Desensitization in HLA-incompatible kidney recipients and survival

Incompatible kidney transplantation: a brief overview of the past, present and future

Live kidney donor transplantation across immunological barriers, either blood group or positive crossmatch [ABO- and human leucocyte antigens (HLA)-incompatible kidney transplantation, respectively], is now practised widely across many transplant centres. This provides transplantation opportunities to patients that hitherto would have been deemed contra-indicated and would subsequently have waited indefinitely for a suitably matched kidney. Protocols have evolved with time as experience has grown and now a variety of desensitization strategies are currently practised to overcome such immunological barriers. In addition, desensitization protocols are complemented by kidney paired donation exchange schemes and therefore incompatible patients now have strategies to either confront or bypass immunological barriers, respectively. As the field expands it is clear that non-transplant clinicians will be exposed to incompatible kidney transplant recipients outside of experienced centres. It is therefore timely to review the evolution of practice that have led to current desensitization modalities, contrast protocols and outcomes of current regimens and speculate on future direction of incompatible kidney transplantation.

Epidemiology, risk factors, and outcomes of Clostridium difficile infection in kidney transplant recipients

BACKGROUND

We sought to describe the epidemiology and risk factors for Clostridium difficile infection (CDI) among kidney transplant recipients (KTR) between 1 January 2008 and 31 December 2010.

METHODS

A single-institution retrospective study was conducted among all adult KTR with CDI, defined as a positive test for C. difficile by a cell cytotoxic assay for C. difficile toxin A or B or polymerase chain reaction test for toxigenic C. difficile.

RESULTS

Among 603 kidney transplants performed between 1 January 2008 and 31 December 2010, 37 (6.1%) patients developed CDI: 12 (of 128; 9.4%) high-risk (blood group incompatible and/or anti-human leukocyte antigen donor-specific antibodies) vs. 25 (of 475; 5.3%, P = 0.08) standard-risk patients. The overall rate of CDI increased from 3.7% in 2008 to 9.4% in 2010 (P = 0.05). The median time to CDI diagnosis was 9 days, with 27 (73.0%) patients developing CDI within the first 30 days after their transplant, and 14 (51.8%) developing CDI within 7 days. A case-control analysis of 37 CDI cases and 74 matched controls demonstrated the following predictors for CDI among KTR: vancomycin-resistant Enterococcus colonization before transplant (odds ratio [OR]: 3.6, P = 0.03), receipt of an organ from Centers for Disease Control high-risk donor (OR: 5.9, P = 0.006), and administration of high-risk antibiotics within 30 days post transplant (OR: 6.6, P = 0.001).

CONCLUSIONS

CDI remains a common early complication in KTR, with rates steadily increasing during the study period. Host and transplant-related factors and exposure to antibiotics appeared to significantly impact the risk for CDI among KTR.

Solid phase detection of C4d-fixing HLA antibodies to predict rejection in high immunological risk kidney transplant recipients

Protocols for recipient desensitization may allow for successful kidney transplantation across major immunological barriers. Desensitized recipients, however, still face a considerable risk of antibody-mediated rejection (AMR), which underscores the need for risk stratification tools to individually tailor treatment. Here, we investigated whether solid phase detection of complement-fixing donor-specific antibodies (DSA) has the potential to improve AMR prediction in high-risk transplants. The study included 68 sensitized recipients of deceased donor kidney allografts who underwent peritransplant immunoadsorption for alloantibody depletion (median cytotoxic panel reactivity: 73%; crossmatch conversion: n = 21). Pre and post-transplant sera were subjected to detection of DSA-triggered C4d deposition ([C4d]DSA) applying single-antigen bead (SAB) technology. While standard crossmatch and [IgG]SAB testing failed to predict outcomes in our desensitized patients, detection of preformed [C4d]DSA (n = 44) was tightly associated with C4d-positive AMR [36% vs. 8%, P = 0.01; binary logistic regression: odds ratio: 10.1 (95% confidence interval: 1.6-64.2), P = 0.01]. Moreover, long-term death-censored graft survival tended to be worse among [C4d]DSA-positive recipients (P = 0.07). There were no associations with C4d-negative AMR or cellular rejection. [C4d]DSA detected 6 months post-transplantation were not related to clinical outcomes. Our data suggest that pretransplant SAB-based detection of complement-fixing DSA may be a valuable tool for risk stratification.

Human leukocyte antigen antibody incompatible renal transplantation

Anti-human leukocyte antigen (HLA) antibodies are recognized as an important problem in organ transplant recipients. This is because antibodies formed against a graft months or years after implantations are the major cause of late allograft failure, and also because protocols allow the transplantation of some grafts across pre-formed HLA antibodies. Advances in our understanding of anti-HLA antibody- mediated rejection (AMR) have occurred because of a better understanding of the histological findings during AMR; more sensitive and specific methods to measure anti-HLA antibodies; and through clinical investigation of patients transplanted across an HLA barrier. Despite advances in therapy and investigation, AMR remains a major problem and treatment protocols often fail to treat it successfully. This review aims to describe the issues in each of these areas and to suggest how clinicians may be able to improve the management of patients with anti-HLA antibodies.

Lack of effect in desensitization with intravenous immunoglobulin and rituximab in highly sensitized patients

BACKGROUND

We conducted a prospective cohort study in highly sensitized kidney transplant candidates with a calculated panel reactive antibody (cPRA) greater than 50% and on the deceased-donor waiting list for more than 5 years to investigate the effects of intravenous immunoglobulin (IVIG) and rituximab treatment.

METHODS

Desensitization protocol included two doses of IVIG (2 g/kg, max 120 g each dose) and a single dose of rituximab (375 mg/m(2)). Patients were followed up monthly by Luminex single antigen beads. Whole blood gene expression profiles were studied by Affymetrix Human 1.0 ST GeneChips before and after treatment.

RESULTS

Forty patients were eligible for desensitization treatment. Thirteen of these patients agreed to participate, and 11 completed the treatment. After a mean follow-up of 334 ± 82 days, two desensitized patients (18%) received a kidney transplant compared with 14 patients (52%) in the nondesensitized group. Comparing with 14 patients who received transplants without any desensitization treatment, desensitized patients showed higher class I (99% vs. 80%) and class II (98% vs. 69%) cPRA levels and more unacceptable antigens (32 vs. 8). Desensitization treatment did not lead to any significant reduction in patients' class I and II cPRA levels and any change in the mean number of unacceptable antigens or their mean fluorescence intensity values. Whole blood gene expression analysis by microarrays demonstrated down-regulation of immunoglobulin and B-cell-associated transcripts after treatment.

CONCLUSION

These results suggested that pretransplant desensitization with IVIG and rituximab was not successful in highly sensitized kidney transplant candidates with cPRA levels higher than 90%.

Preliminary results of the first human uterus transplantation from a multiorgan donor

OBJECTIVE

To describe the first-year results of the first human uterus transplantation case from a multiorgan donor.

DESIGN

Case study.

SETTING

University hospital.

PATIENT(S)

A 21-year-old woman with complete müllerian agenesis who had been previously operated on for vaginal reconstruction.

INTERVENTION(S)

Uterus transplantation procedure consisting of orthotopic replacement and fixation of the retrieved uterus, revascularization, end to site anastomoses of bilateral hypogastric arteries and veins to bilateral external iliac arteries and veins was performed.

MAIN OUTCOME MEASURE(S)

Resumption of menstrual cycles.

RESULT(S)

The patient had menarche 20 days after transplant surgery. She has had 12 menstrual cycles since the operation.

CONCLUSION(S)

We have described the longest-lived transplanted human uterus to date with acquirement of menstrual cycles.

Effect of red cell transfusions on future kidney transplantation

Red cell transfusions, erythropoiesis-stimulating agents (ESAs), and intravenous iron therapy all have a place in the treatment of anemia associated with CKD. Their relative merits and uses are subject to many clinical and nonclinical factors. New concerns associated with the use of ESA therapy make it likely that the use of blood transfusions will increase, refueling previous debates about their associated risks. Data on whether red cell transfusions increase sensitization to HLA antigens, rendering subsequent transplantation more problematic, are mainly derived from older literature. Older data suggested that women were more at risk of HLA sensitization than men, particularly those with previous multiple pregnancies, although recent U.S. Renal Data System data have challenged this. HLA sensitization prolongs the waiting time for transplantation and reduces graft survival. Leukocyte depletion of red cells does not appear to reduce the risk of HLA sensitization. This review summarizes much of the data on these issues, as well as highlighting the need for further research on the potential risks for blood transfusion in patients with CKD.

Prevention of antibody-mediated kidney transplant rejection

There is increasing evidence that antibody-mediated rejection is the major cause of late kidney graft failure. Prevention of antibody-mediated allograft damage has therefore become an important issue in kidney transplantation. Such prevention starts already before transplantation with the avoidance of sensitizing events. When a patient is already sensitized, precise characterization of alloantibodies and exact HLA typing of the donor at the time of transplantation are mandatory. To ensure timely and successful transplantation of highly sensitized patients, desensitization, and inclusion in special programs such as the Eurotransplant Acceptable Mismatch Program should be considered. After transplantation, close monitoring of kidney function, testing for the de novo development or changing characteristics of alloantibodies, and attention to non-adherence to immunosuppression is obligatory. In the current overview, we discuss the currently available measures for the prevention of antibody-mediated kidney graft rejection.

HLA-haploidentical bone marrow transplantation with posttransplant cyclophosphamide expands the donor pool for patients with sickle cell disease

Allogeneic marrow transplantation can cure sickle cell disease; however, HLA-matched donors are difficult to find, and the toxicities of myeloablative conditioning are prohibitive for most adults with this disease. We developed a nonmyeloablative bone marrow transplantation platform using related, including HLA-haploidentical, donors for patients with sickle cell disease. The regimen consisted of antithymocyte globulin, fludarabine, cyclophosphamide, and total body irradiation, and graft-versus-host disease prophylaxis with posttransplantation high-dose cyclophosphamide, mycophenolate mofetil, and tacrolimus or sirolimus. After screening 19 patients, we transplanted 17, 14 from HLA-haploidentical and 3 from HLA-matched related donors. Eleven patients engrafted durably. With a median follow-up of 711 days (minimal follow up 224 days), 10 patients are asymptomatic, and 6 patients are off immunosupression. Only 1 patient developed skin-only acute graft-versus-host disease that resolved without any therapy; no mortality was seen. Nonmyeloablative conditioning with posttransplantation high-dose cyclophosphamide expands the donor pool, making marrow transplantation feasible for most patients with sickle cell disease, and is associated with a low risk of complications, even with haploidentical related donors. Graft failure, 43% in haploidentical pairs, remains a major obstacle but may be acceptable in a fraction of patients if the majority can be cured without serious toxicities.

Live donor champion: finding live kidney donors by separating the advocate from the patient

BACKGROUND

Lack of education and reluctance to initiate a conversation about live donor kidney transplantation is a common barrier to finding a donor. Although transplant candidates are often hesitant to discuss their illness, friends or family members are often eager to spread awareness and are empowered by advocating for the candidates. We hypothesized that separating the advocate from the patient is important in identifying live donors.

METHODS

We developed an intervention to train a live donor champion (LDC; a friend, family member, or community member willing to advocate for the candidate) for this advocacy role. We compared outcomes of 15 adult kidney transplant candidates who had no prospective donors and underwent the LDC intervention with 15 matched controls from our waiting list.

RESULTS

Comfort in initiating a conversation about transplantation increased over time for LDCs. Twenty-five potential donors contacted our center on behalf of LDC participants; four participants achieved live donor kidney transplantation and three additional participants have donors in evaluation, compared with zero among matched controls (P < 0.001).

CONCLUSIONS

Transplant candidates are ill equipped to seek live donors; by separating the advocate from the patient, understandable concerns about initiating conversations are reduced.

Rapid resolution of severe sustained low blood pressure in haemodialysis patients after successful renal transplantation

BACKGROUND

Low blood pressure occurring in the absence of volume depletion, anti-hypertensive medication, heart failure or cortisol deficiency occurs in ~5-10% of haemodialysis patients, and can result in serious complications. The pathophysiology of this syndrome is poorly understood.

METHODS

We describe eight cases with dialysis-associated hypotension who underwent renal transplantation. Four patients were severely hypotensive with a systolic blood pressure (SBP) <100 mmHg before and during dialysis, and four had a SBP usually <100 mmHg during dialysis, but usually >100 mmHg between sessions. All had donor-specific human leukocyte antigen antibodies. Six patients underwent pre-transplant plasmapheresis, which was curtailed in two because of further falls in blood pressure. Two patients experienced clotting of their arteriovenous fistula. In one patient cryofiltration was used, which was tolerated without severe falls in the BP. The remaining patient, who had hypotension-associated retinal vein thrombosis before transplant, was supported with an epinephrine infusion and did not receive plasmapheresis.

RESULTS

Post-transplant, the first patient did not receive pressor therapy and died from bowel ischaemia. The other seven patients were supported with inotropes on critical care. The administration of steroids did not reverse hypotension. The mean pre-treatment SBP was 96 mmHg (range 71-110, SEM 5.0). After inotropes were withdrawn and graft function was established, the mean SBP was 127 mmHg (range 113-149, SEM 4.9) (P < 0.01).

CONCLUSIONS

Renal transplantation was performed successfully and safely in patients when pressor therapy was used to treat severe dialysis-associated hypotension and, moreover, the blood pressure normalized rapidly after graft function was established.

HLA class I: an unexpected role in integrin β4 signaling in endothelial cells

The production of anti-donor antibodies to HLA class I and class II antigens following transplantation is associated with development of transplant vasculopathy and graft loss. Antibodies against HLA class I (HLA-I) molecules are thought to contribute to transplant vasculopathy by triggering signals that elicit the activation and proliferation of endothelial cells. The proximal molecular events that regulate HLA-I dependent signal transduction are not well understood. We demonstrated a mutual dependency between HLA-I and integrin β4 to stimulate signal transduction and cell proliferation. Similarly, we found that integrin β4-mediated cell migration was dependent upon its interactions with HLA-I molecules. Since integrin β4 has been implicated in angiogenesis and tumor formation, associations between integrin β4 and HLA-I may play an important role in cancer. Further characterization of interactions between HLA-I and integrin β4 may lead to the development of therapeutic strategies for the treatment and prevention of chronic allograft rejection and cancer.

Persistently low transplantation rate of ABO blood type O and highly sensitised patients despite alternative transplantation programs

ABO blood type O and highly sensitised patients have the smallest chance to receive kidney transplantation. Do alternative donation programs increase this chance? In the period studied: 2323 patients were enlisted on the Rotterdam waiting list for a renal transplantation: 435 patients still waiting (WL), 464 delisted without transplantation (DWT). 1424 received deceased donor (DD, 535) or living donor (LD, 889, including 204 alternative) transplantation. Alternative LD programs in our centre are: paired kidney-exchange, altruistic with domino-paired donation and ABO-incompatible donation (ABOi). Compared to populations not transplanted, blood type O recipients are significantly underrepresented in DD and all LD transplantation populations, except the ABOi program. Highly sensitised patients are overrepresented in DD, but underrepresented in all LD transplantation populations. The high transplantation rate of highly sensitised patients was the result of Eurotransplant Acceptable mismatch program (AM). The LD ABOi and DD AM programs are the only alternative donation programs favourable for patients with low chances. While the contribution of direct LD transplantations will increase in time, the relative success rate of low-chance patients will decrease. Beside increasing LD ABOi transplantation, a new DD allocation model favouring both highly immunised and blood type O patients is essential.

Controversies in kidney paired donation

Kidney paired donation represented 10% of living kidney donation in the United States in 2011. National registries around the world and several separate registries in the United States arrange paired donations, although with significant variations in their practices. Concerns about ethical considerations, clinical advisability, and the quantitative effectiveness of these approaches in paired donation result in these variations. For instance, although donor travel can be burdensome and might discourage paired donation, it was nearly universal until convincing analysis showed that living donor kidneys can sustain many hours of cold ischemia time without adverse consequences. Opinions also differ about whether the last donor in a chain of paired donation transplants initiated by a nondirected donor should donate immediately to someone on the deceased donor wait-list (a domino or closed chain) or should be asked to wait some length of time and donate to start another sequence of paired donations later (an open chain); some argue that asking the donor to donate later may be coercive, and others focus on balancing the probability that the waiting donor withdraws versus the number of additional transplants if the chain can be continued. Other controversies in paired donation include simultaneous versus nonsimultaneous donor operations, whether to enroll compatible pairs, and interactions with desensitization protocols. Efforts to expand public awareness of and participation in paired donation are needed to generate more transplant opportunities.

Red blood cell transfusion risks in patients with end-stage renal disease

Prior to the introduction of recombinant human erythropoietin (EPO), red blood cell (RBC) transfusions were frequently required when iron and anabolic steroids failed to improve the clinical symptoms of anemia associated with hemoglobin (Hb) levels that were commonly less than 7 g/dl. After the approval of EPO in the United States in 1989, the Hb levels of patients on hemodialysis dramatically improved and the need for RBC transfusions decreased significantly. The need for RBC transfusion remains for patients who require an immediate increase in their RBC mass due to symptomatic anemia and is likely to increase due to changes in the management of anemia in dialysis patients resulting from clinical trials data, regulatory changes, and new reimbursement policies for EPO. The safety of the blood supply has greatly improved over the last few decades, and the risk of transfusion-transmitted diseases has now been dramatically reduced. Noninfectious complications of transfusion currently cause the majority of morbidity and mortality associated with transfusion in the United States. Transfusion also brings a risk of alloimmunization, a particular concern for dialysis patients waiting for kidney transplantation. Knowledge of the risks of RBC transfusions will help clinicians better assess the risks and benefits of transfusing patients with ESRD. This article reviews the modern day infectious and noninfectious risks of allogeneic RBC transfusions.

Innovative strategies in living donor kidney transplantation

In an effort to increase living donor transplantation while minimizing risk and morbidity, recent advances have been made in surgical technique, kidney paired donation, desensitization, identification of living donors and research into living donor outcomes. Single-port nephrectomy and vaginal extraction have reduced donor nephrectomy incision size. Transport of live donor kidneys has reduced geographic barriers to kidney paired donation, and participation of compatible pairs and nondirected donors has increased match opportunities for incompatible pairs participating in this modality. ABO-incompatible transplantation can now be successfully performed without high-intensity immunomodulation, and HLA-incompatible transplantation has been shown in a large single-center study to provide profound survival benefit compared with waiting for a compatible donor. Complement inhibition is an exciting, emerging approach that may facilitate incompatible transplantation and treat antibody-mediated rejection. Educational and communications interventions are proving valuable in helping patients find living donors, and large studies continue to provide reassurance to carefully screened living donors that risks are very low. As living donors are critical to addressing the profound organ shortage, efforts to increase living donation remain important.

Racial differences in outcomes of the evaluation of potential live kidney donors: a retrospective cohort study

BACKGROUND

In the USA, the lower rate of live donor kidney transplant among Black transplant candidates may stem from lower rates of donation among potential live donors who are Black. We determined whether outcomes of the evaluation of potential live kidney donors varied according to the potential donors' demographic characteristics.

METHODS

We performed a single-center, retrospective observational cohort study of 1,179 potential live kidney donors, who came forward between 2000 and 2007. Potential donors' intended recipients were first-time transplant recipients who were evaluated between 2000 and 2005.

RESULTS

There were 268 (22.7%) potential live kidney donors who were Black, of whom 93.7% were recruited by Black transplant candidates. Donor outcomes included actual donation (38.3%), exclusion due to blood group or crossmatch incompatibility (20.4%), exclusion due to medical contraindication to donation (13.7%), and lack of further donor interest (11.2%). Black (vs. non-Black) potential donors were less likely to actually donate (27.2 vs. 41.6%, p < 0.001). Black potential donors were more likely to stop pursuing live donation (p = 0.047) or be excluded from donation for medical reasons (p = 0.008) or blood group or crossmatch incompatibility (p = 0.01). These racial differences persisted in a multivariable multinomial logistic regression model of factors associated with outcomes of the donor evaluation.

CONCLUSIONS

Potential live kidney donors who are Black are less likely to actually donate. Future studies should determine whether paired exchange and desensitization programs decrease these racial differences and why Black potential donors appear more likely to stop pursuing live donation.

The impact of donor-specific anti-HLA antibodies on late kidney allograft failure

Despite improvements in outcomes of renal transplantation, kidney allograft loss remains substantial, and is associated with increased morbidity, mortality and costs. Identifying the pathologic pathways responsible for allograft loss, and the attendant development of therapeutic interventions, will be one of the guiding future objectives of transplant medicine. One of the most important advances of the past decade has been the demonstration of the destructive power of anti-HLA alloantibodies and their association with antibody-mediated rejection (ABMR). Compelling evidence exists to show that donor-specific anti-HLA antibodies (DSAs) are largely responsible for the chronic deterioration of allografts, a condition previously attributed to calcineurin inhibitor toxicity and chronic allograft nephropathy. The emergence of sensitive techniques to detect DSAs, together with advances in the assessment of graft pathology, have expanded the spectrum of what constitutes ABMR. Today, subtler forms of rejection--such as indolent ABMR, C4d-negative ABMR, and transplant arteriopathy--are seen in which DSAs exert a marked pathological effect. In addition, arteriosclerosis, previously thought to be a bystander lesion related to the vicissitudes of aging, is accelerated in ABMR. Advances in our understanding of the pathological significance of DSAs and ABMR show their primacy in the mediation of chronic allograft destruction. Therapies aimed at B cells, plasma cells and antibodies will be important therapeutic options to improve the length and quality of kidney allograft survival.

Antibody-mediated rejection in kidney transplantation: a review

Antibody mediated rejection (AMR) poses a significant and continued challenge for long term graft survival in kidney transplantation. However, in the recent years, there has emerged an increased understanding of the varied manifestations of the antibody mediated processes in kidney transplantation. In this article, we briefly discuss the various histopathological and clinical manifestations of AMRs, along with describing the techniques and methods which have made it easier to define and diagnose these rejections. We also review the emerging issues of C4d negative AMR, its significance in long term allograft survival and provide a brief summary of the current management strategies for managing AMRs in kidney transplantation.

Infectious risks and optimal strength of maintenance immunosuppressants in rituximab-treated kidney transplantation

Background

Rituximab, an anti-CD20 antibody, effectively depletes B lymphocytes. It is not clear whether the use of conventional doses of mycophenolate mofetil (MMF), methylprednisolone and tacrolimus as maintenance immunosuppression in rituximab-treated kidney transplantation is associated with increased risk.

Methods

We retrospectively evaluated 67 patients who underwent HLA-sensitized or ABO-incompatible living donor kidney transplantation after one dose of rituximab (200 or 500 mg) (group 1). Eighty-seven kidney transplant recipients who did not require rituximab served as a control (group 2).

Results

Cytomegalovirus infection (16.4 vs. 5.7%, p = 0.031) and pneumonia (9.0 vs. 1.1%, p = 0.043) occurred more often in group 1, and 2 patients of group 1 died of infection. The doses of methylprednisolone and tacrolimus levels of the two groups were not different. MMF dose was reduced when serious infection occurred. The doses of MMF (in grams/day) at the following times postoperatively were lower in group 1 than in group 2: 1 month: 1.26 ± 0.42 vs. 1.40 ± 0.39, p = 0.033; 3 months: 1.14 ± 0.51 vs. 1.36 ± 0.39, p = 0.011; 6 months: 1.07 ± 0.50 vs. 1.30 ± 0.42, p = 0.012; 1 year: 0.88 ± 0.52 vs. 1.19 ± 0.44, p = 0.009; 2 years: 0.69 ± 0.55 vs. 1.25 ± 0.49, p = 0.059, but the reduction of MMF doses did not increase the incidence of acute rejection in group 1 (4.5% in group 1 vs. 9.2% in group 2, p = 0.351). If patients who died with functioning graft were excluded, graft survival was 98.5% in group 1 and 100% in group 2.

Conclusions

Serious infectious complications were increased in rituximab-treated kidney transplant recipients and it might be adequate to reduce the MMF dose from the early postoperative period.

Outcomes of ABO-incompatible kidney transplantation in the United States

BACKGROUND

ABO incompatible (ABOi) kidney transplantation is an important modality to facilitate living donor transplant for incompatible pairs. To date, reports of the outcomes from this practice in the United States have been limited to single-center studies.

METHODS

Using the Scientific Registry of Transplant Recipients, we identified 738 patients who underwent live-donor ABOi kidney transplantation between January 1, 1995, and March 31, 2010. These were compared with matched controls that underwent ABO compatible live-donor kidney transplantation. Subgroup analyses among ABOi recipients were performed according to donor blood type, recipient blood type, and transplant center ABOi volume.

RESULTS

When compared with ABO compatible-matched controls, long-term patient survival of ABOi recipients was not significantly different between the cohorts (P=0.2). However, graft loss was significantly higher, particularly in the first 14 days posttransplant (subhazard ratio, 2.34; 95% confidence interval, 1.43-3.84; P=0.001), with little to no difference beyond day 14 (subhazard ratio, 1.28; 95% confidence interval, 0.99-1.54; P=0.058). In subgroup analyses among ABOi recipients, no differences in survival were seen by donor blood type, recipient blood type, or transplant center ABOi volume.

CONCLUSIONS

These results support the use and dissemination of ABOi transplantation when a compatible live donor is not available, but caution that the highest period of risk is immediately posttransplant.

Antibody-mediated rejection: an evolving entity in heart transplantation

Antibody-mediated rejection (AMR) is gaining increasing recognition as a major complication after heart transplantation, posing a significant risk for allograft failure, cardiac allograft vasculopathy, and poor survival. AMR results from activation of the humoral immune arm and the production of donor-specific antibodies (DSA) that bind to the cardiac allograft causing myocardial injury predominantly through complement activation. The diagnosis of AMR has evolved from a clinical diagnosis involving allograft dysfunction and the presence of DSA to a primarily pathologic diagnosis based on histopathology and immunopathology. Treatment for AMR is multifaceted, targeting inhibition of the humoral immune system at different levels with emerging agents including proteasome and complement inhibitors showing particular promise. While there have been significant advances in our current understanding of the pathogenesis, diagnosis, and treatment of AMR, further research is required to determine optimal diagnostic tools, therapeutic agents, and timing of treatment.

Antibody-mediated kidney allograft rejection: therapeutic options and their experimental rationale

With the advent of novel therapies to directly intervene with B cell immunity and complement activation, antibody-mediated kidney allograft rejection (AMR) has come into the focus of transplant immunologists. Intravenous immunoglobulin, rituximab, bortezomib, and eculizumab have been used to treat patients with acute AMR, apart from the standard treatment of antibody removal with plasma exchange or immunoadsorption and steroid pulses. This article describes the experimental rationale and summarizes the still limited clinical experience with these novel therapies in the transplant setting. Results with the standard treatment for acute AMR, including intense plasmapheresis, intravenous immunoglobulins, and steroids are good with a graft survival of 80% at 18 months. In contrast, patients suffering from chronic AMR have significant irreversible damage in their grafts with substantially impaired graft survival. Thus, the authors propose a step-wise escalation of therapy in refractory cases of acute AMR and advocate an urgent need for controlled therapeutic trials for acute and chronic AMR not to inflict unnecessary harm on our patients by uncontrolled polypragmasy.

Banff 2011 Meeting report: new concepts in antibody-mediated rejection

The 11th Banff meeting was held in Paris, France, from June 5 to 10, 2011, with a focus on refining diagnostic criteria for antibody-mediated rejection (ABMR). The major outcome was the acknowledgment of C4d-negative ABMR in kidney transplants. Diagnostic criteria for ABMR have also been revisited in other types of transplants. It was recognized that ABMR is associated with heterogeneous phenotypes even within the same type of transplant. This highlights the necessity of further refining the respective diagnostic criteria, and is of particular significance for the design of randomized clinical trials. A reliable phenotyping will allow for definition of robust end-points. To address this unmet need and to allow for an evidence-based refinement of the Banff classification, Banff Working Groups presented multicenter data regarding the reproducibility of features relevant to the diagnosis of ABMR. However, the consensus was that more data are necessary and further Banff Working Group activities were initiated. A new Banff working group was created to define diagnostic criteria for ABMR in kidneys independent of C4d. Results are expected to be presented at the 12th Banff meeting to be held in 2013 in Brazil. No change to the Banff classification occurred in 2011.

Living donor kidney transplantation in crossmatch-positive patients enabled by peritransplant immunoadsorption and anti-CD20 therapy

Living donor kidney transplantation in crossmatch-positive patients is a challenge that requires specific measures. Ten patients with positive crossmatch results (n = 9) or negative crossmatch results but strong donor-specific antibodies (DSA; n = 1) were desensitized using immunoadsorption (IA) and anti-CD20 antibody induction. IA was continued after transplantation and accompanied by HLA antibody monitoring and protocol biopsies. After a median of 10 IA treatments, all patients were desensitized successfully and transplanted. Median levels of mean fluorescence intensity (MFI) of Luminex-DSA before desensitization were 6203 and decreased after desensitization and immediately before transplantation to 891. Patients received a median of seven post-transplant IA treatments. At last visit, after a median follow-up of 19 months, 9 of 10 patients had a functioning allograft and a median Luminex-DSA of 149 MFI; serum creatinine was 1.6 mg/dl, and protein to creatinine ratio 0.1. Reversible acute antibody-mediated rejection was diagnosed in three patients. One allograft was lost after the second post-transplant year in a patient with catastrophic antiphospholipid syndrome. We describe a treatment algorithm for desensitization of living donor kidney transplant recipients that allows the rapid elimination of DSA with a low rate of side effects and results in good graft outcome.

The role of therapeutic apheresis in high immunologic risk renal transplantation: a review of current trends

Immunologic sensitization, defined by the presence of antibodies directed against donor human leukocyte antigen (or so called donor-specific antibodies [DSA]), is common among those awaiting kidney transplantation, and is associated with worse outcomes following transplant. Existing DSA have historically been screened for pretransplant using complement-dependent cytotoxic crossmatching and their risk circumnavigated through policies that prohibit transplants between incompatible donor-recipient pairs. This risk avoidance strategy maximizes outcomes following transplant, but at the expense of limiting access to transplant for sensitized individuals. Over the last decade, the field of kidney transplantation has moved to actively modify the risks posed by DSA, rather than to simply avoid them. More sensitive detection methods have provided detailed immunologic risk stratification of potential donor-recipient pairs. Desensitization protocols, in which therapeutic aphaeresis plays a central role, have been used to reduce the potential harms posed by DSA. More recently, desensitization and paired donor exchange programs have been used in combination to expand transplantation to highly sensitized patients with incompatible living donors. It is likely that this combination of risk mitigation and avoidance strategies will be used together more often to both maximize individuals' access to transplant, and optimize patient and graft outcomes.

The utilization and advantages of an exchange donor program in living donor renal transplantation: a single-center experience

INTRODUCTION

The availability of donors is a major limiting factor in living donor renal transplantation. Approximately one third of patients with end-stage renal disease have willing potential living donors who are blood type or cross-match incompatible. The living donor kidney exchange has become an efficient solution for recipients in this situation. We analyzed the outcome and advantages of an exchange donor program compared with ABO-incompatible transplantation and desensitized protocol transplantation for highly sensitized patients.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 152 exchange donor cases from 1991 to 2010. We analyzed the risk factors, outcomes, matching factors, complication rates, and acute rejection rates of this program compared with other alternative strategies.

RESULTS

In our center, 22% of total living donor kidney transplantations were performed through an exchange program and an expanded donor pool. The graft survival, complication, and acute rejection rates were not significantly different compared with the alternatives. The severe complication rates were lower than with the alternatives and the immunosuppressant protocol and preoperative preparation were simpler. Blood type O recipients who registered in the exchange program showed no significant differences from the living related groups (P = .45), which were similar to the proportions for other ABO types. Upon multivariate analysis, an acute rejection episode and use of mycophenolate mofetil (MMF) were significant factors associated with graft survival (P = .015 and P = .007; odds ratio [OR] 5.968 and 7.324; 95% confidence interval [CI] .003-.533 and .098-.690).

CONCLUSION

Although exchange donor programs are not the sole solution, they show several advantages, such as the prescription of standard immunosuppression, simple preoperative preparation, low cost, and modest rates of severe complications compared with ABO-incompatible transplantation or desensitized protocols.

The Role of the Crossmatch in Kidney Transplantation: Past, Present and Future

Immunogenetic characterization of the transplant recipient with crossmatch is used to minimize graft loss by detecting preformed antibodies. Use of increasingly sensitive tests including flow cytometry crossmatch (FCXM) has been accompanied by near elimination of hyperacute rejection. We reviewed associations of crossmatch results with kidney graft outcomes in contemporary practice, and provided updates of our past publications with more recent data in several instances. Recent United States registry data for transplants performed with a reported positive crossmatch demonstrate immediate graft loss rates of ≤1.3% or less in FCXM+ recipients, and ≤3.6% in complement-dependent cytotoxicity crossmatch positive (CDCXM+) recipients. One-year graft survival was reduced by ≤6.4% in FCXM+ versus FCXM- recipients, and by ≤11.5% in CDCXM+ versus CDCXM- recipients. Five-year graft survival was reduced by ≤10.2 % in FCXM+ versus FCXM- recipients, and by ≤8.7% in CDCXM+ versus CDCXM- recipients. A possible explanation for the markedly lower graft loss risk with crossmatch positive transplants in modern practice may be selection of recipients with low anti-HLA titers. Although a good correlation between virtual crossmatch and actual crossmatch has been demonstrated, the outcome significance of positive virtual/negative actual and negative virtual/positive actual crossmatches is not clearly established. Post-transplant demonstration of the persistence or appearance of donor-specific antibody is of value in prognostication, but utility for adjustment of therapy is uncertain. In summary, contemporary data suggest that, among selected transplants performed, the impact of a positive crossmatch may be relatively small compared to other accepted clinical factors. Further study is warranted work to determine, prospectively, under what circumstances crossmatch positive transplants can precede with safety.

Lipids, blood pressure, kidney - what was new in 2011?

The year 2011 was very interesting regarding new studies, trials and guidelines in the field of lipidology, hypertensiology and nephrology. Suffice it to mention the new European Society of Cardiology (ESC)/European Atherosclerosis Society (EAS) guidelines on the management of dyslipidaemias, American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) guidelines on hypertension in the elderly, and many important trials presented among others during the American Society of Nephrology (ASN) Annual Congress in Philadelphia and the AHA Annual Congress in Orlando. The paper is an attempt to summarize the most important events and reports in the mentioned areas in the passing year.

Transplantation in 2011: New agents, new ideas and new hope

The past year was marked by several excellent studies that represent important therapeutic advances in kidney transplantation or that further our understanding of the genetic basis of chronic allograft dysfunction, clinical tolerance and outcomes of kidney transplantation.

Humoral immunity and antibody-mediated rejection in solid organ transplantation

The humoral arm of the immune system provides robust protection against extracellular pathogens via the production of antibody molecules that neutralize or facilitate the destruction of microorganisms. However, the humoral immune system also provides a significant barrier to solid organ transplantation due to the antibody-mediated recognition of non-self proteins and carbohydrates expressed on transplanted organs. Historically, the presence of donor-specific antibodies (DSA) that recognize donor HLA molecules, incompatible ABO blood group antigens and other endothelial or xenogeneic antigens was considered a contraindication to transplantation. However, recent advances in antibody testing and immunosuppressive therapies have made it possible to cross certain antibody barriers successfully. In this article, we review our current understanding of antibody-mediated processes in solid organ transplantation and discuss the clinically available treatment options for preventing and treating antibody-mediated rejection.