survival. Complement inhibitors might be a therapeutic option for this subgroup of patients.

Antibody-mediated rejection implies a poor prognosis in kidney transplantation: Results from a single center

Two major barriers to achieving long-term graft survival include patient nonadherence in taking the prescribed immunosuppression and antibody-mediated rejection(AMR). We were therefore interested in determining the prognostic impact of developing an AMR component to rejection in a prospective randomized trial of 200 kidney transplant recipients who received dual induction therapy (rATG combined with either daclizumab or alemtuzumab) and planned early corticosteroid withdrawal. With a median follow-up of 96 months post-transplant, 40/200 developed a first BPAR; 9/200 developed a second BPAR. An AMR component to rejection was observed in 70% (28/40) of cases. Percentages having C4d deposition, histopathologic evidence of acute AMR, and presence of DSAs/non-DSAs at the time of first developing the AMR component were 64.3% (18/28), 60.7% (17/28), and 53.6% (15/28), respectively. Development of an AMR component was associated with a significantly higher death-censored graft failure rate following rejection in comparison with the patient state of experiencing BPAR but without developing an AMR component (estimated hazard ratio: 4.52, P = 0.01). The observed percentage developing graft failure following development of an AMR component was 53.6% (15/28) vs only 20.0%(3/15) if it was not observed. Actuarial death-censored graft survival at 60 months following development of an AMR component was 28.3 ± 11.9%. In summary, it appears that more effective AMR prevention/treatment strategies are warranted.

Isolated v-lesion represents a benign phenotype of vascular rejection of the kidney allograft - a retrospective study

While the detrimental impact of the humoral acute vascular rejection (AVR) phenotype is recognized, the prognostic significance of isolated v-lesion (IV) remains unclear. In this retrospective single-centre study, AVR was found in 98 of 1015 patients (9.7%) who had undergone kidney transplantation in 2010-2014, with donor-specific antibodies (DSA) evaluated in all of them. The outcome of four AVR phenotypes was evaluated during median follow-up of 59 months; in 25 patients with IV, 18 with T-cell-mediated vascular rejection (TCMVR), 19 with antibody-mediated vascular rejection (AMVR) and 36 with suspected antibody-mediated rejection (sAMVR). AVR was diagnosed mainly by for-cause biopsy (81%) early after transplantation (median 19 POD) and appeared as mild-grade intimal arteritis. IV occurred in low-sensitized patients after the first transplantation (96%) in the absence of DSA. IV responded satisfactorily to treatment (88%), showed no persistence of rejection in surveillance biopsy, and had stable graft function, minimal proteinuria and excellent DCGS (96%). Contrary to that, Kaplan-Meier estimate of 3-year DCGS of AMVR was 66% (log-rank = 0.0004). Early IV represents a benign phenotype of AVR with a favourable outcome. This study prompts further research to evaluate the nature of IV before considering any change in the classification and management.

Dynamic Prognostic Score to Predict Kidney Allograft Survival in Patients with Antibody-Mediated Rejection

No tool is available for the early assessment of response to antibody-mediated rejection (ABMR) therapies in kidney allograft recipients. This study was designed to define a dynamic composite prognostic ABMR score to predict kidney allograft survival, integrating the disease characteristics at diagnosis and the response to treatment. Among 1978 kidney recipients who underwent transplant between 2008 and 2014, we included 278 patients diagnosed with active ABMR and receiving standard treatment, including plasma exchange, intravenous Ig, and rituximab. Patients were prospectively assessed at diagnosis and after treatment for clinical data, histologic characteristics (allograft biopsy specimen), and donor-specific anti-HLA antibodies (DSA). The dynamic ABMR prediction model included GFR (P<0.001) and presence of interstitial fibrosis/tubular atrophy (P=0.003) at diagnosis and changes in GFR (P<0.001), peritubular capillaritis Banff score (P=0.002), and DSA mean fluorescence intensity (P<0.001) after treatment. Overall, this model showed good calibration and discrimination (C-statistic=0.84). The ABMR prognostic score derived from the prediction model identified three risk strata with 6-year kidney allograft survival rates of 6.0% (high-risk group, n=40), 44.9% (intermediate-risk group, n=36), and 84.4% (low-risk group, n=202), and it provided greater net clinical benefit to patients than did considering them all to have the same level of risk of allograft loss. The performance of the ABMR prognostic score was validated in an independent cohort of 202 kidney recipients with ABMR (C-statistic=0.79). The ABMR prognostic score could be used to inform therapeutic decisions in clinical practice and for the design of clinical trials.

Evidence for an important role of both complement-binding and noncomplement-binding donor-specific antibodies in renal transplantation

PURPOSE OF REVIEW

The review describes the current clinical relevance of circulating anti-human leukocyte antigen (anti-HLA) antibodies in kidney transplantation and discusses recent improvements in their characterization that provide new insights into the identification and management of important clinical outcomes.

RECENT FINDINGS

Recent studies addressing the relationships between donor-specific anti-HLA antibody (HLA-DSA) properties (i.e., their strength, complement-binding capacity, and IgG subclass composition) and allograft injury and survival have highlighted their relevance in the prediction of antibody-mediated injury and allograft loss.

SUMMARY

Antibody-mediated rejection is the leading cause of kidney allograft loss. Although considerable experimental and clinical evidence suggests a causal effect of circulating HLA-DSAs in antibody-mediated rejection and allograft failure, HLA-DSAs induce a wide spectrum of injuries to the allograft that illustrate the need to delineate the characteristics of HLA-DSAs that confer pathogenesis. Current risk stratification is based on HLA-DSA characteristics, including antibody specificity, HLA class, and strength. Recently, the complement-binding capacity of HLA-DSAs has been recognized as a clinically relevant marker for predicting pathogenicity and allograft loss. Emerging data also support a role for HLA-DSA IgG subclass composition in discriminating distinct patterns of antibody-mediated injury. This progress in our understanding of HLA-DSA pathogenicity provides new tools to stratify individual immunological risks. However, specific prospective studies addressing immunological risk stratification in large and unselected populations are required to define the clinical benefit and cost-effectiveness of such a comprehensive assessment of HLA-DSAs before implementation in current clinical practice.

An integrated view of immune monitoring in vascularized composite allotransplantation

PURPOSE OF REVIEW

Vascularized composite allotransplantation (VCA) has several immunological peculiarities that imply a specific immune monitoring. Here, we provide an integrated view of current procedures of immune monitoring in VCA and potential complementary approaches learned from organ transplantation.

RECENT FINDINGS

Because the skin is highly immunogenic and is the main target of the alloimmune response, immune monitoring in VCA essentially relies on visual inspection and pathological examination of for-causes and protocol skin biopsies. Light microscopical and immunohistochemical analyses enable us to identify skin lesions that are characteristic, but not specific, of allograft rejection. Complementary approaches of immunological assessment may assist in reinforcing the diagnosis of rejection and preventing over-immunosuppression or under-immunosuppression. Such approaches can inform either on the patient's global immune status or more specifically on the B-cell-mediated or T-cell-mediated immune responses against donor antigens.

SUMMARY

Strategies that integrate both the current 'gold standards' of monitoring in VCA and a complementary multilayer immunological assessment are likely to provide the highest precision for the personalized determination of the recipients' immunological status. The objective is a tailored adaptation of immunosuppressive treatment.

Rituximab and Monitoring Strategies for Late Antibody-Mediated Rejection After Kidney Transplantation

Background

There is limited information on treatment strategies and monitoring strategies for late antibody-mediated rejection (ABMR) after kidney transplantation.

Methods

In this observational and nonrandomized study, we compared 78 patients diagnosed with late ABMR (>3 months after transplant) who were treated with standard of care steroids/IVIG (n = 38) ± rituximab (n = 40) at our center between March 1, 2013 and December 31, 2016. All patients had follow-up biopsy and donor-specific antibodies (DSA) monitoring within 3 to 12 weeks.

Results

Patients had biopsy 7.3 ± 7 years after transplant and were followed for 15.9 ± 9.6 months after ABMR was diagnosed. Both treatment strategies were associated with a significant decline in DSA, microvascular inflammation (peritubular capillaritis + glomerulitis), and C4d Banff scores. In univariate regression analyses, rituximab, estimated glomerular filtration rate (eGFR), Banff i, t, v, chronicity (interstitial fibrosis + tubular atrophy + fibrous intimal thickening + allograft glomerulopathy) scores on the first biopsy, and eGFR and Banff v score on follow-up biopsy were associated with graft loss. Multivariate analyses retained only rituximab (hazard ratio, 0.23; 95% confidence interval, 0.06-0.84; P = 0.03) and eGFR at follow-up biopsy (0.84; 95% confidence interval, 0.76-0.92; P < 0.001) as significant predictors of graft loss. Kaplan-Meier analyses demonstrated that the benefit associated with rituximab was apparent after 1 year (15% vs 32% graft loss, P = 0.02).

Conclusion

Treatment of late ABMR with steroids/IVIG ± rituximab was effective in reducing DSA and microcirculation inflammation. The addition of rituximab was associated with better graft survival. Follow-up biopsies could be considered in the management of acute rejection to monitor the effect of therapy. Randomized studies on the best therapeutic options for ABMR are needed.

Diffuse Extent of Peritubular Capillaritis in Late Antibody-Mediated Rejection: Associations With Levels of Donor-Specific Antibodies and Chronic Allograft Injury

BACKGROUND

Recently, diffuse peritubular capillaritis (ptc) has been suggested to independently predict chronic transplant injury and loss, and although the ptc score is a diagnostic criterion for antibody-mediated rejection, the utility of diffuse ptc is under debate.

METHODS

We evaluated the diagnostic value of ptc characteristics in this cross-sectional study including 85 biopsies of patients with donor-specific antibodies (DSA). Biopsies were reevaluated for the extent (diffuse vs focal), score and leukocytic composition in relation to DSA binding strength (mean fluorescence intensity [MFI]_max). Chronic allograft injury (transplant chronic glomerulopathy [cg] or chronic lesion score CLS]) were associated with ptc features.

RESULTS

Peritubular capillaritis was detected in 50% (76% mononuclear ptc). Peritubular capillaritis scores 1, 2, and 3 were present in 36%, 55%, and 9%, and focal or diffuse ptc in 36% or 64%. Diffuse ptc was associated with DSA MFI_max (median: 4407 vs 2419 [focal ptc; P = 0.04] or 1946 [no ptc; P = 0.004]), cg (58% vs no ptc 24% [P = 0.02]), and higher CLS (mean: 6.81 vs 4.67 [focal ptc, P = 0.01] or 5.18 [no ptc, P = 0.001]), respectively. The association of ptc score of 2 or greater with cg was slightly better than with diffuse ptc. Diffuse ptc and ptc score of 2 or greater remained independently related to cg after adjusting for DSA_MFI_max, C4d, or previous rejection episodes, however lost their independent relation after adjusting for total microcirculation scores. Diffuse ptc was the only ptc characteristic independently related to CLS.

CONCLUSIONS

Our results emphasize the clinical relevance of reporting diffuse ptc, which may relate to DSA binding strength and potentially to chronic graft injury.

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.

Reason and Resolution of High Negative Control Beads in Solid-Phase Immunoassay

OBJECTIVES

The Luminex technology is the most sensitive diagnostic method for HLA antibody detection and identification. However, the interpretation of immunoassays is commonly affected by the artifact, and non-specific background. Sera from some patients show high negative control bead (NC) value, which makes assessing and interpretation of HLA antibodies difficult. In this study, we evaluated the effect of Adsorb Out reagent, dithiothreitol (DTT), and Ethylenediaminetetraacetic acid (EDTA) on the NC median fluorescence intensity value by comparing treated versus untreated patient sera. In addition, we wanted to identify whether kidney disease and administered medication influenced high NC median fluorescence intensity values by comparing patient versus control results.

MATERIALS AND METHODS

HLA antibody screening was performed on 3500 serum samples. Sera were analyzed using the standard protocol for Luminex antibody screening. Sera with high NC values were preincubated with Adsorb Out, DTT, and EDTA. Screening of these sera was then performed.

RESULTS

We found that 4% of samples showed high NC values. Adsorb Out, DTT, and EDTA decreased the NC values at 723.5 (299.25-1443) versus 85 (34-218; P < .001), at 723.5 (299.25-1443) versus 184 (106-597; P < .001), and at 723.5 (299.25-1443) versus 455 (131-1177; P = .004). These succeeded in bringing back NC values to normal range in 69.2%, 43%, and 30% of treated sera, respectively. In addition, the differences of corticoids, immunosuppressive, and heparin drugs between patients and controls were statistically significant (P < .001, < .001, and = .043). However, presence of kidney disease was not significant between these groups.

CONCLUSIONS

All pretreatments had an important effect in decreasing negative control values, with Adsorb Out having highest efficiency. Serum-specific components could contribute to high negative control bead median fluorescence intensity values. Further studies are needed to determine the adequate pretreatment of patient sera.

Evidence for CD16a-Mediated NK Cell Stimulation in Antibody-Mediated Kidney Transplant Rejection

BACKGROUND

Natural killer (NK) cells localize in the microcirculation in antibody-mediated rejection (AMR) and have been postulated to be activated by donor-specific anti-HLA antibodies triggering their CD16a Fc receptors. However, direct evidence for NK cell CD16a triggering in AMR is lacking. We hypothesized that CD16a-inducible NK cell-selective transcripts would be expressed in human AMR biopsies and would offer evidence for CD16a triggering.

METHODS

We stimulated human NK cells through CD16a in vitro, characterized CD16a-inducible transcripts, and studied their expression in human kidney transplant biopsies with AMR and in an extended human cell panel to determine their selectivity.

RESULTS

In NK cells, CD16a stimulation induced increased expression of 276 transcripts (FC > 2x, false discovery rate < 0.05), including IFNG, TNF, CSF2, chemokines, such as CCL3, CCL4, and XCL1, and modulators of NK cell effector functions (TNFRSF9, CRTAM, CD160). Examination in an extended human cell panel revealed that CD160 and XCL1 were likely to be selective for NK cells in AMR. In biopsies, 8 of the top 30 CD16a-inducible transcripts were highly associated with AMR (P < 5 × 10): CCL4, CD160, CCL3, XCL1, CRTAM, FCRL3, STARD4, TNFRSF9. Other NK cell transcripts (eg, GNLY) were increased in AMR but not CD16a-inducible, their presence in AMR probably reflecting NK cell localization.

CONCLUSIONS

The association of CD16a-inducible NK cell-selective transcripts CD160 and XCL1 with biopsies with AMR provides evidence for NK cell CD16a activation in AMR. This raises the possibility of other CD16a-triggered effects that are not necessarily transcriptional, including NK localization and cytotoxicity.

Bortezomib for refractory acute antibody-mediated rejection in kidney transplant recipients: A single-centre case series

AIM

Acute antibody-mediated rejection (ABMR) after kidney transplantation (KT) is associated with poor allograft survival. Current therapies for ABMR are able to deplete B-lymphocytes but do not target plasma cells. Bortezomib is a proteasome inhibitor that can eliminate plasma cells and has demonstrated utility in the treatment of ABMR.

METHODS

A retrospective study was carried out from 2010 to 2014, including all patients with ABMR refractory to conventional treatment who received bortezomib. Bortezomib (1.3 mg/m(2) ) was administered intravenously on days 1, 4, 8, and 11. Renal function, graft survival, follow-up biopsies, and donor-specific antibodies (DSA) were recorded.

RESULTS

We identified seven patients. Of these, high immunological risk was found in 6 of 7, preformed DSA were found in 5 of 7, flow cytometry crossmatch was positive in 4 of 7, and desensitization before KTx was provided in 6 of 7 patients. ABMR was diagnosed at a median of 90 days (8-167) post-KT. After bortezomib therapy, renal function improved or stabilized in 5 of 7 patients and progressively deteriorated in 2 of 7, leading to haemodialysis after 7 and 11 months, respectively. Follow-up kidney biopsies showed persistence of ABMR in 2 of 7, chronic active ABMR 3 of 7 and inactive chronic lesions in 2 of 7. DSA titres significantly decreased after treatment (P = 0.028). All patients experienced mild adverse events. After a follow-up of 22 ± 18 months, three grafts were lost (42%) and four remained functioning.

CONCLUSION

Bortezomib could be useful as an adjuvant therapy for ABMR refractory to conventional treatment with acceptable mid-term outcomes in these severe cases. More research is needed to develop strategies to better preserve graft function after refractory ABMR.

Current pathological perspectives on chronic rejection in renal allografts

Chronic rejection in renal transplantation clinically manifests as slow deterioration in allograft function and is a major contributor of late renal graft loss. Most cases of chronic rejection involve chronic antibody-mediated rejection (ABMR) triggered by the interaction of donor-specific alloantibodies with endothelial cells of the microcirculation. The evolution of the Banff classification involved a major revision of the ABMR criteria during the 2000s and led to the inclusion of detailed pathological characteristics of chronic ABMR in the 2013 Banff scheme, including microcirculation damage observed as newly formed basement membranes and arterial fibrous intimal proliferation. Inflammation of microvasculature including glomeruli and/or peritubular capillaries is also seen in substantial cases of chronic ABMR, defined as chronic active ABMR. Chronic active T cell-mediated rejection (TCMR) results from chronic T cell-mediated injury involving renal arteries but is less characterized under the current Banff classification, mainly due to the expanding histological criteria of chronic active ABMR. Characteristics shared by these two chronic rejection types can potentially cause diagnostic confusion. Hence, the diagnostic criteria or categories of chronic renal rejection require amendment of the current Banff classification. Assessment of rejection cases with molecular phenotyping advanced the mechanistic understanding of various dysfunctions in renal allograft, including ABMR and TCMR. Identification of disease-specific changes in gene expression by immunohistological studies, especially in chronic ABMR, has already been validated by several studies, warranting potential application to the pathological diagnostic process. This review provides an overview of current pathological perspectives on chronic rejection of renal allografts and future directions.

The effect of histopathologic and clinical features on allograft survival in renal transplant patients with antibody-mediated rejection

Background: Antibody-mediated rejection is a frequent cause of graft failure; however, prognostic indications of this complication have not been well defined. The aim of this study was to evaluate the association of histopathological and clinical features and to determine the effect of these findings on allograft survival in patients with AMR.

Methods: Fifty-two patients suffered from AMR (30 male; mean age 39 ± 11 years) were included in the study. Data were investigated retrospectively and graft survival was analyzed. All transplant biopsies were evaluated according to Banff 2009 classification.

Results: Of the 52 cases, 45 were transplanted from living-donors. Twenty-one patients were diagnosed in the first 3-months after transplantation. Graft survival was 65% at 12 months and 54% at 36 months. Mean serum creatinine at time of biopsy was 3.8 ± 3.6 mg/dL. Thirty-five of the 52 cases showed diffuse C4d positivity, 12 cases showed focal and 5 remained C4d negative. One of the patients died, 13 experienced graft loss and 38 survived with functioning grafts. Serum creatinine levels at time of biopsy were correlated with graft survival (p = .021: OR = 1.10: 95 % CI = 1.015–1.199). In terms of the impact of pathological findings; tubulitis (p=.007: OR = 2.62: 95 % CI = 1.301–5.276), intimal arteritis (p=.017: OR = 2.85: 95% CI = 1.205–6.744) and interstitial infiltration (p=.004: OR = 3.37: 95% CI = 1.465–7.752) were associated with graft survival.

Conclusions: Serum creatinine at time of biopsy, tubulitis, intimal arteritis and interstitial infiltration were significantly associated with graft survival. Antibody-mediated rejection is associated with reduced long-term graft survival.

Rapamycin Interferes With Postdepletion Regulatory T Cell Homeostasis and Enhances DSA Formation Corrected by CTLA4-Ig

Previously, we demonstrated that alemtuzumab induction with rapamycin as sole maintenance therapy is associated with an increased incidence of humoral rejection in human kidney transplant patients. To investigate the role of rapamycin in posttransplant humoral responses after T cell depletion, fully MHC mismatched hearts were transplanted into hCD52Tg mice, followed by alemtuzumab treatment with or without a short course of rapamycin. While untreated hCD52Tg recipients acutely rejected B6 hearts (n = 12), hCD52Tg recipients treated with alemtuzumab alone or in conjunction with rapamycin showed a lack of acute rejection (MST > 100). However, additional rapamycin showed a reduced beating quality over time and increased incidence of vasculopathy. Furthermore, rapamycin supplementation showed an increased serum donor-specific antibodies (DSA) level compared to alemtuzumab alone at postoperation days 50 and 100. Surprisingly, additional rapamycin treatment significantly reduced CD4(+) CD25(+) FoxP3(+) T reg cell numbers during treatment. On the contrary, ICOS(+) PD-1(+) CD4 follicular helper T cells in the lymph nodes were significantly increased. Interestingly, CTLA4-Ig supplementation in conjunction with rapamycin corrected rapamycin-induced accelerated posttransplant humoral response by directly modulating Tfh cells but not Treg cells. This suggests that rapamycin after T cell depletion could affect Treg cells leading to an increase of Tfh cells and DSA production that can be reversed by CTLA4-Ig.

Natural killer cells play a critical role in mediating inflammation and graft failure during antibody-mediated rejection of kidney allografts

While the incidence of antibody-mediated kidney graft rejection has increased, the key cellular and molecular participants underlying this graft injury remain unclear. Rejection of kidney allografts in mice lacking the chemokine receptor CCR5 is dependent on production of donor-specific antibody. Here we determine if cells expressing cytotoxic function contributed to antibody-mediated kidney allograft rejection in these recipients. Wild-type C57BL/6, B6.CCR5(-/-), and B6.CD8(-/-)/CCR5(-/-) mice were transplanted with complete MHC-mismatched A/J kidney grafts, and intragraft inflammatory components were followed to rejection. B6.CCR5(-/-) and B6.CD8(-/-)/CCR5(-/-) recipients rejected kidney allografts by day 35, whereas 65% of allografts in wild-type recipients survived past day 80 post-transplant. Rejected allografts in wild-type C57BL/6, B6.CCR5(-/-), and B6.CD8(-/-)/CCR5(-/-) recipients expressed high levels of VCAM-1 and MMP7 mRNA that was associated with high serum titers of donor-specific antibody. High levels of perforin and granzyme B mRNA expression peaked on day 6 post-transplant in allografts in all recipients, but were absent in isografts. Depletion of natural killer cells in B6.CD8(-/-)/CCR5(-/-) recipients reduced this expression to background levels and promoted the long-term survival of 40% of the kidney allografts. Thus, natural killer cells have a role in increased inflammation during antibody-mediated kidney allograft injury and in rejection of the grafts.

Acute Antibody-Mediated Rejection in Kidney Transplant Based on the 2013 Banff Criteria: Single-Center Experience in Uruguay

BACKGROUND

Acute antibody-mediated rejection (AMR) diagnosis criteria have changed in recent consensus of Banff, with current evidence of C4d-negative AMR. Our objective was to evaluate incidence of AMR in renal transplantation according to Banff 2013 criteria and to examine the histological features and outcome.

METHODS

This retrospective study involved all kidney transplants with histological diagnosis of acute rejection (AR) at our center between 2000 and 2014. All the biopsies with AR were re-assessed by a nephro-pathologist and classified by use of the Banff 2013 criteria.

RESULTS

Of 205 kidney transplants, biopsy-proven AR was diagnosed in 25 cases (12%). Re-assessing them according to Banff 2013 criteria, AMR was diagnosed in 17 (8.3%) and represented 68% of the confirmed rejections. AMR diagnosis was performed on day 23 ± 26, with median of 11 days. From the 17 cases, 7 had concomitant T-cell-mediated rejection. All cases presented endothelial edema and acute tubular necrosis. Glomerulitis was found in 12 cases and capillaritis in 14. In 3, associated thrombotic micro-angiopathy (TMA) was found. Intimal and transmural arteritis was evidenced in 5 and 1 patient. In 2, transplant glomerulopathy was present. Seven of the 10 biopsies with C4d staining in the peri-tubular capillaries were positive. Twelve cases received plasmapheresis, 6 received gamma-globulin, and 6 received rituximab. After administration of anti-AMR therapy, 16 cases recovered renal function, reaching a serum creatinine level of 1.5 ± 0.6 mg %. Graft survival at 1 year was lower in the AMR group versus patients without AMR (81.9% vs 98.9%, log-rank test, P < .001). Risk factors for AMR were re-transplant (30% vs 7%, P = .02), HLA-DR mismatch (1.06 ± 0.65 vs 0.7 ± 0.6, P = .03), panel-reactive antibody (28% ± 33 vs 6.2 ± 13, P = .00), and delayed graft function (82% vs 30%, P = .00).

CONCLUSIONS

Adapting the new Banff 2013 criteria increased the sensitivity of the diagnosis of ARM. Regarding our data, despite an adequate response to the therapy, it resulted in a worse graft survival by the first year of renal transplant.

Memory CD4 T Cells Induce Antibody-Mediated Rejection of Renal Allografts

Despite advances in immunosuppression, antibody-mediated rejection is a serious threat to allograft survival. Alloreactive memory helper T cells can induce potent alloantibody responses and often associate with poor graft outcome. Nevertheless, the ability of memory T cells to elicit well characterized manifestations of antibody-mediated rejection has not been tested. We investigated helper functions of memory CD4 T cells in a mouse model of renal transplantation. Whereas the majority of unsensitized C57Bl/6 recipients spontaneously accepted fully MHC-mismatched A/J renal allografts, recipients containing donor-reactive memory CD4 T cells rapidly lost allograft function. Increased serum creatinine levels, high serum titers of donor-specific alloantibody, minimal T cell infiltration, and intense C4d deposition in the grafts of sensitized recipients fulfilled all diagnostic criteria for acute renal antibody-mediated rejection in humans. IFNγ neutralization did not prevent the renal allograft rejection induced by memory helper T cells, and CD8 T cell depletion at the time of transplantation or depletion of both CD4 and CD8 T cells also did not prevent the renal allograft rejection induced by memory helper T cells starting at day 4 after transplantation. However, B cell depletion inhibited alloantibody generation and significantly extended allograft survival, indicating that donor-specific alloantibodies (not T cells) were the critical effector mechanism of renal allograft rejection induced by memory CD4 T cells. Our studies provide direct evidence that recipient T cell sensitization may result in antibody-mediated rejection of renal allografts and introduce a physiologically relevant animal model with which to investigate mechanisms of antibody-mediated rejection and novel therapeutic approaches for its prevention and treatment.

A candidate gene approach of the calcineurin pathway to identify variants associated with clinical outcomes in renal transplantation

AIM

To investigate the potential influence of variants in genes involved in the calcineurin pathway on the efficacy and toxicity of calcineurin inhibitors in renal transplantation.

MATERIALS & METHODS

Twenty-three polymorphisms in thirteen genes were tested in 381 renal transplant recipients receiving ciclosporin (n = 221) or tacrolimus (n = 160) and mycophenolate mofetil. Data were collected prospectively over the first year post-transplantation.

RESULTS

Multivariate survival analyses revealed no genetic associations with biopsy proven acute graft rejection and serious infections. Donor-recipient Cytomegalovirus mismatch was the only variable associated with serious infection.

CONCLUSION

This large exploratory study casts doubts on the potential interest of genetic biomarkers related to CNI pharmacodynamics but associations with other phenotypes in transplantation deserve further studies.

Successful treatment of severe acute antibody-mediated rejection of renal allografts with bortezomib--a report of two pediatric cases

aAMR in renal allografts is uncommon and remains a challenge as it is often refractory to treatment modalities. Aggressive therapy is essential to reverse the rejection as it results in renal allograft loss in approximately 27-40% of cases. There are anecdotal case reports of use of bortezomib, a proteasome inhibitor in the treatment of resistant AMR cases in solid organ transplant recipients; however, the experience is limited. We herein report successful reversal of resistant aAMR in two pediatric patients with bortezomib. Patients were initially treated with IV methylprednisolone pulse therapy with IVIG and PP three times weekly for a total of 10 treatments. After the standard therapy used at our institution persistence of DSA associated with graft dysfunction prompted the use of bortezomib to further treat the rejection. We did not have any neurologic side effects, but one patient did experience significant infections after bortezomib infusions requiring prolonged antimicrobial therapy. The long-term outcome of both children was excellent with preservation of normal renal function and persistent reduction in DSA titers.

The prognostic significance of glomerular infiltrating leukocytes during acute renal allograft rejection

Transplant glomerulitis, observed in T cell-mediated and antibody-mediated rejection, is histologically characterized by intracapillary mononuclear cell infiltration. However, the prognostic value of counting various glomerular inflammatory cells during rejection has not been elucidated, which is a key step for the introduction of novel biomarkers in the clinics. We immunophenotyped glomerulitis during episodes of acute rejection in order to investigate their predictive value for transplant outcomes. To do so, we included 57 transplant biopsies of 57 renal transplant recipients with biopsy-proven acute rejection with a median follow-up of 4.2 years. We determined average glomerular cell counts for T cells, B cells, Tregs, IL-17(+) cells, neutrophils and macrophages. Logistic and Cox regression models were used to investigate the association of glomerular inflammatory cells with response to therapy and graft failure on a population level. We used novel time-dependent ROC curve analyses to investigate the value of glomerular inflammatory cell infiltrates for the prediction of transplant outcomes, applicable to the individual patient. We identified three cell types that were responsible for glomerulitis during rejection: macrophages, T cells and neutrophils. By quantification of glomerular macrophages, an emerging cell type associated with antibody-mediated rejection, we were able to predict the progression towards death-censored graft failure within the first 500 days after the initial episode of rejection. With the use of novel time-dependent ROC analyses, we propose dynamic sensitivities, specificities, and positive and negative predictive values with their corresponding cut-off values for the average amount of glomerular macrophages, depending on what time after rejection death-censored graft failure needs prediction.

T-cell-mediated rejection of the kidney in the era of donor-specific antibodies: diagnostic challenges and clinical significance

PURPOSE OF REVIEW

Burgeoning literature on antibody-mediated rejection (ABMR) has led to a perception that T-cell-mediated rejection (TCMR) is no longer a significant problem. This premise needs to be carefully appraised.

RECENT FINDINGS

A review of the literature indicates that TCMR remains an independent-risk factor for graft loss. Importantly, it can occur as a sensitizing event that triggers ABMR, and adversely affects its outcome. Moreover, T cells are regularly present in lesions used to diagnose ABMR, and these lesions can also develop in the absence of donor-specific antibodies (DSA). Conversely, patients with DSA are at risk for mixed ABMR-TCMR, which is quite common in many studies, and may require a combined anti-T-cell and anti-B-cell strategy for the best outcome.

SUMMARY

T-cell-based clinical monitoring and therapy is still relevant for prophylaxis of both cellular and humoral rejection, treatment of steroid refractory TCMR, which occurs in up to 20% of patients, and optimization of clinical outcome in mixed TCMR-ABMR, which is more frequently encountered than generally appreciated, and still associated with unacceptably high rates of graft loss.

New insights in antibody-mediated rejection

PURPOSE OF REVIEW

In the present review, we aim to describe the state of knowledge concerning antibody-mediated rejection (ABMR) spectrum and diagnosis criteria before analyzing the present and future promising leads regarding ABMR prognosis markers and treatment.

RECENT FINDINGS

Recent studies regarding complement-binding donor-specific antibodies and the molecular approach highlighted the unmet need for stratification tools for prognosis and treatment inside ABMR disease.

SUMMARY

ABMR is the leading cause of kidney allograft failure. The recent expansion of its spectrum is related to the paradigm of a continuous process, leading insidiously to a chronic form of ABMR and to the progressive acknowledgement of new entities (such as vascular ABMR, subclinical ABMR, C4d-negative ABMR). Considering the global picture of ABMR, the Banff classification gradually refined the diagnosis criteria so that it now describes a clinically relevant and coherent entity. Nevertheless, if the diagnosis mainly relies on conventional assessment, such as histological findings and circulating donor-specific antibodies, these criteria face serious limitations in terms of stratification of patients at risk of graft loss inside ABMR disease. Recently, new promising tools have emerged in order to identify long-term outcomes at the time of the diagnosis of rejection. In this regard, donor-specific antibodies' complement-fixing ability and the molecular approach contributed significantly. Currently, however, no clinically relevant surrogate marker of treatment efficiency is currently available.

Recent advances in renal transplantation: antibody-mediated rejection takes center stage

Overlooked for decades, antibodies have taken center stage in renal transplantation and are now widely recognized as the first cause of allograft failure. Diagnosis of antibody-mediated rejection has considerably improved with identification of antibody-mediated lesions in graft biopsies and advances made in the detection of circulating donor-specific antibodies. Unfortunately, this progress has not yet translated into better outcomes for patients. Indeed, in the absence of a drug able to suppress antibody generation by plasma cells, available therapies can only slow down graft destruction. This review provides an overview of the current knowledge of antibody-mediated rejection and discusses future interesting research directions.

Combined induction therapy with rabbit antithymocyte globulin and rituximab in highly sensitized renal recipients

Compared to non-sensitized renal transplant recipients, patients with preformed alloantibodies are at greater risk of cellular and humoral rejection and premature graft failure. We explored the effects of adding B-cell depleting agent (rituximab) to standard rabbit anti-thymocyte globulin (rATG) induction regimen for patients with panel reactive antibody levels >50%. Following induction therapy, 14 recipients were given two doses of rituximab (375 mg/m(2)) within the first month post-transplantation. Their long-term outcomes were compared to a historical control group of 23 recipients who received rATG alone. Graft survival at 5 years was superior with combination therapy compared to induction therapy alone (92.9 versus 48.3%, respectively, p = 0.02). While 30% of the rATG alone group experienced cellular rejection and 26% humoral rejection, none of rituximab plus rATG renal transplant recipients group had rejection. Thus, addition of rituximab to rATG provided superior outcomes to rATG alone. This combination induction therapy should be considered for a high-risk population.

Reassessing the Significance of Intimal Arteritis in Kidney Transplant Biopsy Specimens

Intimal arteritis (the presence of v-lesions) in kidney transplant biopsy specimens is believed to have major prognostic and diagnostic significance. We assessed the relationship of v-lesions to prognosis in 703 indication biopsy specimens and used microarray-based molecular tests to re-examine the relationship of v-lesions to rejection. v-Lesions were noted in 49 specimens (7%) and were usually mild (v1). The presence of v-lesions had no effect on graft survival compared with the absence of v-lesions. Pathologists using current conventions almost always interpreted v-lesions as reflecting T cell-mediated rejection (TCMR), either pure or mixed with antibody-mediated rejection (ABMR). The molecular scores questioned the conventional diagnoses in 29 of 49 specimens (59%), including ten that were conventional TCMR with no molecular rejection and nine that were conventional TCMR mixed with pure ABMR molecularly. The presence of tubulointerstitial inflammation (i-t) meeting TCMR criteria allowed subclassification of v-lesion specimens into 21 i-t-v-lesion specimens and 28 isolated v-lesion specimens. Molecular TCMR scores were positive in 95% of i-t-v-lesion specimens but only 21% of isolated v-lesion specimens. Molecular ABMR scores were often positive in isolated v-lesion biopsies (46%). Time of biopsy after transplantation was critical for understanding isolated v-lesions: most early isolated v-lesion specimens had no molecular rejection and were DSA negative, whereas most isolated >1 year after transplantation had positive DSA and ABMR scores. Therefore, v-lesions in indication biopsy specimens do not affect prognosis and can reflect TCMR, ABMR, or no rejection. Time after transplantation, DSA, and accompanying inflammation provide probabilistic basis for interpreting v-lesions.

Differential modulation of donor-specific antibodies after B-cell depleting therapies to cure chronic antibody mediated rejection

BACKGROUND

Donor-specific antibodies (DSA) are considered as reliable biomarkers for antibody-mediated rejection (ABMR) diagnosis. However, it is unclear whether DSA monitoring is necessary and could predict graft outcome after antirejection treatment.

METHODS

We analyzed 28 non-sensitized kidney transplant patients with ABMR associated with de novo anti-human leukocyte antigen (HLA) DSA. Donor-specific antibody levels were measured by single antigen bead assays 12 months after antirejection therapy onset. Patients were placed in three groups according to their antirejection treatment: group I (n = 10), plasma exchange-Rituximab; group II (n = 8), Bortezomib; and group III (n = 10), optimization of maintenance immunosuppression. Half of the patients in group I demonstrated concomitant acute cellular rejection (ACR+).

RESULTS

De novo DSA were mainly anti-DQ (60%). Anti-class I and anti-DR DSA disappeared after treatment in group I and remained negative during follow-up, whereas anti-DQ DSA persisted without any modulation. In contrast, class I-II HLA-DSA mean fluorescence intensity remained unchanged in groups II and III.Graft loss was observed in 80% and 20% of patients from group I (ACR+) and group III, respectively. One year after the ABMR treatment, a 16-mL/min decline in estimated glomerular filtration rate was observed in patients from group I (ACR-) and group III. Group II showed better outcomes with a mean estimated glomerular filtration rate decline of 6.4 mL/min.

CONCLUSION

Modulation of DSA at and after treatment of ABMR did not correlate with graft outcome over a 12-month period.

Methods of analysis for peritubular capillaritis and glomerulitis in acute renal rejection: capillaritis in management of routine diagnosis

Glomerulitis and peritubular capillaritis have been recognized as important lesions in acute renal rejection (AR). We studied glomerulitis and peritubular capillaritis in AR by 2 methods and investigated associations with C4d, type/grade of AR, and allograft survival time. Glomerulitis was measured according to Banff scores (glomerulitis by Banff Method [gBM]) and by counting the number of intraglomerular inflammatory cells (glomerulitis by Quantitative Method [gQM]). Capillaritis was classified by the Banff scoring system (peritubular capillaritis by Banff Method [ptcBM]) and by counting the number of cells in peritubular capillaries in 10 high-power fields (hpf; peritubular capillaritis by Quantitative Method [ptcQM]). These quantitative analyses were performed in an attempt to improve our understanding of the role played by glomerulitis and capillaritis in AR. The g0 + g1 group (gBM) associated with negative C4d (P = .02). In peritubular capillaritis, a larger number of cells per 10 hpf in peritubular capillaries (ptcQM) were observed in positive C4d cases (P = .03). The group g2 + g3 (gBM) correlated with graft loss (P = .01). Peritubular capillaritis was not significantly related to graft survival time. Our study showed that the Banff scoring system is the best method to study glomerulitis and observed that the evaluation of capillaritis in routine biopsies is difficult and additional studies are required for a better understanding of its meaning in AR biopsy specimens of renal allografts.