High B‐cell activating factor is not associated with worse 3‐year graft outcome in blood group‐incompatible kidney transplantation with rituximab induction

B cells and their regulation by B‐cell activating factor BAFF are of growing interest in kidney transplantation (KTx). There is evidence that high serum (s) BAFF leads to increased allosensitization and impaired long‐term graft function. We prospectively investigated sBAFF, peripheral blood lymphocytes (PBL), and donor‐specific HLA antibodies (DSA) in patients after ABOi with B‐cell depleting rituximab induction treatment and compared them to a group of blood group‐compatible (ABOc) living donor kidney recipients. Twelve patients after ABOi and 18 after ABOc were included. After rituximab treatment prior to ABOi, B cells remained significantly lower 1 year after KTx (1.2% (0.0–17.8) compared to ABOc of 8.6% (2.8–35.0), p = 0.0004, and also BAFF‐R expression was significantly lower in ABOi (p < 0.006). sBAFF remained elevated 1 year post‐Tx compared to ABOc (3615 ± 1800 vs. 1394 ± 493 pg/mL, p < 0.004). Kidney function was not significantly different between both groups after 1, 2, and 3 years. The use of rituximab in ABOi together with maintenance immunosuppression leads to significant elevation of sBAFF and lowering of B‐cell numbers for more than 1 year, and this does not correlate with worse 3‐year graft outcome.     

The therapeutic challenge of late antibody‐mediated kidney allograft rejection

Late antibody‐mediated rejection (ABMR) is a cardinal cause of kidney allograft failure, manifesting as a continuous and, in contrast with early rejection, often clinically silent alloimmune process. While significant progress has been made towards an improved understanding of its molecular mechanisms and the definition of diagnostic criteria, there is still no approved effective treatment. In recent small randomized controlled trials, therapeutic strategies with promising results in observational studies, such as proteasome inhibitor bortezomib, anti‐C5 antibody eculizumab, or high dose intravenous immunoglobulin plus rituximab, had no significant impact in late and/or chronic ABMR. Such disappointing results reinforce a need of new innovative treatment strategies. Potential candidates may be the interference with interleukin‐6 to modulate B cell alloimmunity, or innovative compounds that specifically target antibody‐producing plasma cells, such as antibodies against CD38. Given the phenotypic heterogeneity of ABMR, the design of adequate systematic trials to assess the safety and efficiency of such therapies, however, is challenging. Several trials are currently being conducted, and new developments will hopefully provide us with effective ways to counteract the deleterious impact of antibody‐mediated graft injury. Meanwhile, the weight of evidence would suggest that, when approaching using existing treatments for established antibody‐mediated rejection, “less may be more”.     

Validation of genetic variants associated with early acute rejection in kidney allograft transplantation

Numerous reports have identified genetic variants associated with kidney transplant outcome, but only a few have been validated in subsequent studies. We analyzed the association of 21 previously reported genetic variants associated with acute rejection (AR), in an effort to validate these associations in our kidney transplant population. All recipients (n = 585) received Ab induction, rapid discontinuation of prednisone, and calcineurin inhibitors with either mycophenolate mofetil or sirolimus. Both univariate analysis and logistic regression were used for determining the association between the genotypes and AR. Univariate analysis detected one significant single-nucleotide polymorphism (p = 0.03), rs1801133, within the methylenetetrahydrofolate reductase (MTHFR) gene associated with AR. Logistic regression analysis identified two variants associated with AR, the 32-bp deletion within chemokine (C-C motif) receptor 5 gene (rs333) and the p.222A/V variant (rs1801133) within the MTHFR gene. Although our analysis utilized a much larger cohort than used in previous reports, we were only able to detect an association with two of these variants. The lack of validation for the other 19 variants may be due to the small effect size, or that, they are not associated with AR. These results stress the need for larger cohorts for both future studies as well as for validation studies.     

A case of allograft dysfunction with antibody-mediated rejection developing 13 yr after kidney transplantation

Abstract:  Antibody-mediated rejection is an important cause of chronic allograft dysfunction. We report a case of chronic antibody-mediated rejection 13 yr after transplantation. This patient is a 19-yr-old man who had renal insufficiency since infancy because of bilateral polycystic kidneys. Peritoneal dialysis was started when he was four yr old and he received a renal allograft from his mother at the age of six yr. Donor and recipient were ABO compatible and immunosuppressive treatment was started with cyclosporine, mizoribine, and methylprednisolone. No acute rejection was experienced and histological acute rejection was not proven on any subsequent protocol biopsies. Ten yr after transplantation, a protocol biopsy revealed moderate chronic allograft nephropathy and severe cyclosporine-associated arteriolopathy. His allograft function was preserved at this time and the cyclosporine dose was tapered to 125 mg/d. His renal function gradually deteriorated starting 12 yr after transplantation. Although mizoribine was changed to mycophenolate mofetil, he required dialysis one yr later. A diagnosis of antibody-mediated rejection was made based upon the renal biopsy findings (including C4d staining) and circulating anti-human leukocyte antigen (HLA) antibody levels (12 yr after transplantation). We conclude that it is necessary to pay attention to antibody-mediated rejection, even in allograft cases with good function for over 10 yr and no risk factors for the development of de novo anti-HLA antibodies.     

Natural killer cell infiltration is discriminative for antibody-mediated rejection and predicts outcome after kidney transplantation

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大鼠异体肢体移植术后急性排斥反应阶段血管内皮细胞ICAM-1表达的动态变化

目的 研究大鼠异体肢体移植术后急性排斥反应阶段,移植肢体血管内皮细胞细胞间黏附分子-1(intercellular adhesion molecule-1,ICAM-1)动态变化及环孢素A(cyclosporine A,CsA)抗免疫排斥的作用.方法 建立大鼠肢体移植动物模型,随机分为对照组(Wistar大鼠→Wistar大鼠)、排斥组(SD大鼠→ Wistar大鼠)和CsA治疗组(SD大鼠→Wistar大鼠),术后1、4、7 d获取移植肢体股动脉行病理学观察,采用免疫组化法检测移植肢体血管ICAM-1表达的变化.结果 对照组供体移植肢体股动脉血管内皮细胞仅出现轻微肿胀与ICAM-1表达微弱;排斥组血管内皮细胞肿胀明显,淋巴细胞大量浸润,ICAM-1的表达强度和数量明显增加;CsA治疗组移植肢体血管内皮细胞仅有少量淋巴细胞浸润,ICAM-1表达较弱.结论 大鼠异体肢体移植术后急性排斥反应阶段,血管内皮细胞ICAM-1表达水平与排斥反应的发生和发展有关,CsA可降低移植肢体血管内皮细胞ICAM-1表达,抑制复合组织移植术后急性排斥反应.     

Evidence of allograft related transplantation antigen binding cells for detection of cardiac allograft rejection—Preliminary report

Zusammenfassung In 8 heart transplant recipients in follow-up checks we have evaluated the binding of transplantation antigen loaded methacrylate-carrier to peripheral mononuclear cells (rosette technique). All patients were treated with a triple-drug regimen for immunosuppression, consisting of steroids, azathioprine and cyclosporine A. The increase of the number of these antigen binding cells over a limit value of 30 RFC/10³ MNC is a reliable sign of a beginning immune reaction against the graft. The evidence is given by comparing the results with these of situation in endomyocardial biopsies (EMB). The test is predictive 3 to 6 days before infiltrating cells are visible in biopsies and donor independent (use of antigen mixture from cadaver spleens). Zusammenfassung In Verlaufsuntersuchungen an 8 herztransplantierten Patienten wurde die Bindung mononukle?rer Zellen an transplantationsantigenbeladene Methakrylattr?ger (Rosettentechnik) untersucht. Alle Patienten erhielten eine standardisierte Basisimmunsuppression (Triple-Drug), bestehend aus Steroiden, Azathioprin und Cyclosporin A. Ein Anstieg antigenbindender Zellen über einen Grenzwert von 30 RFC/10³ MNC signalisiert eine beginnende Anti-Transplantatimmunreaktion. Der klinische Nachweis erfolgte stets mittels Endokardbiopsie. Der Test ist pr?diktiv (3 bis 6 Tage vor einer positiven Biopsie) und spenderunabh?ngig (Benutzung eines Antigengemisches aus humanen Milzen).

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New insights on innate B‐cell immunity in transplantation

Innate B cells and natural antibodies (Nabs) have been extensively studied in normal physiological conditions as well as in several diseases. However, their significance in the context of ABO‐compatible solid organ transplantation is only emerging. This review summarizes recent studies exploring these often neglected innate immune elements in situations related to sensitization and clinical graft rejection. A focus is placed on class‐switched IgG Nabs that develop amidst inflammation, rather than IgM Nabs abundant at the steady state, as new evidence point to their implication in serum reactivity to HLA and kidney graft failure. The involvement of innate B cells in the pathophysiology of CAV is also presented. Lastly, we discuss key questions that need answering to understand whether and how innate B‐cell immunity contributes to the outcome of solid organ transplantation.     

Impact of pretransplant donor‐specific antibodies on kidney allograft recipients with negative flow cytometry cross‐matches

The Luminex test can detect low levels of donor‐specific antibody (DSA) that cannot be detected by flow‐cytometric cross‐matching (FCXM) in kidney transplantation (KT). This study evaluated the impact of DSA on clinical outcomes in KT recipients negative on FCXM. Of 575 consecutive patients who underwent living donor KT between January 2013 and July 2016, 494 (85.9%) were DSA‐negative and 81 (14.1%) were DSA‐positive. Although rates of acute cellular rejection (ACR) at 1 year were similar in the 2 groups (P = .54), the incidence of antibody‐mediated rejection (ABMR) was significantly higher in the DSA‐positive group (P < .01). There was no statistically significant association between rejection‐free graft survival (RFGS) rates and pretransplant class I DSA. However, evaluation of pretransplant class II DSA showed that RFGS rates were significantly lower in patients with mean fluorescence intensity (MFI) >3000 than in patients with DSA‐negative (P < .01). On multivariate analyses, class II DSA MFI ≥5000 was a significant risk factor for acute rejection (hazard ratio, 7.48; P < .01). These findings suggested that pretransplant DSA alone did not affect graft survival in KT recipients without desensitization. However, class II DSA MFI >5000 was an independent predictor of acute rejection in DSA‐positive patients.     

Prevalence and immunohistochemical findings of subclinical kidney allograft rejection and its association with graft outcome

Subclinical acute rejection (SAR) occurs in about 30% of stable renal transplant patients and may be a risk factor for a poor allograft outcome. In the present study, the prevalence and clinical features of subclinical rejection, and the expression of immune activation markers in surveillance graft biopsies were assessed and correlated with late graft outcomes. Protocol biopsies were obtained at 2 and 12 months post-transplant in 32 and 26 patients, respectively, with stable renal function. The Banff 1997 criteria were used for histological diagnosis. Graft function and survival and proteinuria were assessed during the 36 months of follow-up. Immunohistochemical evaluation of cell subpopulations and immunoactivation markers were performed on protocol biopsies. The prevalence of SAR at 2 months and of chronic allograft nephropathy (CAN) at 12 months in representative biopsies was 55 and 50%, respectively. Patients with SAR presented mononuclear cell infiltration with an increased expression of CD3, CD4, CD68, IL-2R and granzyme B. Kidney graft function was significantly worse in patients with SAR at 2 months who had chronic rejection on biopsy at 12 months, but SAR was not associated with a worse graft function, greater proteinuria or a lower graft survival in 3 yr of follow-up. In conclusion, we found an elevated prevalence of SAR at 2 months after transplantation with an increased expression of activation markers. Although an association of SAR with poor graft outcome was not observed, our results suggest that SAR is an immunologically active process and underscore the importance of protocol biopsies in the surveillance of transplanted kidneys.     

Association of four DNA polymorphisms with acute rejection after kidney transplantation

Renal transplant outcomes exhibit large inter-individual variability, possibly on account of genetic variation in immune-response mediators and genes influencing the pharmacodynamics/pharmacokinetics of immunosuppressants. We examined 21 polymorphisms from 10 genes in 237 de novo renal transplant recipients participating in an open-label, multicenter study [Cyclosporine Avoidance Eliminates Serious Adverse Renal-toxicity (CAESAR)] investigating renal function and biopsy-proven acute rejection (BPAR) with different cyclosporine A regimens and mycophenolate mofetil. Genes were selected for their immune response and pharmacodynamic/pharmacokinetic relevance and were tested for association with BPAR. Four polymorphisms were significantly associated with BPAR. The ABCB1 2677T allele tripled the odds of developing BPAR (OR: 3.16, 95% CI [1.50–6.67]; P  =   0.003), as did the presence of at least one IMPDH2 3757C allele (OR: 3.39, 95% CI [1.42–8.09]; P  =   0.006). BPAR was almost fivefold more likely in patients homozygous for IL-10 -592A (OR: 4.71, 95% CI [1.52–14.55]; P  =   0.007) and twice as likely in patients with at least one A allele of TNF-α G-308A (OR: 2.18, 95% CI [1.08–4.41]; P  =   0.029). There were no statistically significant interactions between polymorphisms, or the different treatment regimens. Variation in genes of immune response and pharmacodynamic/pharmacokinetic relevance may be important in understanding acute rejection after renal transplant.     

B‐cell regulation and its application to transplantation

There has been increasing interest in the role played by B cells and their associated antibody in the immune response to an allograft, driven by the need to undertake antibody‐incompatible transplantation and evidence suggesting that B cells play a role in acute T‐cell‐mediated rejection and in acute and chronic antibody‐mediated rejection. This review focuses on the molecular events, both activating and inhibitory, which control B‐cell activation, and considers how this information might inform therapeutic strategies. Potential targets include the BAFF (B‐cell‐activating factor belonging to the tumour necrosis factor family) and CD40‐CD40L pathways and inhibitory molecules, such as CD22 and FcγRIIB. B cells can also play an immunomodulatory role via interleukin (IL)10 production and may contribute to transplant tolerance. The expansion of allograft‐specific IL10‐producing B cells may be an additional therapeutic goal. Thus, the treatment paradigm required in transplantation has shifted from that of simple B‐cell depletion, to that of a more subtle, differential manipulation of different B‐cell subsets.     

Immunophenotypic profile and clinical outcome of monoclonal B‐cell lymphocytosis in kidney transplantation

Monoclonal B‐cell lymphocytosis (MBL) is a lymphoproliferative disorder characterized by clonal expansion of a B‐cell population in peripheral blood of otherwise healthy subjects. MBL is divided into CLL (chronic lymphocytic leukemia)‐like, atypical CLL‐like and non‐CLL MBL. The aim of this study was to evaluate immunophenotypic characteristics and clinical outcomes of MBL in kidney transplant (KT) recipients. We retrospectively evaluated 593 kidney transplant (KT) recipients in follow‐up at our center. Among them, 157 patients underwent peripheral blood flow cytometry for different clinical indications. A 6‐color panel flow cytometry was used to diagnose MBL. This condition was detected in 5 of 157 KT recipients. Immunophenotypic characterization of MBL showed four cases of non‐CLL MBL and one case of CLL‐like MBL. At presentation, median age was 65 years (range 61‐73). After a median follow‐up of 3.1 years (95%CI; 1.1‐5) from diagnosis, patients did not progress either to CLL or to lymphoma. The disorder did not increase the risk of malignancy, severe infections, graft loss and mortality among our KT recipients. Surprisingly, all cases were also affected by concomitant monoclonal gammopathy of undetermined significance, which did not progress to multiple myeloma during follow‐up. In conclusion, our data suggest that MBL is an age‐related disorder, with non‐CLL MBL being the most common subtype among KT recipients.     

A case of plasma cell-rich acute rejection 18 months after kidney transplantation successfully treated with steroid pulse therapy

Abstract:  A 45-yr-old Japanese male underwent living-related kidney transplantation in August 2005, and immunosuppression consisted of tacrolimus, mycophenolate mofetil, methylprednisolone, basiliximab, and rituximab 200 mg. Allograft function was good, and the protocol biopsy post-transplant day 11 showed no evidence of rejection. The serum creatinine (s-Cr) level was maintained at the 1.2 mg/dL for 18 months. On February 2007, the patient's s-Cr level had increased to 2.03 mg/dL, and an episode biopsy was performed. The biopsy specimen demonstrated moderate to severe tubulitis and moderate interstitial infiltration of plasma cells and lymphocytes. The inflammatory cell infiltrate consisted of >30% plasma cells. The histopathological findings were consistent with plasma cell-rich acute rejection (PCAR). The PCAR was treated by steroid pulse therapy, and his s-Cr level decreased to 1.58 mg/dL. A biopsy three months after the steroid pulse therapy showed no evidence of rejection. The patient's allograft function is currently stable, and s-Cr level is 1.7 mg/dL. This is a case of PACR, that was successfully treated with steroid pulse therapy alone.     

Anti‐IL‐2R blockers comparing with polyclonal antibodies: Higher risk of rejection without negative mid‐term outcomes after ABO‐incompatible kidney transplantation

There is no recommendation regarding the type of induction therapy to use in ABO‐incompatible (ABOi) kidney transplantation. The aim of this retrospective study was to compare the outcome of ABOi living donor kidney transplant (LDKT) recipients who received either polyclonal antibodies or anti‐interleukin‐2 receptor (IL‐2R) blockers as an induction agent. All ABOi HLA‐compatible patients that received a LDKT between 03/11 and 03/18 in three French transplantation center (Paris Saint‐Louis, Paris Necker, and Toulouse) were included in the study. Fifty‐eight patients were given polyclonal antibodies and 39 patients received anti‐IL‐2R blockers. We identified by a Cox proportional hazard model the use of polyclonal antibodies as a protective factor against acute rejection (HR = 0.4, 95%CI [0‐0.9], P < .05). However, pathological findings on protocol biopsies at 1 year were similar in both groups, as were patient and graft survivals, renal function, and complications. We conclude that the acute rejection rate was significantly higher in patients given anti‐IL‐2R blockers compared to polyclonal antibodies. However, in our series, there was no negative impact on mid‐term outcome.