Antigen-specific Immunoadsorption Research Articles

Successful Treatment of Severe ABO Antibody-Mediated Rejection Using Bortezomib: A Case Report

BackgroundOur program for ABO-incompatible renal transplantation includes antigen-specific immunoadsorption (extracorporeal columns with the A or B trisaccharides), rituximab, and standard maintenance immunosuppression. Anti-A or -B titers ≤8 in the indirect antiglobulin test (IAT) against panel A1 or B RBC are acceptable for transplantation. Case ReportA previously healthy, 15-month-old girl was diagnosed with Wilms' tumor and proteinuria. Denys–Drash syndrome was confirmed. Bilateral nephrectomy was performed. At 3.5 years of age she received an ABO-incompatible renal transplant from her father (A1 to O). The anti-A titers before transplantation were low. She was treated preoperatively with rituximab, immunoadsorption, immunoglobulin and mycophenolate mofetil (MMF). The maintenance immunosuppression protocol included basiliximab, tacrolimus, MMF, and prednisolone. The initial postoperative course was uncomplicated with rapid normalization of serum creatinine. The anti-A titers started to increase on postoperative day 5 (8 NaCl/16 IAT). Despite daily immunoadsorptions the titers rose to 1024 NaCl/1024 IAT on day 9. Renal function deteriorated and hemodialysis was started. A renal biopsy on day 9 showed acute severe antibody-mediated rejection. Additional treatment with bortezomib was given and after 2 doses the titers started to decline, renal allograft function improved and hemodialysis was stopped. On day 21 posttransplant the titers went down, creatinine was 28 μmol/L, and no more immunoadsorptions were performed. ConclusionBy using bortezomib, we were able to successfully reverse a severe ABO antibody-mediated rejection.

ABO-Incompatible Kidney Transplantation Enabled by Non-Antigen-Specific Immunoadsorption

ABO-incompatible kidney transplantation performed after desensitization with antigen-specific immunoadsorption (IA) results in good outcomes. However, a unique single-use IA device is required, which creates high costs. From August 2005 to August 2010, 19 patients were desensitized for ABO-incompatible living donor kidney transplantation. Six patients treated with a single-use antigen-specific IA device and 12 patients treated with a reusable non-antigen-specific IA device were analyzed. Six patients who received antigen-specific IA had a median of 5 IA treatments and 12 patients with non-antigen-specific IA had a median of 6 IA treatments preoperatively. Median average titer drop in Coombs technique was 1.2 in antigen-specific IA and 1.7 in non-antigen-specific IA. In two patients with antigen-specific IA and four patients with non-antigen-specific IA, additional plasmapheresis treatments were necessary for recipient desensitization. Despite six treatments with antigen-specific IA and 12 plasmapheresis treatments, one patient with a starting isoagglutinin titer of 1:1024 (Coombs) could not be transplanted. The 18-month graft survival rate for the 17 ABO-incompatible living donor kidney transplants was 100%. One male recipient who was desensitized with antigen-specific IA died 44 months after transplantation from sudden cardiac death with a serum creatinine of 1.2 mg/dL. At last follow-up, a median of 13 months after transplantation, median serum creatinine for 16 patients was 1.5 mg/dL, median glomerular filtration rate as estimated by the modification of diet in renal disease formula 54 mL/min/1.73 m, and median urinary protein-to-creatinine ratio 0.1, with no differences between treatments. A reusable non-antigen-specific IA device allows high number of treatments at reasonable cost, and at the same time might deplete human leukocyte antigen-alloantibodies.

Desensitization With Antigen-Specific Immunoadsorption Interferes With Complement in ABO-Incompatible Kidney Transplantation

Complement activation was characterized during and after desensitization treatment in 19 consecutive patients receiving ABO-incompatible (ABOi) living donor kidney transplants to assess the effect of desensitization protocol including antigen-specific immunoadsorption (IA) on complement activation. All patients received rituximab- and tacrolimus-based triple treatment. Anti-A/B antibodies were removed by IA. Serial determinations of C3, C3a, the C3a/C3 ratio, and sC5b-9 were carried out between day -30 and postoperative day 30. C1q was measured on day -30 and the day before the transplantation. In two recipients, eluates from immunoadsorbent columns were analyzed for C3a, C1q, and immunoglobulins by western blotting. Same complement analysis was performed in eluate from a control column after in vitro perfusion of AB-plasma. Patient and graft survival were 100% for a median follow-up of 40 months (range, 12-60 months). There were no humoral rejections based on ABO-antigen-antibody interactions. C3a and the C3a/C3 ratio declined with the start of IA treatment, and this decline was maintained postoperatively. C1q declined from day -30 to a lower value on the day before transplantation (P<0.05). In eluates from both patient and control, immunoadsorbent column immunoglobulins together with C3a and C1q were detected. The current protocol including antigen-specific IA interferes with the complement system; this effect may be partially responsible for the absence of humoral rejection resulting from ABO-antigen-antibody interactions and the excellent outcomes obtained after ABO-incompatible kidney transplantation.

The efficacy of antigen-specific immunoadsorption and rebound of anti-A/B antibodies in ABO-incompatible kidney transplantation

As antigen-specific immunoadsorption (IA) using the Glycosorb®-ABO columns is becoming increasingly popular in ABO-incompatible (ABOi) transplantation, in this study, we retrospectively investigated the efficacy of Glycosorb®-ABO IA in vivo and ex vivo. We also assessed the risk of anti-A/B antibody (ABab) rebound before and after ABOi kidney transplantation. A protocol for ABOi living donor kidney transplantation was used, combining four preoperative and three preemptive postoperative Glycosorb®-ABO IAs with rituximab and maintenance immunosuppression. ABabs were determined by a haemagglutination titration technique. ABOi kidney transplantation was attempted 45 times and 43 transplantations were performed. Overall patient survival was 93% and graft survival was 91%. Mean follow-up was 4.5 years. Glycosorb®-ABO IA significantly reduced the ABabs in the majority of patients (P < 0.0001). However, in three patients (6.8%), the antibody elimination was incomplete. Inadequate adsorption of core-chain-dependent ABabs may explain this finding, but further studies are needed. In five patients, the preconditioning was interrupted before transplantation, resulting in ABab rebound. Yet, when preconditioning was restarted, the antibodies could be removed as planned. After ABOi transplantation, rebound of ABabs was seen in two patients (5%). Glycosorb®-ABO IA in combination with rituximab effectively depletes ABabs in most patients, but owing to core-chain-dependent ABabs, Glycosorb®-ABO IA may be less effective than nonspecific techniques for antibody removal in some patients. Rebound before transplantation subsequent to interrupted preconditioning does not hamper a successful ABOi transplantation. Postoperatively, when this protocol for ABOi transplantation is followed, the risk of ABab rebound is small.

ABO‐incompatible kidney transplantation in children

We designed a new protocol to enable safe ABO-incompatible kidney transplantation. The new protocol utilizes antigen-specific immunoadsorption rather than unspecific plasma exchange to remove existing anti A/B antibodies and rituximab rather than splenectomy to prevent rebound of antibodies. Sixty patients have so far been successfully transplanted with this protocol and 10 of those have been children. When compared with ABO-compatible transplantations, we could not find any differences in success rate, renal function, or adverse events.

ABO-incompatible renal transplantation: From saline flushes to antigen-specific immunoadsorption-Tools to overcome the barrier

On April 23, 1951, a 30-year-old woman received the first intentional ABOi (ABO incompatible) renal transplantation in Boston. At that time, it was commonly believed that intensely rinsing the graft to remove blood would be sufficient to overcome any immunological problems associated with blood type incompatibility. However, when the abovementioned patient and another ABOi transplant recipient died within a month, Humes and colleagues arrived at the same conclusion: "We do not feel that renal transplantation in the presence of blood incompatibility is wise." In the decades that followed, we learned that the oligosaccharide surface antigens representing the ABO-blood group antigens are expressed not only on erythrocytes but also on cells from various tissues, including the vascular endothelium. The growing gap between organ demand and availability has sparked efforts to overcome the ABO barrier. After its disappointing results in the early 1970s, Japan became the leader of this endeavor in the 1980s. All protocols are based on 2 strategies: removal of preformed antibodies with extracorporeal techniques and inhibition of ongoing antibody production. Successful ABOi renal transplantation became possible with the advent of splenectomy, new immunosuppressive drugs (e.g., rituximab, a monoclonal antibody against CD20), and extracorporeal methods such as antigen-specific immunoadsorption. This review summarizes the underlying pathophysiology of ABOi transplantation and the different protocols available. Further, we briefly touch potential short- and long-term problems, particularly the incidence of infectious complications and malignancies, that can arise with high-intensity immunosuppressive therapy.

Isoagglutinin adsorption in ABO-incompatible transplantation

As the demand for kidney transplantation is constantly growing methods to expand the donor pool have become increasingly important. ABO-incompatibility has hitherto been regarded as an absolute contraindication to living donor donation. However, as ABO-incompatibility has accounted for the majority of living donor exclusions, efforts have been made to overcome this immunologic barrier. Successful desensitization protocols thus far, have combined plasmapheresis for antibody removal with splenectomy to reduce the antibody producing B-cell pool, in addition to quadruple immunosuppression. Although good graft function has been achieved, the high risks involved have been deterrent. We have developed a protocol for ABO-incompatible kidney transplantation based on antigen-specific immunoadsorption and rituximab, in combination with standard maintenance immunosuppression (tacrolimus, mycophenolate mofetil and corticosteroids). We hypothesized that the anti-A/B antibodies could be effectively eliminated and good graft function achieved, without the complications of coagulopathy and transfusion reactions associated with plasmapheresis. Furthermore, we hypothesized that the substitution of splenectomy with a single dose of the anti-CD20 antibody rituximab would further reduce surgical risk as well as the risk of infectious complications. In 2001 the program for ABO-incompatible kidney transplantation was started at our center. To date 50 ABO-incompatible kidney transplantations have been performed according to the protocol based on antigen-specific immunoadsorption and rituximab. Safety and efficacy of the protocol has been evaluated in several studies, all showing that the antigen-specific immunoadsorption is well tolerated and without any serious side effects. Patient and graft survival as well as kidney function have been comparable to that of ABO-compatible living donor kidney transplantation and the incidence of antibody-mediated rejection 0%. We conclude that AB0-incompatible kidney transplantation using a protocol based on antigen-specific immunoadsorption and rituximab, in combination with triple immunosuppressive therapy is safe and effective. ABO-incompatibility following this protocol does not have a negative impact on graft function. ABO-incompatible kidney transplantation is equivalent to standard ABO-compatible living donor kidney transplantation.

Long-term outcome of ABO-incompatible living donor kidney transplantation based on antigen-specific desensitization. An observational comparative analysis

ABO-incompatible living donor kidney transplantation based on specific conditioning has been successfully adopted by transplant centres worldwide. Excellent short-term results have been reported in small cohorts. However, long-term data and comparative analyses are still sparse. We report on the outcome of 40 consecutive ABO-incompatible living donor kidney transplant recipients and compare their clinical course to a control group of 43 ABO-compatible living donor transplant patients transplanted during the same time period. This is an observational single-centre analysis of 40 consecutive patients undergoing ABO-incompatible kidney grafting between April 2004 and April 2009, using a protocol of rituximab, antigen-specific immunoadsorption, intravenous immunoglobulin, basiliximab induction and oral triple immunosuppression with tacrolimus, mycophenolic acid and prednisone. Forty-three ABO-compatible kidney transplant recipients served as controls. The control group had also received basiliximab induction and an identical initial maintenance immunosuppression. The two groups were observed for an average of 39 and 19 months, respectively. There was a significantly higher incidence of lymphoceles requiring surgical revisions in the ABO-incompatible group. However, this surgical complication did not affect patient or graft survival. Mean serum creatinine, estimated glomerular filtration rate and proteinuria did not differ between the two groups. Furthermore, ABO-incompatible and ABO-compatible patients had the same incidence of humoral and cellular rejections. Despite a more aggressive induction therapy, no differences in infectious or malignant complications were observed. ABO-incompatible living donor kidney transplantation utilizing a combination of rituximab and antigen-specific immunoadsorption yielded results identical to ABO-compatible transplantation despite a significantly higher number of human leukocyte antigen mismatches.

Successful Long‐term Outcome of ABO‐incompatible Liver Transplantation Using Antigen‐specific Immunoadsorption Columns

ABO-incompatible (ABO-I) liver transplantation has been performed essentially in patients with acute liver failure awaiting an urgent liver transplantation. Early results with ABO-I liver transplantation were disappointing with a very low graft survival rate (20-50%). The main risk is the occurrence of severe humoral and cellular rejection, vascular thrombosis, and biliary complications. In order to avoid humoral rejection and improve graft survival, total plasma exchange in combination with an intense immunosuppressive regimen has been proposed to decrease hemagglutinin titers in ABO-I liver grafts. In some centers, this regimen was associated with splenectomy, phototherapy, and portal or arterial intrahepatic infusion therapy; however, as these patients are at high risk of sepsis, a selective approach using antigen-specific immunoadsorption with immunoadsorbent columns has been successfully proposed for ABO-I living donor kidney transplantation. Few cases have been reported following liver transplantation. We report our recent experience with three adult patients (two patients with acute liver failure, and one with severe cirrhosis and hepatic encephalopathy) transplanted in an emergency situation with an ABO-I liver graft and managed with the use of GlycoSorb ABO immunoadsorbent columns and a quadruple immunosuppressive regimen with preservation of the spleen. Eight sessions were performed in the three patients. Antigen-specific immunoadsorption greatly lowered the anti-A hemagglutinin titers. None of the three patients developed acute humoral or cellular rejection. Two patients are alive at 1.5 and 3 years follow-up with a normally functioning graft. The third patient died with a functioning graft, one month after the transplantation, from septic complications.

Antigen-specific Immunoadsorption of Anti-acetylcholine Receptor Antibodies from Sera of Patients with Myastenia Gravis

The binding of anti-acetylcholine receptor antibodies (AChRAb) to the main immunogenic region (MIR) of AChR alpha-subunit in the neuromuscular junction is the major pathogenesis of myasthenia gravis (MG). A synthetic peptide of 10 amino acids corresponding to the MIR of human AChR was coupled with cellulose beads to make an antigen-specific immunoadsorbent (hMIR10-CB). The hMIR10-CB could remove AChRAb in MG sera by 40.3+/-2.3%, compared to a tryptophan nonspecific adsorbent Trp-CB by only 22.4+/-1.5% as determined in ELISA, and also showed good blood compatibility for blood cells, plasma ions and plasma proteins as checked in whole blood perfusion in rabbits. The antigen-specific immunoadsorbent hMIR10-CB can serve as a potential candidate in the immunoadsorption treatment of MG.

Acute antibody-mediated rejection after ABO-incompatible kidney transplantation treated successfully with antigen-specific immunoadsorption

ABO-incompatible kidney transplantation is possible after pre-treatment with rituximab, intravenous immunoglobulin and basiliximab combined with tacrolimus, mycophenolate mofetil and prednisolone. We report on the first patient treated with this protocol who developed acute antibody-mediated rejection (Banff grade II with IgG deposits) caused by ABO antibodies (anti-B). Anti-rejection treatment with anti-B-specific immunoadsorption, intravenous immunoglobulin and methylprednisolone efficiently cleared deposited IgG from the kidney allograft and re-established normal kidney function. We suggest that ABO-incompatible kidney transplantation complicated by acute antibody-mediated rejection, caused by ABO antibodies, may successfully be treated with this regime.

Wiener Erfahrung mit ABO-inkompatibler Lebendnierentransplantation

ABO-incompatible kidney transplantation is a promising strategy for enlargement of living-donor pools. In recent years, recipient desensitization by blood group antigen-specific immunoadsorption, together with rituximab and intravenous immunoglobulin, has allowed excellent graft performance after ABO-incompatible transplantation. Adopting this protocol, originally described by Tydén and coworkers, we performed four living-donor renal transplants across the ABO barrier (A1-->0, A1-->B, B-->A1, A2-->0) between July 2007 and August 2008. Recipients were aged 25-66 years, donors 49-69 years. A protocol of on-demand immunoadsorption was followed, based on serial post-transplant antibody monitoring. Substantial and sustained decrease of blood group antibody levels was achieved in all four recipients, therefore post-transplant immunoadsorption was not needed. Graft and patient survival after 4-18 months' follow-up was 100%. Current serum creatinine was 1.3-2.0 mg/dl. Two grafts showed C4d deposits in peritubular capillaries in the complete absence of typical morphological features of antibody-mediated rejection. One recipient experienced early graft dysfunction, diagnosed as Banff borderline lesion, which responded well to steroid pulse therapy. The same recipient developed de novo interstitial fibrosis/tubular atrophy and arteriolar hyalinosis, presumably the result of suboptimal control of blood pressure and/or calcineurin inhibitor therapy. Two of the four recipients developed lymphoceles necessitating surgical revision. Apart from urinary tract infection in three patients and subclinical CMV in one, no major infectious complications were reported. Notably, two stable recipients developed polyoma BK viremia without clinical or morphological manifestations of polyomavirus-associated nephropathy. The results obtained in our small series support the earlier reported high efficiency of desensitization based on antigen-specific immunoadsorption. Nevertheless, the lack of long-term data will necessitate continuous and prudent consideration of the benefits and risks of this strategy.

ABO blood group-incompatible living donor kidney transplantation: a prospective, single-centre analysis including serial protocol biopsies

ABO incompatible kidney transplantation using antigen-specific immunoadsorption is increasingly performed but data on outcome, complications and protocol biopsies are still scarce. The present prospective single-centre study was aimed at these issues. This was a prospective single-centre cohort study of 10 successive ABO incompatible living donor kidney transplantations at the University Hospital Basel from September 2005 to October 2007. The following parameters were closely monitored during the whole follow-up: graft function, albuminuria, blood group antibody titres, CD19+ cell count, total IgG and IgG subclasses, CMV antigenaemia, decoy cells in the urine, EBV and polyoma BK virus PCR in the blood. Protocol biopsies were performed on Days 0 and 7 after 3, 6, 12 and 18 months. Patient and graft survival is 100% after a median follow-up of 489 days (range 183-916 days). Median serum creatinine is 137 micromol/l (range 70-215 micromol/l), and median urine albumin-creatinine ratio (UACR) is 3.1 mg/ mmol (range 0.6-7.8 mg/mmol) at the time of the last follow-up. All patients had sustained diminished CD19+ cell count and/or total IgG concentrations. Neither CMV antigenaemia nor EBV replication in the blood was observed. Seven patients had positive polyoma BK virus replication in the blood but none developed polyoma virus-associated nephropathy (PVAN). Protocol biopsies revealed rejection Banff IIa in three patients on Day 7, and in one patient after 3 and 6 months. Banff Ia rejection was found in five patients. All rejection episodes resolved. Mild signs of chronic antibody-mediated rejection were observed in five patients. ABO-incompatible kidney transplantation seems to be successful and safe. Modifications of the current protocol may be possible and may further reduce potential side effects and costs.

ABO-Incompatible Kidney Transplantation Using Antigen-Specific Immunoadsorption and Rituximab: A 3-Year Follow-up

In 2001 a protocol for ABO-incompatible (ABOi) kidney transplantation based on antigen-specific immunoadsorption and rituximab was introduced at our center, short-term results being comparable with those of ABO-compatible (ABOc) living donor kidney transplantation. Of greater importance, however, is long-term graft function, thus far not evaluated. The aim of this study was therefore to assess long-term results of this protocol. Twenty ABOi kidney recipients with more than 12-month follow-up were included in the study: all adult crossmatch negative ABOi kidney recipients (n=15) were compared with an adult ABOc living donor recipient control group (n=30), and all pediatric ABOi kidney recipients (<16 years of age) (n=5) were compared with a group of pediatric ABOc kidney recipients (n=18). Mean follow-up was three years. There was no significant difference in patient survival, nor in graft survival or in the incidence of acute rejection in any of the groups. In the adult kidney recipients mean glomerular filtration rate was equivalent at all time points (79-83 mL/min), as was Deltas-creatinine. In the pediatric groups, Deltas-creatinine was similar but glomerular filtration rate lower among the ABOi kidney recipients. There was a significant reduction (P<0.0001) without rebound in A/B antibody titers after transplantation (median IgG 1:2 and median IgM 1:1>1 year posttransplant) compared with pretransplant levels (median IgG 1:32 and IgM 1:16). We conclude that ABOi kidney transplantation using antigen-specific immunoadsorption and rituximab is equivalent to ABOc living donor kidney transplantation. ABOi transplantation after this protocol does not have a negative impact on long-term graft function.

Long-Term Results of ABO-Incompatible Kidney Transplantation With Antigen-Specific Immunoadsorption and Rituximab

ABO-incompatible (ABOi) kidney transplantation has gained a renewed interest during the past years. In 2001, a protocol for ABOi kidney transplantation based on antigen-specific immunoadsorption and rituximab was introduced at our center. In this study long-term graft function using this protocol was assessed. All ABOi kidney recipients with >1-year follow-up (n=15) were compared with all ABO-compatible (ABOc) living donor kidney recipients maintained on the same basic immunosuppression (n=27). Patient and graft survival as well as rejections and calculated glomerular filtration rate were analyzed. Mean follow-up was 3 years. There was no significant difference in patient and graft survival nor in rejection episodes. Mean glomerular filtration rate (79-83 ml/min) was equivalent at 1, 2, and 3 years in both groups. We conclude that ABOi kidney transplantation using antigen-specific immunoadsorption and rituximab is equivalent to standard ABOc living donor kidney transplantation. ABOi transplantation following this protocol does not have a negative impact on graft function long-term.

Preemptive Postoperative Antigen-Specific Immunoadsorption in ABO-Incompatible Kidney Transplantation: Necessary or Not?

Several standard protocols for ABO-incompatible kidney transplantation use scheduled preemptive antigen-specific immunoadsorption during the postoperative period. Our center has developed a different approach. Our patients undergo antigen-specific immunoadsorption postoperatively only if their isoagglutinine titers (immunoglobulin G anti-A/B) exceed 1:8 in the first postoperative week and 1:16 in the second postoperative week. Using this strategy, 22 ABO-incompatible kidney transplantations have been performed at our center since 2004. Only 32% of these patients (7 of 22) needed to undergo postoperative immunoadsorption (mean 4.1 immunoadsorption sessions per patient). The renal outcome in patients receiving postoperative immunoadsorption treatment versus the outcome in patients without postoperative immunoadsorption remained equal at a mean follow-up of 17 months. We identified a shorter pretransplant time on dialysis, a blood type constellation of donor A1/recipient O, and high initial starting titers as predictors for the need for postoperative immunoadsorption treatment. A more detailed version of this study, with modified tables and figures, has been accepted for publication in Nephrology Dialysis Transplantation.

The European Experience

A new protocol for ABO-incompatible kidney transplantation was introduced in 2001. In this protocol, antigen-specific immunoadsorption to remove existing AB antibodies is used in addition to rituximab to prevent rebound of antibodies and conventional immunosuppression (tacrolimus, mycophenolate mofetil, and prednisolone). This protocol has successively been implemented in many European centers, primarily in Sweden and Germany but also in the UK, Switzerland, the Netherlands, Norway, Denmark, Greece and Spain, and almost 200 ABO-incompatible transplantations have now been performed. In a recent 3-center pooled analysis of 60 consecutive ABO-incompatible living-donor transplantations, there were no graft losses that could be related to the ABO incompatibility and, when compared with ABO-compatible transplantations, no difference in graft or patient survival was found.

On-demand strategy as an alternative to conventionally scheduled post-transplant immunoadsorptions after ABO-incompatible kidney transplantation

Since 2001, approximately 100 ABO-incompatible kidney transplantations have been performed in Europe. The standard protocol, employed by most transplant centres, uses rituximab and scheduled pre-emptive antigen-specific immunoadsorption on post-operative days 3, 6 and 9. Our centre has performed 22 ABO-incompatible kidney transplantations since 2004, using a different approach; like in Sweden, all patients received immunoadsorptions preoperatively, but instead of scheduling pre-emptive post-transplant immunoadsorptions, we submitted patients to immunoadsorptions post-operatively only, if their isoagglutinine titers (IgG-Anti-A or -B) exceeded certain thresholds. These thresholds were greater than 1 : 8 in the first post-operative week and greater than 1 : 16 in the second post-operative week, respectively. A shorter pre-operative length on dialysis, a blood-type constellation of donor A1/recipient 0 and 9a high initial starting-titer were identified as predictors for post-operative immunoadsorptions. Using this on-demand strategy, our data reveal that a titer-dependent protocol reduces costs at no additional risk for the patient.

Implementation of a Protocol for ABO-Incompatible Kidney Transplantation – A Three-Center Experience With 60 Consecutive Transplantations

A new protocol for ABO-incompatible kidney transplantation has recently been introduced. We report here on the joint experience of the implementation in Stockholm and Uppsala, Sweden and Freiburg, Germany. The new protocol utilizes antigen-specific immunoadsorption to remove existing ABO-antibodies, rituximab, and intravenous immunoglobulin to prevent the rebound of antibodies, and conventional tacrolimus, mycophenolate-mofetil, and prednisolone immunosuppression. Sixty consecutive ABO-incompatible kidney transplantations were included in the study. The outcome is compared with the results of 274 ABO-compatible live donor transplantations performed during the same period. Two of the ABO-incompatible grafts have been lost (non-compliance and death with functioning graft). All the remaining 58 grafts had good renal function at a follow-up of up to 61 months. We did not observe any late rebound of antibodies and there were no humoral rejections. Graft survival was 97% for the ABO-incompatible compared with 95% for the ABO-compatible. Patient survival was 98% in both groups. There was a significant variation in preoperative A/B-antibody titer between the centers, with a median 1:8 in Uppsala, median 1:32 in Stockholm and median 1:128 in Freiburg. More preoperative antibody adsorptions were therefore needed in Freiburg than in Stockholm and Uppsala. The new protocol was easily implemented and there were no graft losses that could be related to ABO-incompatibility. A significant inter-institutional variation in the measurement of anti-AB-antibodies was found, having a substantial impact on the number of immunoadsorptions and consequently on the total cost for the procedure. A standardized fluorescence-activated cell sorting technique for antibody quantification is much needed.

ABO‐incompatible kidney transplantation—Proposal of an intensified apheresis strategy for patients with high initial isoagglutinine titers

Since Tydén's description of ABO-incompatible (ABOi) kidney transplantations based on antigen-specific immunoadsorption (IA) and rituximab (Tydén et al., Am J Transplant 2005;5:145-148), this technique has been successfully adopted by many transplant centers worldwide. The majority of centers strictly adhere to the Swedish protocol and perform IAs with a target volume of 1.5-2 plasma volumes on preoperative days -6, -5, -2, and -1, and postoperative days +3, +6, and +9, respectively. Patients who initially present with an IgG anti-A/B titer higher than 1:128 are not considered suitable candidates for ABOi transplantation by the Swedish protocol. Our center has gone beyond these suggestions and follows a slightly different strategy: We do not exclude patients with initial IgG anti-A/B titers higher than 1:128 and we perform as many preoperative antigen-specific extracorporeal treatments as needed to reach a threshold isoagglutinine titer of 1:4 or less. To intensify isoagglutinine clearance preoperatively, the total target volume per treatment was increased to 2.5-3 plasma volumes. Preconditioning IAs are performed every other day, instead of daily. Postoperatively we perform IAs only, if titers mandate us to do so (Wilpert et al., Nephrol Dial Transplant 2007;22:3048-3051). We report on 11 "high-titer patients" who entered our ABOi kidney transplant program with initial titers of 1:256 or above. Seven of 11 patients (64%) could successfully be transplanted with our modified ABO-apheresis protocol. Four of 11 high-titer patients did not reach target isoagglutinine titers of 1:4 or less and therefore did not undergo transplantation. We conclude that intensified preoperative IA renders a majority of high-titer patients suitable candidates for ABOi kidney transplantation.