Positive cross-match living donor kidney transplantation: longer-term outcomes

Eculizumab and splenectomy as salvage therapy for severe antibody-mediated rejection after HLA-incompatible kidney transplantation

BACKGROUND

Incompatible live donor kidney transplantation is associated with an increased rate of antibody-mediated rejection (AMR) and subsequent transplant glomerulopathy. For patients with severe, oliguric AMR, graft loss is inevitable without timely intervention.

METHODS

We reviewed our experience rescuing kidney allografts with this severe AMR phenotype by using splenectomy alone (n=14), eculizumab alone (n=5), or splenectomy plus eculizumab (n=5), in addition to plasmapheresis.

RESULTS

The study population was 267 consecutive patients with donor-specific antibody undergoing desensitization. In the first 3 weeks after transplantation (median=6 days), 24 patients developed sudden onset oliguria and rapidly rising serum creatinine with marked rebound of donor-specific antibody, and a biopsy that showed features of AMR. At a median follow-up of 533 days, 4 of 14 splenectomy-alone patients experienced graft loss (median=320 days), compared to four of five eculizumab-alone patients with graft failure (median=95 days). No patients treated with splenectomy plus eculizumab experienced graft loss. There was more chronic glomerulopathy in the splenectomy-alone and eculizumab-alone groups at 1 year, whereas splenectomy plus eculizumab patients had almost no transplant glomerulopathy.

CONCLUSION

These data suggest that for patients manifesting early severe AMR, splenectomy plus eculizumab may provide an effective intervention for rescuing and preserving allograft function.

A successful bilateral lung transplantation in a patient with high panel reactive antibody and positive cross matching

A 44-year-old pregnant female patient gave stillbirth while being treated for pneumonia. She developed acute respiratory failure, which resulted in mechanical ventilator support. Diagnostic lung biopsy revealed a cryptogenic organizing pneumonia. The patient’s condition deteriorated and a venous-venous extracorporeal membrane oxygenation was placed. She was listed for lung transplantation. Because of her worsening condition lung transplantation was performed despite positive cross matching result. She was treated with rituximab, intravenous immunoglobulin, and plasmapheresis and recovered without event. There is no sign of rejection at the time of last follow-up.

Quantifying the risk of incompatible kidney transplantation: a multicenter study

Incompatible live donor kidney transplantation (ILDKT) offers a survival advantage over dialysis to patients with anti-HLA donor-specific antibody (DSA). Program-specific reports (PSRs) fail to account for ILDKT, placing this practice at regulatory risk. We collected DSA data, categorized as positive Luminex, negative flow crossmatch (PLNF) (n = 185), positive flow, negative cytotoxic crossmatch (PFNC) (n = 536) or positive cytotoxic crossmatch (PCC) (n = 304), from 22 centers. We tested associations between DSA, graft loss and mortality after adjusting for PSR model factors, using 9669 compatible patients as a comparison. PLNF patients had similar graft loss; however, PFNC (adjusted hazard ratio [aHR] = 1.64, 95% confidence interval [CI]: 1.15-2.23, p = 0.007) and PCC (aHR = 5.01, 95% CI: 3.71-6.77, p < 0.001) were associated with increased graft loss in the first year. PLNF patients had similar mortality; however, PFNC (aHR = 2.04; 95% CI: 1.28-3.26; p = 0.003) and PCC (aHR = 4.59; 95% CI: 2.98-7.07; p < 0.001) were associated with increased mortality. We simulated Centers for Medicare & Medicaid Services flagging to examine ILDKT's effect on the risk of being flagged. Compared to equal-quality centers performing no ILDKT, centers performing 5%, 10% or 20% PFNC had a 1.19-, 1.33- and 1.73-fold higher odds of being flagged. Centers performing 5%, 10% or 20% PCC had a 2.22-, 4.09- and 10.72-fold higher odds. Failure to account for ILDKT's increased risk places centers providing this life-saving treatment in jeopardy of regulatory intervention.

Transplanting the highly sensitized patient: trials and tribulations

PURPOSE OF REVIEW

Humoral sensitization to antigens of the human leukocyte antigen and ABO systems remains one of the largest barriers to further expansion in renal transplantation. This barrier translates into prolonged waiting time and a greater likelihood of death. The number of highly sensitized patients on the renal transplant waiting list continues to increase. This review focuses on the options available to these patients and speculates on future directions for incompatible transplantation.

RECENT FINDINGS

Desensitization protocols (to remove antibodies), kidney-paired donation (to circumvent antibodies) or a hybrid technique involving a combination of both have broadened the access to transplantation for patients disadvantaged by immunologic barriers. However, the risk of antibody-mediated rejection may be increased and warrants caution. Technical advances in antibody characterization using sensitive bead immunoassays and the C1q assay and therapeutic modalities such as complement inhibitors and proteasome inhibitors have been used to avoid or confront these antibody incompatibilities.

SUMMARY

A growing body of knowledge and literature indicates that these diagnostic and therapeutic modalities can facilitate a safer and more successful treatment course for these difficult-to-treat patients. Rigorous investigations into newer interventions will help in broadening the options for these patients and also expand the living donor pool.

Diagnosis and management of antibody-mediated rejection: current status and novel approaches

Advances in multimodal immunotherapy have significantly reduced acute rejection rates and substantially improved 1-year graft survival following renal transplantation. However, long-term (10-year) survival rates have stagnated over the past decade. Recent studies indicate that antibody-mediated rejection (ABMR) is among the most important barriers to improving long-term outcomes. Improved understanding of the roles of acute and chronic ABMR has evolved in recent years following major progress in the technical ability to detect and quantify recipient anti-HLA antibody production. Additionally, new knowledge of the immunobiology of B cells and plasma cells that pertains to allograft rejection and tolerance has emerged. Still, questions regarding the classification of ABMR, the precision of diagnostic approaches, and the efficacy of various strategies for managing affected patients abound. This review article provides an overview of current thinking and research surrounding the pathophysiology and diagnosis of ABMR, ABMR-related outcomes, ABMR prevention and treatment, as well as possible future directions in treatment.

B-cell tolerance in transplantation: is repertoire remodeling the answer?

T lymphocytes are the primary targets of immunotherapy in clinical transplantation; however, B lymphocytes and their secreted alloantibodies are also highly detrimental to the allograft. Therefore, the achievement of sustained organ transplant survival will likely require the induction of B-lymphocyte tolerance. During development, acquisition of B-cell tolerance to self-antigens relies on clonal deletion in the early stages of B-cell compartment ontogeny. We contend that this mechanism should be recapitulated in the setting of alloantigens and organ transplantation to eliminate the alloreactive B-cell subset from the recipient. Clinically feasible targets of B-cell-directed immunotherapy, such as CD20 and B-lymphocyte stimulator (BLyS), should drive upcoming clinical trials aimed at remodeling the recipient B-cell repertoire.

Principles of separation: indications and therapeutic targets for plasma exchange

Extracorporeal "blood purification," mainly in the form of hemodialysis has been a major portion of the clinical activity of many nephrologists for the past 5 decades. A possibly older procedure, therapeutic plasma exchange, separates and then removes plasma as a method of removing pathogenic material from the patient. In contrast to hemodialysis, therapeutic plasma exchange preferentially removes biologic substances of high molecular weight such as autoantibodies or alloantibodies, antigen-antibody complexes, and Ig paraproteins. These molecular targets may be cleared through two alternative procedures: centrifugal separation and membrane separation. This review presents operational features of each procedure, with relevance to the nephrologist. Kinetics of removal of these plasma constituents are based on the principles of separation by the apheresis technique and by features specific to each molecular target, including their production and compartmentalization in the body. Molecular targets for common renal conditions requiring therapeutic plasma exchange are also discussed in detail.

Allocation and matching in kidney exchange programs

Living donor kidney transplantation is the preferred treatment for patients suffering from end-stage renal disease. To alleviate the shortage of kidney donors, many advances have been made to improve the utilization of living donors deemed incompatible with their intended recipient. The most prominent of these advances is kidney paired donation (KPD), which matches incompatible patient-donor pairs to facilitate a kidney exchange. This review discusses the various approaches to matching and allocation in KPD. In particular, it focuses on the underlying principles of matching and allocation approaches, the combination of KPD with other strategies such as ABO incompatible transplantation, the organization of KPD, and important future challenges. As the transplant community strives to balance quantity and equity of transplants to achieve the best possible outcomes, determining the right long-term allocation strategy becomes increasingly important. In this light, challenges include making full use of the various modalities that are now available through integrated and optimized matching software, encouragement of transplant centers to fully participate, improving transplant rates by focusing on the expected long-run number of transplants, and selecting uniform allocation criteria to facilitate international pools.

Analysis of anti-HLA antibodies in sensitized kidney transplant candidates subjected to desensitization with intravenous immunoglobulin and rituximab

BACKGROUND

Preexisting donor-specific antibodies against human leukocyte antigens are major risk factors for acute antibody-mediated and chronic rejection of kidney transplant grafts. Immunomodulation (desensitization) protocols may reduce antibody concentration and improve the success of transplant. We investigated the effect of desensitization with intravenous immunoglobulin and rituximab on the antibody profile in highly sensitized kidney transplant candidates.

METHODS

In 31 transplant candidates (calculated panel-reactive antibody [cPRA], 34%-99%), desensitization included intravenous immunoglobulin on days 0 and 30 and a single dose of rituximab on day 15. Anti-human leukocyte antigen antibodies were analyzed before and after desensitization.

RESULTS

Reduction of cPRA from 25% to 50% was noted for anti-class I (5 patients, within 20-60 days) and anti-class II (3 patients, within 10-20 days) antibodies. After initial reduction of cPRA, the cPRA increased within 120 days. In 24 patients, decrease in mean fluorescence intensity of antibodies by more than 50% was noted at follow-up, but there was no reduction of cPRA. Rebound occurred in 65% patients for anti-class I antibodies at 350 days and anti-class II antibodies at 101 to 200 days. Probability of rebound effect was higher in patients with mean fluorescence intensity of more than 10,700 before desensitization, anti-class II antibodies, and history of previous transplant.

CONCLUSIONS

The desensitization protocol had limited efficacy in highly sensitized kidney transplant candidate because of the short period with antibody reduction and high frequency of rebound effect.

Kidney transplantation across HLA and ABO antibody barriers

PURPOSE OF REVIEW

A significant number of kidney transplantations in industrialized countries is currently performed over human leukocyte antigen (HLA) or ABO antibody barriers after living donation to encounter the increasing shortage of organs from deceased donors. Although patients with moderate titers of anti-A/B antibodies may easily be desensitized with no negative impact on allograft survival, recipients with high titers and HLA sensitized patients demonstrate a substantial risk for antibody-mediated rejection, limiting long-term outcomes.

RECENT FINDINGS

The use of powerful desensitization strategies including plasmapheresis and immunoadsorption, extended therapeutic options such as the application of the recently introduced complement inhibitors, and refined antibody detection techniques may further facilitate transplantations, especially in the HLA-sensitized kidney transplant recipient. On the contrary, special strategies such as the Eurotransplant Acceptable Mismatch Program or kidney paired exchange help improving long-term outcomes in these difficult to transplant patients by circumventing the HLA (or ABO) antibody barrier.

SUMMARY

As compared with waiting for a compatible deceased donor organ, HLA and ABO incompatible transplantations performed in experienced centers have become a reasonable alternative for end-stage kidney disease patients with an incompatible live donor. Whenever possible, however, the transplantation should be performed between ABO compatible donor-recipient pairs in the absence of positive crossmatch results.

Early versus late acute antibody-mediated rejection in renal transplant recipients

BACKGROUND

Over the last decade, the diagnostic precision for acute antibody-mediated rejection (aABMR) in kidney transplant recipients has improved significantly. The phenotypes of early and late aABMR may differ. We assessed the characteristics and outcomes of early versus late aABMR.

METHODS

Between January 1, 2005 and December 31, 2010, aABMR was diagnosed in 67 grafts in 65 kidney recipients, with a median follow-up of 3.6 years (range, 61 days-7.3 years). Recipients were stratified by early aABMR (<3 months after transplantation; n=40) and late aABMR (>3 months after transplantation; n=27). The main outcome was kidney allograft loss. Outcome of aABMR was compared with recipients with acute early (n=276) or late (n=100) non-ABMR during the same period.

RESULTS

Recipients with late aABMR had significantly reduced graft survival compared with recipients with early aABMR (P<0.001, log-rank test; 40% vs. 75% at 4 years; hazard ratio, 3.72; 95% confidence interval, 1.65-8.42). Graft survival in late aABMR was also inferior to late non-ABMR acute rejections (P=0.008). At transplantation, more patients were presensitized to human leukocyte antigens (22 [55%] vs. 4 [15%] in the early vs. late aABMR group). The late aABMR group was characterized by younger recipient age (37.9 ± 12.9 vs. 50.9 ± 11.6 years; P<0.001), increased occurrence of de novo donor-specific antibodies (52% vs. 13%; P=0.001), and nonadherence/suboptimal immunosuppression (56% vs. 0%; P<0.001).

CONCLUSION

Compared with early aABMR, late aABMR had inferior graft survival and was characterized by young age, frequent nonadherence, or suboptimal immunosuppression and de novo donor-specific antibodies.

Desensitization combined with paired exchange leads to successful transplantation in highly sensitized kidney transplant recipients: strategy and report of five cases

Sensitization remains a major barrier to kidney transplantation. Sensitized patients comprise 30% of the kidney transplant waiting list but fewer than 15% of highly sensitized patients are transplanted each year. Options for highly sensitized patients with an immunologically incompatible living donor include desensitization or kidney paired donation (KPD). However, these options when used alone may still not be sufficient to allow a compatible transplant for recipients who are broadly sensitized with cumulative calculated panel-reactive antibody (cPRA) > 95%. We describe in this report the combined use of both desensitization and KPD to maximize the likelihood of finding a compatible match with a more immunologically favorable donor through a kidney exchange program. This combined approach was used in five very highly sensitized patients, all with cPRA 100%, who ultimately received compatible living and deceased donor kidney transplants. We conclude that early enrollment in paired kidney donor exchange and tailored desensitization protocols are key strategies to improve care and rates of kidney transplantation in highly sensitized patients.

Kidney paired donation in the presence of donor-specific antibodies

Incompatible donor/recipient pairs with broadly sensitized recipients have difficulty finding a crossmatch-compatible match, despite a large kidney paired donation pool. One approach to this problem is to combine kidney paired donation with lower-risk crossmatch-incompatible transplantation with intravenous immunoglobulin. Whether this strategy is non-inferior compared with transplantation of sensitized patients without donor-specific antibody (DSA) is unknown. Here we used a protocol including a virtual crossmatch to identify acceptable crossmatch-incompatible donors and the administration of intravenous immunoglobulin to transplant 12 HLA-sensitized patients (median calculated panel reactive antibody 98%) with allografts from our kidney paired donation program. This group constituted the DSA(+) kidney paired donation group. We compared rates of rejection and survival between the DSA(+) kidney paired donation group with a similar group of 10 highly sensitized patients (median calculated panel reactive antibody 85%) that underwent DSA(-) kidney paired donation transplantation without intravenous immunoglobulin. At median follow-up of 22 months, the DSA(+) kidney paired donation group had patient and graft survival of 100%. Three patients in the DSA(+) kidney paired donation group experienced antibody-mediated rejection. Patient and graft survival in the DSA(-) kidney paired donation recipients was 100% at median follow-up of 18 months. No rejection occurred in the DSA(-) kidney paired donation group. Thus, our study provides a clinical framework through which kidney paired donation can be performed with acceptable outcomes across a crossmatch-incompatible transplant.

Approach to kidney transplant in sensitized potential transplant recipients

More than one-third of patients on waiting lists for kidney transplant are sensitized. Most have previously formed donor-specific and non-donor-specific serum antibodies and/or positive crossmatch by complement-dependent cytotoxity and/or flow cytometry. Two categories of alloantibodies include antibodies against major histocompatibility complex human leukocyte antigen class 1 and class 2 and antibodies against minor histocompatibility complex. A current positive crossmatch is an absolute contraindication for transplant. Positive historical panel reactive antibody and/or donor-specific antibodies (human leukocyte antigen and minor histocompatibility complex), even in the absence of a historical positive crossmatch, are associated with an increased risk for allosensitization, antibodymediated rejection, and accelerated graft failure. Desensitization protocols are numerous, complex, and expensive. It is recommended to perform a systematic determination of historical and current panel reactive antibody, donor-specific antibodies (human leukocyte antigen and minor histocompatibility complex), and crossmatch by the most sensitive assays. The risk of sensitization may be estimated from the combined results of the crossmatch with the donor and those of the recipient's panel reactive antibody and donor-specific antibodies at baseline. The adoption of a scoring system for risk stratification may facilitate the task of organ allocation for sensitized patients. Recipients with an estimated sensitization risk ≥ high may be referred preferably to the national waiting priority list and informed about the financial and the medical risks that may incur with future transplant. Sensitized patients at high risk for antibody-mediated rejection may benefit from a structured monitoring process involving systematic and regular immunologic, histologic, and functional assessments of the graft after transplant. We recommend the adoption and regular updating of these approaches to ensure safe and appropriate therapeutic standards in these sensitized patients, in accordance with best clinical practice.

Five-year outcomes in living donor kidney transplants with a positive crossmatch

Renal transplant candidates with high levels of donor-specific anti-HLA antibodies have low transplantation rates and high mortality rates on dialysis. Using desensitization protocols, good short-term outcomes are possible in "positive crossmatch kidney transplants (+XMKTx)", but long-term outcome data are lacking. The aim of the current study was to determine actual 5-year graft outcomes of +XMKTx. We compared graft survival and the functional and histologic status of 102 +XMKTx to 204 -XMKTx matched for age and sex. Actual 5-year death-censored graft survival was lower in the +XMKTx group (70.7% vs. 88.0%, p < 0.01) and chronic injury (glomerulopathy) was present in 54.5% of surviving grafts. Graft survival was higher in recipients with antibody against donor class I only compared with antibody against class II (either alone or in combination with class I) (85.3% vs. 62.6%, p = 0.05) and was similar to -XMKTx (85.3 vs. 88.0%, p = 0.64). Renal function and proteinuria ranged across a wide spectrum in all groups reflecting the different histological findings at 5 years. We conclude that when compared to -XMKTx, +XMKTx have inferior outcomes at 5 years, however, almost half of the surviving grafts do not have glomerulopathy and avoiding antibodies against donor class II may improve outcomes.

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.

The role of complement in antibody-mediated rejection in kidney transplantation

Over the past decade, several studies have suggested that the complement system has an active role in both acute and chronic allograft rejection. These studies have been facilitated by improved techniques to detect antibody-mediated organ rejection, including immunohistological staining for C4d deposition in the allograft and solid-phase assays that identify donor-specific alloantibodies (DSAs) in the serum of transplant recipients. Studies with eculizumab, a humanized monoclonal antibody directed against complement component C5, have shown that activation of the terminal complement pathway is necessary for the development of acute antibody-mediated rejection in recipients of living-donor kidney allografts who have high levels of DSAs. The extent to which complement activation drives chronic antibody-mediated injury leading to organ rejection is less clear. In chronic antibody-mediated injury, early complement activation might facilitate chemotaxis of inflammatory cells into the allograft in a process that later becomes somewhat independent of DSA levels and complement factors. In this Review, we discuss the different roles that the complement system might have in antibody-mediated allograft rejection, with specific emphasis on renal transplantation.

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.

Chain transplantation: initial experience of a large multicenter program

We report the results of a large series of chain transplantations that were facilitated by a multicenter US database in which 57 centers pooled incompatible donor/recipient pairs. Chains, initiated by nondirected donors, were identified using a computer algorithm incorporating virtual cross-matches and potential to extend chains. The first 54 chains facilitated 272 kidney transplants (mean chain length = 5.0). Seven chains ended because potential donors became unavailable to donate after their recipient received a kidney; however, every recipient whose intended donor donated was transplanted. The remaining 47 chains were eventually closed by having the last donor donate to the waiting list. Of the 272 chain recipients 46% were ethnic minorities and 63% of grafts were shipped from other centers. The number of blood type O-patients receiving a transplant (n = 90) was greater than the number of blood type O-non-directed donors (n = 32) initiating chains. We have 1-year follow up on the first 100 transplants. The mean 1-year creatinine of the first 100 transplants from this series was 1.3 mg/dL. Chain transplantation enables many recipients with immunologically incompatible donors to be transplanted with high quality grafts.

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 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.

Human leukocyte antigen antibody-incompatible renal transplantation: excellent medium-term outcomes with negative cytotoxic crossmatch

BACKGROUND

Human leukocyte antigen (HLA) antibody-incompatible renal transplantation has been increasingly performed since 2000 but with few data on the medium-term outcomes.

METHODS

Between 2003 and 2011, 84 patients received renal transplants with a pretreatment donor-specific antibody (DSA) level of more than 500 in a microbead assay. Seventeen patients had positive complement-dependent cytotoxic (CDC) crossmatch (XM), 44 had negative CDC XM and positive flow cytometric XM, and 23 had DSA detectable by microbead only. We also reviewed 28 patients with HLA antibodies but no DSA at transplant. DSAs were removed with plasmapheresis pretransplant, and patients did not routinely receive antithymocyte globulin posttransplant.

RESULTS

Mean follow-up posttransplantation was 39.6 (range 2-91) months. Patient survival after the first year was 93.8%. Death-censored graft survival at 1, 3, and 5 years was 97.5%, 94.2%, and 80.4%, respectively, in all DSA+ve patients, worse at 5 years in the CDC+ve than in the CDC-ve/DSA+ve group at 45.6% and 88.6%, respectively (P<0.03). Five-year graft survival in the DSA-ve group was 82.1%. Rejection occurred in 53.1% of DSA+ve patients in the first year compared with 22% in the DSA-ve patients (P<0.003).

CONCLUSIONS

HLA antibody-incompatible renal transplantation had a high success rate if the CDC XM was negative. Further work is required to predict which CDC+ve XM grafts will be successful and to treat slowly progressive graft damage because of DSA in the first few years after transplantation.

The utility of comprehensive assessment of donor specific anti-HLA antibodies in the clinical management of pediatric kidney transplant recipients

Advances in anti-HLA antibody characterization have had a major impact on kidney transplantation. Comprehensive characterization of DSA has improved protocols for allosensitized transplant candidates, increasing access to acceptable donors. Sensitive and specific solid phase antibody detection assays have given important insight into the clinical characteristics of antibody-mediated allograft injury, resulting in the development of a classification system for acute AMR. In addition, important insights into the nature of chronic antibody-mediated allograft rejection have been achieved as a result of improvements in DSA characterization. Finally, assays initially developed as tools to detect DSA in the clinical setting have been employed in innovative research protocols, allowing the investigation of new therapeutic approaches.

Luminex-based desensitization protocols: the University of Wisconsin initial experience

BACKGROUND

We have demonstrated that immunodominant donor-specific antibody (DSA) more than 100 mean fluorescence intensity (MFI) at the time of transplant is associated with a significantly higher risk of rejection. We now present short-term outcomes of DSA-based desensitization (DSZ) strategies in patients with a negative complement-dependent cytotoxicity crossmatch.

METHODS

Between January 1, 2009, and January 1, 2010, live-donor kidney transplant recipients were divided into three protocols based on their immunodominant DSA MFI pretransplant (D1: 100-500, D2: 501-1000, and D3: 1001-3000). Deceased donor kidney transplant recipients were stratified into two protocols (D4: 501-1000 and D5: 1001-3000). The intensity of the conditioning treatment increased with DSA levels and included thymoglobulin induction, plasmapheresis, and intravenous immunoglobulin in the highest risk groups. We compared outcomes between desensitized patients (DSZ) and those undergoing no DSZ (or D0) during the same interval.

RESULTS

Forty-eight of 249 (23%) kidney transplants underwent DSZ (n=20, 4, 3, 4, and 17 in D1-D5 protocols, respectively). There was more retransplantation (50% vs. 18%, P<0.001) and live donor transplantation (56% vs. 30%, P<0.001) in the DSZ group. In this group, mean peak panel reactive antibody and MFI at transplant were 51% ± 7% and 960 ± 136, respectively. The incidence of antibody-mediated rejection (25% vs. 12.5%, P=0.008) and acute cellular rejection (23% vs. 14%, P=0.02) was greater in the DSZ group. However, mixed rejection (8%), graft loss (0 vs. 6), patient death (0 vs. 3), cytomegalovirus infection (15% vs. 12%), and 1-year serum creatinine (1.4 ± 0.5 and 1.4 ± 0.4 mg/dL) were similar between DSZ and no-DSZ groups. CONCLUSION.: Long-term follow-up is needed to determine the role of Luminex-based strategies in current preconditioning regimens.

Desensitization in HLA-incompatible kidney recipients and survival

BACKGROUND

More than 20,000 candidates for kidney transplantation in the United States are sensitized to HLA and may have a prolonged wait for a transplant, with a reduced transplantation rate and an increased rate of death. One solution is to perform live-donor renal transplantation after the depletion of donor-specific anti-HLA antibodies. Whether such antibody depletion results in a survival benefit as compared with waiting for an HLA-compatible kidney is unknown.

METHODS

We used a protocol that included plasmapheresis and the administration of low-dose intravenous immune globulin to desensitize 211 HLA-sensitized patients who subsequently underwent renal transplantation (treatment group). We compared rates of death between the group undergoing desensitization treatment and two carefully matched control groups of patients on a waiting list for kidney transplantation who continued to undergo dialysis (dialysis-only group) or who underwent either dialysis or HLA-compatible transplantation (dialysis-or-transplantation group).

RESULTS

In the treatment group, Kaplan-Meier estimates of patient survival were 90.6% at 1 year, 85.7% at 3 years, 80.6% at 5 years, and 80.6% at 8 years, as compared with rates of 91.1%, 67.2%, 51.5%, and 30.5%, respectively, for patients in the dialysis-only group and rates of 93.1%, 77.0%, 65.6%, and 49.1%, respectively, for patients in the dialysis-or-transplantation group (P<0.001 for both comparisons).

CONCLUSIONS

Live-donor transplantation after desensitization provided a significant survival benefit for patients with HLA sensitization, as compared with waiting for a compatible organ. By 8 years, this survival advantage more than doubled. These data provide evidence that desensitization protocols may help overcome incompatibility barriers in live-donor renal transplantation. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the Charles T. Bauer Foundation.).

Incompatible live-donor kidney transplantation in the United States: results of a national survey

BACKGROUND AND OBJECTIVES

Use of incompatible kidney transplantation (IKT) is growing as a response to the organ shortage and the increase in sensitization among candidates. However, recent regulatory mandates possibly threaten IKT, and the potential effect of these mandates cannot be estimated because dissemination of this modality remains unknown. The goal of this study was to better understand practice patterns of IKT in the United States.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Directors from all 187 unique active adult kidney transplant programs were queried about transplantation across the following antibody barriers: positive Luminex, negative flow crossmatch (PLNF); positive flow, negative cytotoxic crossmatch (PFNC); positive cytotoxic crossmatch (PCC); and ABO incompatible (ABOi).

RESULTS

Responses from 125 centers represented 84% of the live-donor transplant volume in the United States. Barriers of PLNF, PFNC, PCC, and ABOi are being crossed in 70%, 51%, 18%, and 24%, respectively, of transplant centers that responded. Desensitization was performed in 58% of PLNF, 76% of PFNC, 100% of PCC, and 80% of ABOi using plasmapheresis and low-dose intravenous Ig (IVIg) in 71% to 83% and high-dose IVIg in 29% to 46%.

CONCLUSIONS

A higher proportion of centers perform IKT than might be inferred from the literature. The rapid dissemination of these protocols despite adequate evidence of a clear advantage of IKT transplants argues for the creation of a national registry and randomized studies.

Desensitization protocols and their outcome

In the last decade, transplantation across previously incompatible barriers has increasingly become popular because of organ donor shortage, availability of better methods of detecting and characterizing anti-HLA antibodies, ease of diagnosis, better understanding of antibody-mediated rejection, and the availability of effective regimens. This review summarizes all manuscripts published since the first publication in 2000 on desensitized patients and discusses clinical outcomes including acute and chronic antibody-mediated rejection rate, the new agents available, kidney paired exchange programs, and the future directions in sensitized patients. There were 21 studies published between 2000 and 2010, involving 725 patients with donor-specific anti-HLA antibodies (DSAs) who underwent kidney transplantation with different desensitization protocols. All studies were single center and retrospective. The patient and graft survival were 95% and 86%, respectively, at a 2-year median follow-up. Despite acceptable short-term patient and graft survivals, acute rejection rate was 36% and acute antibody-mediated rejection rate was 28%, which is significantly higher than in nonsensitized patients. Recent studies with longer follow-up of those patients raised concerns about long-term success of desensitization protocols. The studies utilizing protocol biopsies in desensitized patients also reported higher subclinical and chronic antibody-mediated rejection. An association between the strength of DSAs determined by median fluorescence intensity values of Luminex single-antigen beads and risk of rejection was observed. Two new agents, bortezomib, a proteasome inhibitor, and eculizumab, an anti-complement C5 antibody, were recently introduced to desensitization protocols. An alternative intervention is kidney paired exchange, which should be considered first for sensitized patients.

Kidney transplantation in highly sensitized patients: are there options to overcome a positive crossmatch?

Presensitization against a broad array of human leukocyte antigens (HLA) is associated with prolonged waiting times and inferior graft survival in kidney transplantation. Since the late 1960s, a positive lymphocytotoxic crossmatch has been considered a contraindication for kidney transplantation and solutions, such as enrollment of eligible patients in the Acceptable Mismatch Program of Eurotransplant and kidney paired donation in the case of living donor kidney transplantation, have been proposed to avoid this barrier. Alternatively, a positive crossmatch might not be considered as a contraindication for kidney transplantation and one can try to overcome this hurdle by desensitization. In principle, there are three different ways to overcome the crossmatch barrier by desensitization. The highly sensitized patient awaiting a cadaveric kidney transplant may be desensitized either immediately pretransplant when an organ is offered or in advance, during the time on the waiting list, to increase his chance of having a negative crossmatch at the time of transplantation. In the case of living donor kidney transplantation, the patient can be desensitized for days to weeks until the positive crossmatch with his intended living kidney donor becomes negative. "Heidelberg algorithm" is a combination of different measures, such as pretransplant risk estimation, good HLA match, inclusion of patients in the Eurotransplant Acceptable Mismatch program, and desensitization, which leads to timely transplantation and excellent survival rates in highly sensitized patients at a low rate of toxicity. We believe that all available options should be utilized in an integrated manner for the transplantation of kidney transplant recipients who are at a high risk of antibody-mediated rejection.