C4d-positive acute humoral renal allograft rejection: effective treatment by immunoadsorption

Therapeutic apheresis in renal transplantation: An update

Therapeutic apheresis (TA) plays a significant role in various aspects of renal transplantation. It has been a necessary preconditioning component in ABO incompatible kidney transplants and an important modality in the removal of anti-human leukocyte antigen (HLA) antibodies both in the context of desensitization protocols that have been developed to allow highly sensitized kidney transplant candidates to be successfully transplanted and as treatment of antibody mediated rejection episodes post transplantation. In addition, TA has been used with various results for the management of recurrent focal segmental glomerulosclerosis. The purpose of this review is to examine the evidence supporting the application of TA as an adjunctive therapeutic option to immunosuppressive agents in protocols both before and after kidney transplantation.

WITHDRAWN:Therapeutic apheresis in renal transplantation: An update

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.transci.2023.103844 of original article. The duplicate article has therefore been withdrawn. This error bears no reflection on the article or its authors. The publisher apologizes to the authors and the readers for this unfortunate error. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/policies/article-withdrawal

On a Long and Winding Road: Alloantibodies in Organ Transplantation

Today we know that both the humoral and the cellular arm of the immune system are engaged in severe immunological challenges. A close interaction between B and T cells can be observed in most "natural" challenges, including infections, malignancies, and autoimmune diseases. The importance and power of humoral immunity are impressively demonstrated by the current coronavirus disease 2019 pandemic. Organ transplant rejection is a normal immune response to a completely "artificial" challenge. It took a long time before the multifaceted action of different immunological forces was recognized and a unified, generally accepted opinion could be formed. Here, we address prominent paradigms and paradigm shifts in the field of transplantation immunology. We identify several instances in which the transplant community missed a timely paradigm shift because essential, available knowledge was ignored. Moreover, we discuss key findings that critically contributed to our understanding of transplant immunology but sometimes developed with delay and in a roundabout way, as was the case with antibody-mediated rejection-a main focus of this article. These include the discovery of the molecular principles of histocompatibility, the recognition of the microcirculation as a key interface of immune damage, the refinement of alloantibody detection, the description of C4d as a footmark of endothelium-bound antibody, and last but not least, the developments in biopsy-based diagnostics beyond conventional morphology, which only now give us a glimpse of the enormous complexity and pathogenetic diversity of rejection.

Efficacy of Combined Desensitization Therapy Based on Protein A Immunoadsorption on Anti-human Leukocyte Antigen Antibodies in Sensitized Kidney Transplant Recipients: A Retrospective Study

Background and objectives

Protein A immunoadsorption (PA-IA) therapy is an immunoglobulin selective apheresis for pre-transplantation desensitization therapy and treatment of post-transplantation antibody-mediated rejection. There is no unified protocol for the timing of PA-IA therapy or its combination with other drug therapy. This study aimed to investigate and analyze the clearance effects of desensitization therapy on human leukocyte antigen (HLA) antibodies to provide a reference for the formulation of clinical desensitization therapy regimens.

Materials and methods

Overall, 27 kidney transplant recipients who received preoperative/postoperative desensitization therapy based on PA-IA therapy in combination with drug therapy were enrolled. The pre-treatment mean fluorescence intensity (MFI) of 1324 human leukocyte antigen (HLA) antibody specificities (MFI >2000) and the post-treatment MFI of the corresponding antibody specificities (after one, four, seven, and 10 sessions) were recorded to analyze the changes in antibody level reduction for the different antibody classes and MFI ranges.

Results

After 10 sessions of PA-IA therapy, the MFI of class I antibodies decreased from 8298.56 to 3196.15 (reduction of 66.80%), while the MFI of class II antibodies decreased from 13,521.09 to 2773.29 (reduction of 71.14%). The pre-treatment level of class II antibodies was significantly higher than that of class I antibodies (p<0.001), whereas the post-treatment levels of class I and II antibodies were comparable (p>0.05). The clearance effects of PA-IA therapy were greater for strongly positive (MFI>10,000) class II antibodies than for strongly positive class I antibodies, showing a reduction of 62.59% (25.17% to 91.04%) and 45.13% (32.70% to 73.94%), respectively (p=0.015).

Conclusions

We confirmed the removal efficacy of PA-IA for HLA antibodies. The removal efficacy of class II antibodies on PA-IA is not inferior to that of class I. Under an adequate number of treatment sessions, the clearance effect of PA-IA therapy for strongly positive class II antibodies may be greater than that for strongly positive class I antibodies.

Desensitization Regimen Consisting of High-Dose Intravenous Immunoglobulin, Plasmapheresis, and Rituximab (an Anti-CD20 Antibody), Without Eculizumab and/or Bortezomib, in 41 Highly Sensitized Kidney Transplant Recipients

OBJECTIVES

Antibody-mediated rejection in patients with positive crossmatches can be severe and result in sudden onset of oliguria, leading to graft loss. In an attempt to prevent posttransplant oliguria, we adopted a preoperative desensitization protocol involving the use of high-dose intravenous immunoglobulin/plasmapheresis and the anti-CD20 antibody, rituximab, in 41 transplant recipients with positive crossmatch test results.

MATERIALS AND METHODS

We retrospectively examined the clinical courses of the 41 kidney transplant recipients, paying special attention to renal graft function, urine volume, and changes in the titers of donor-specific antibodies.

RESULTS

Four grafts were lost during an average of 4.5-year follow-up. Average graft function was excellent, with a serum creatinine level of 1.3 ± 0.4 mg/dL. Sufficient urine output, with no oliguria or anuria, was achieved postoperatively in 40 of the 41 patients. However, among the 34 patients who underwent graft biopsies, the biopsies revealed acute antibody-mediated rejection in 21 patients (62%), and chronic antibodymediated rejection in 10 patients (30%).

CONCLUSIONS

The high-dose intravenous immunoglobulin treatment included in our desensitization protocol was shown to be safe and effective for achieving successful transplant outcomes and allowed the avoidance of more aggressive B-cell-targeted treatments, such as C5 inhibitors and/or proteosome inhibitors, for preventing posttransplant oliguria and anuria.

Performance, clinical effectiveness, and safety of immunoadsorption in a wide range of indications

Immunoadsorption is well known to selectively remove immunoglobulins and immune complexes from plasma and is applied in a variety of autoimmune diseases and for desensitization before, or at acute rejection after organ transplantation. Performance, safety, and clinical effectiveness of immunoadsorption were the aim of this study. This prospective, noninterventional, multicentre cohort study included patients treated with immunoadsorption (Immunosorba or GLOBAFFIN adsorbers) for any indication. Clinical effectiveness was assessed after termination of the patient's individual treatment schedule. Eighty‐one patients were included, 69 were treated with Immunosorba, 11 with GLOBAFFIN, one patient with both adsorbers. A majority of patients was treated for neurological indications, dilated cardiomyopathy, and before or after kidney or heart transplantation. Mean IgG reduction from pre‐ to post‐treatment was 69.9% ± 11.5% for Immunosorba and 74.1% ± 5.0% for GLOBAFFIN, respectively. The overall IgG reduction over a complete treatment block was 68%–93% with Immunosorba and 62%–90% with GLOBAFFIN depending on the duration of the overall treatment. After termination of the immunoadsorption therapy, an improvement of clinical status was observed in 63.0%, stabilization of symptoms in 29.6%, and a deterioration in 4.9% of patients. Changes in fibrinogen, thrombocytes, and albumin were mostly classified as noncritical. Overall, the treatments were well tolerated. Immunoadsorption in routine clinical practice with both GLOBAFFIN and Immunosorba has been safely performed, was well tolerated by patients, and effective in lowering immunoglobulins with an improvement or maintenance of clinical status, thus represents an additional therapeutic option for therapy refractory immune disorders.

Efficacy of plasmapheresis and semi-selective immunoadsorption for removal of anti-HLA antibodies

BACKGROUND

In organ transplantation, apheresis is frequently used for removal of anti-HLA antibodies. However, it is unclear whether plasmapheresis (PP) or semi-selective immunoadsorption (IA) should be employed, and the optimal number of apheresis sessions required to reach post-treatment objectives is also unknown.

METHODS

We enrolled 43 patients from Bordeaux University Hospital who were treated with PP (n = 29) or IA (n = 14) for antibody-mediated rejection or pre-transplant desensitization. Using Luminex single-antigen flow beads, we assessed the initial mean fluorescence intensity (MFI) of 1416 positive beads with MFIs obtained after 7 to 8 apheresis sessions (extended protocol) and, if a serum was available, after the first four sessions (short protocol).

RESULTS

MFI reduction after extended apheresis protocol was stronger with IA [87% (61%-100%)] than with PP [73% (22%-100%)] (P < .001). Indeed, 59% of the beads had a final MFI < 2000 with IA, whereas only 38% with PP (P < .001). The efficacy of removal depended on initial MFI but not on HLA specificity. A short protocol of apheresis showed excellent results without superiority of IA over PP for antibodies with an initial MFI < 3000. For antibodies showing MFI ≥2000 after four sessions, the residual MFI predicted the effectiveness of four additional sessions.

CONCLUSION

Monitoring the MFI of anti-HLA antibodies before and during apheresis protocol can guide physicians in the selection of apheresis technique and the number of sessions to be performed.

Resultados de la inmnuadsorción en el trasplante ABOi y el rechazo humoral en una unidad de hemodiáilsis hospitalaria

INTRODUCCIÓN El tratamiento con inmunoadsorción no selectiva fue introducido en nuestra unidad de hemodiálisis hospitalaria con el objetivo de permitir la desensibilización previa a un trasplante renal con incompatibilidad de grupo sanguíneo y el tratamiento del rechazo mediado por anticuerpos. OBJETIVO Analizar los resultados de la técnica de inmunoadsorción no selectiva, en una unidad de hemodiálisis hospitalaria. MATERIAL Y MÉTODOS Estudio retrospectivo, descriptivo, de los primeros 18 pacientes tratados en nuestro centro con inmunoadsorción no selectiva (años 2012-2017) en las indicaciones de acondicionamiento del trasplante ABOi y tratamiento del rechazo humoral. RESULTADOS Durante un periodo de 5 años se analizaron un total de 128 sesiones de inmunoadsorción no selectiva. El 38,9% (n=7) de los casos para desensibilización previa al trasplante renal con incompatibilidad de grupo sanguíneo y el 61,1% (n=11) restante para el tratamiento del rechazo mediado por anticuerpos. En el primer caso, realizaron una media de 8±0,6 sesiones de inmunoadsorción previas al trasplante renal y el 57,1% se complementaron 2 sesiones posteriores. El tratamiento concomitante fue el protocolizado con Rituximab e inmunoglobulinas, requiriendo el 57,1% la realización de recambios plasmáticos. En el segundo caso, realizaron una media de 5,9±2 sesiones de inmunoadsorción. El tratamiento concomitante fue el mismo y el 27,3% realizaron recambios plasmáticos. CONCLUSIONES El trasplante renal de donante vivo ABOi tras la desensibilización fue posible en el 100% de los pacientes. El 72,7% de los pacientes tratados para el rechazo mediado por anticuerpos mantienen actualmente la funcionalidad del injerto.

Association Between Cytokines and Their Receptor Antagonist Gene Polymorphisms and Clinical Risk Factors and Acute Rejection Following Renal Transplantation

BACKGROUND Acute rejection (AR) after renal transplantation affects both patient and graft survival. There is growing evidence of the genetic association between cytokine or its receptor antagonist and AR in solid organ transplantation. The objectives of this study were to investigate the role of recipient TNF β, IL-10, IL-1β, and IL-1 receptor antagonist (ra) gene polymorphism, as well as traditional clinical variables such as panel-reactive antibody (PRA) levels, donor type, and HLA mismatches in AR following renal transplantation. MATERIAL AND METHODS TNF β (+252A/G), IL-10 (-592A/C), IL-1β (-511C/T) and IL-1ra (86 bp VNTR) gene polymorphisms were determined in 195 renal allograft recipients with and without AR, using PCR. Both these genotypic variants and clinical risk factors were investigated for correlation with AR within the first year after renal transplantation. RESULTS Patients with increased pre-transplant PRA levels (P<0.001) and donor type (P=0.012) were prone to the development of AR. After adjusting for all variables of P<0.2, a PRA level >10% (OR=4.515, 95% confidence intervals=1.738-11.727, P=0.002) and the receipt of a graft from a donation after cardiac death (DCD) donor (OR=2.437, 95% confidence intervals=1.047-5.673, P=0.039) remained significantly associated with AR in a multivariate logistic regression analysis. No correlation could be found between recipients with an episode and absence of acute rejection and the gene polymorphisms of these cytokines investigated in the present study. CONCLUSIONS This study shows that the presence of increased pre-transplant levels of PRA and the receipt of a graft from DCD donor other than cytokine gene polymorphisms are significant risk factors for AR in renal transplantation. To reduce the occurrence of AR, clinicians should take necessary measures to lower the PRA levels and pay more attention to patients who received a graft from a DCD donor.

Mannose-binding lectin-2 and ficolin-2 gene polymorphisms and clinical risk factors for acute rejection in kidney transplantation

INTRODUCTION

There is growing evidence that the lectin pathway is significantly associated with acute rejection. Rare studies associated both gene polymorphisms of MBL2 and FCN2 with acute rejection after kidney transplantation. The aim of the present study was to investigate the role of the lectin gene profile and clinical risk factors such as PRA level on acute rejection in kidney transplant recipients.

METHODS

We prospectively analyzed 157 kidney transplant recipients with and without acute rejection. A total of 6 well-known functional single-nucleotide polymorphisms in the MBL2 gene and 5 in the FCN2 gene of the recipients were determined by gene sequencing. MBL2 and FCN2 genotypic variants were analyzed for association with the incidence of acute rejection within the first year after kidney transplantation.

RESULTS

After adjusting for variables of P<0.2, we found the differences in the incidence of acute rejection were only according to panel-reactive antibodies (odds ratios (OR) = 6.468, 95% confidence intervals (CI)= 2.017-20.740, P = 0.002) and the HH genotypes of MBL2 promoter -550 (OR = 2.448, 95%CI = 1.026-5.839, P = 0.044).

CONCLUSION

Panel-reactive antibodies and the HH genotypes of MBL2 promoter -550 have significant impacts on the risk of developing acute rejection after kidney transplantation.

The diagnostic value of transcription factors T-bet/GATA3 ratio in predicting antibody-mediated rejection

Background. Previous data showed that the predominance of intraglomerular T-bet or GATA3 is correlated with different mechanisms of rejection, suggesting that the ratio of T-bet/GATA3 might be used to distinguish antibody-mediated rejection (ABMR) and T-cell-mediated rejection (TCMR). Methods. We compared the intraglomerular T-bet/GATA3 ratio in ABMR and TCMR. The intragraft expression of T-bet and GATA3 was studied via immunohistochemistry. The correlation of the diagnosis of AMR with the ratio of T-bet/GATA3 was examined. Results. Both intraglomerular T-bet- and GATA3-expressing cells were increased during acute rejection. T-bet/GATA3>1 was strongly correlated with ABMR (93.3% versus 18.2%). The incidence of positive HLA-I/II antibodies and glomerulitis is significantly higher in T-bet/GATA3>1 group (P < 0.001, 0.013, resp.). The scores of peritubular capillary inflammation and glomerulitis were also higher in T-bet/GATA3>1 group (P = 0.052, P < 0.001, resp.). Nevertheless, T-bet/GATA3>1 is also correlated with C4d-negative ABMR and resistance to steroid treatment. Compared with C4d deposition, T-bet/GATA3>1 had a slight lower (90% versus 100%) specificity but a much higher (87.5% versus 68.8%) sensitivity. Conclusion. Our data suggested that intraglomerular predominance of T-bet over GATA3 might be used as diagnosis maker of ABMR in addition to C4d, especially in C4d-negative cases.

Late and chronic antibody-mediated rejection: main barrier to long term graft survival

Antibody-mediated rejection (AMR) is an important cause of graft loss after organ transplantation. It is caused by anti-donor-specific antibodies especially anti-HLA antibodies. C4d had been regarded as a diagnosis marker for AMR. Although most early AMR episodes can be successfully controlled or reversed, late and chronic AMR remains the leading cause of late graft loss. The strategies which work in early AMR have limited effect on late/chronic episodes. Here, we reviewed the lines of evidence that late/chronic AMR is the leading cause of late graft loss, characteristics of late AMR, and current strategies in managing late/chronic AMR. More effort should be put on the management of late/chronic AMR to make a better long term graft survival.

Peritubular capillaritis in early renal allograft dysfunction is an indicator of acute rejection

BACKGROUND

Kidneys showing acute rejection (AR) processes often are accompanied by various levels of peritubular capillaritis (Ptc), especially cases of acute humoral rejection (AHR). However, it is not known whether the presence of Ptc alone is sufficient evidence of allograft rejection. This study was performed to determine the diagnostic value of Ptc as a marker for AR among cases of early renal allograft dysfunction.

METHODS

Fifty-three AR showed C4d deposition in the peritubular capillaries (PTCs; C4d+AR group), 50 AR were without C4d deposition (C4d-AR group), 30 had Ptc alone (Ptc group), 28 had acute tubular necrosis (ATN group), and 78 were surveillance biopsies (control group).

RESULTS

Analyzing the immunophenotype of infiltrating T lymphocytes and serum antibodies, discovered that 85.9% of control biopsies presented with a regulatory phenotype. Among the Ptc cohort, 93.3% of biopsies showed the cytotoxic phenotype with no significant different between C4d+AR and C4d-AR (96.2% vs 92.0%). We also observed the prevalence of panel-reactive antibody (PRA) and major-histocompatibility-complex class I chain-related gene A (MICA) antibodies to be increased among Ptc (30.0% and 43.3%, respectively), albeit not significantly different from C4d+AR (49.1% and 39.6%, respectively). The prevalences were low in other groups.

CONCLUSIONS

These results implied that Ptc in biopsy specimens from patients with early renal allograft dysfunction was an indicator of AR, especially AHR.

Humoral immunity is involved in the development of pericentral fibrosis after pediatric live donor liver transplantation

Although LT can be successful for treating end-stage liver disease in children, some patients develop fibrosis around the central vein area (PCF). This raises the possibility that PCF could lead to later cirrhosis and graft failure. Here, we report a retrospective immunohistochemical study of 28 patients who received a live donor liver transplant. We assessed the incidence and etiology of PCF using CD3, CD20, HLA-DR, and C4d-specific antibodies. Histological evidence of PCF was found in 13 cases (46.4%), of which 11 (84.6%) had experienced ACR and/or CP events post-transplant. Immunohistochemical evaluation revealed significantly stronger staining with these antibodies in the central vein area in PCF, especially for CD20 and C4d. This implies humoral immunopathology and suggests involvement of humoral immunity in the development of PCF. These results further imply that suppression of cellular immunity alone is insufficient to prevent PCF. We therefore suggest that suppression of both humoral and cellular immunity in combination would be required for prevention of PCF.

Improving survival during heart transplantation: diagnosis of antibody-mediated rejection and techniques for the prevention of graft injury

The diagnosis of antibody-mediated rejection (AMR) has presented a challenge due to the pleiomorphic immunologic responses that represent the condition. A consensus with regard to its pathological diagnosis continues to evolve. Due to an increasing number of sensitized patients undergoing heart transplantation, its incidence appears to be on the rise and the condition is associated with worse outcomes than acute cellular rejection. Treatment of AMR is also more difficult and response to increases in conventional immunosuppression is often limited. Risk factors for AMR include the use of ventricular assist devices, prior exposure to blood products, allografts and multiparity. Detection of alloantibodies with a high specificity and sensitivity allows risk stratification of recipients at potential risk of AMR. Desensitization and AMR treatment strategies are focused on several therapeutic targets, including suppression of T and B cells and elimination or inhibition of circulating antibodies.

ABO-incompatible kidney transplantation using regenerative selective immunoglobulin adsorption

BACKGROUND

ABO-incompatible (ABOi) kidney transplantation is an established procedure relying on the removal of donor-specific isoagglutinine antibodies as part of the recipient preconditioning. At present, current protocols using immunoadsorption apply a single-use selective carbohydrate isoagglutinine adsorber. A regenerative and selective immunoglobulin immunoadsorption could be an alternative but has not been reported for ABOi transplantation.

METHODS

Eight patients were treated with the commonly used isoagglutinine carbohydrate epitope adsorber and seven with a regenerative polyclonal sheep anti-immunoglobulin adsorber as part of the preconditioning for ABOi kidney transplantation. An IgG-isoagglutinine titer of less or equal 1:4 qualified for transplantation. Treatment safety, efficiency, length of desensitization, number of postoperative immunoadsorptions, and allograft outcome were retrospectively compared.

RESULTS

With the use of the immunoglobulin adsorber the median initial isoagglutinine IgG titers of 1:64 (range 1:32-1:256) were lowered to the target of 1:4 preoperatively with a mean of 6.2 immunoadsorptions (range 5-11). Mean IgG/IgM titer step reduction per IA was 1.98/1.21 for (range 0-4/0-4) and mean titer step rebound 1.31/0.82 (range 0-4/0-3), respectively. The number of immunoadsorptions and length of desensitization was not different from the use of the specific isoagglutinine adsorbers. After transplantation, no rejection occurred and only one postoperative immunoadsorption was necessary. No adverse events in relation to immunoadsorption were observed. Graft function was comparable to the isoagglutinine adsorber group.

CONCLUSION

These data suggest that ABOi kidney transplantation can be performed safely and effectively with a selective regenerative immunoglobulin immunoadsorber.

Prevention and treatment of alloantibody-mediated kidney transplant rejection

Antibody-mediated rejection (AMR), which is commonly caused by preformed and/or de novo HLA alloantibodies, has evolved as a leading cause of early and late kidney allograft injury. In recent years, effective treatment strategies have been established to counteract the deleterious effects of humoral alloreactivity. One major therapeutic challenge is the barrier of a positive pretransplant lymphocytotoxic crossmatch. Several apheresis- and/or IVIG-based protocols have been shown to enable successful crossmatch conversion, including a strategy of peritransplant immunoadsorption for rapid crossmatch conversion immediately before deceased donor transplantation. While such protocols may increase transplant rates and allow for acceptable graft survival, at least in the short-term, it has become evident that, despite intense treatment, many patients still experience clinical or subclinical AMR. This reinforces the need for innovative strategies, such as complementary allocation programs to improve transplant outcomes. For acute AMR, various studies have suggested efficiency of plasmapheresis- or immunoadsorption-based protocols. There is, however, no established treatment for chronic AMR and the development of strategies to reverse or at least halt chronic active rejection remains a big challenge. Major improvements can be expected from studies evaluating innovative therapeutic concepts, such as proteasome inhibition or complement blocking agents.

Antibody-mediated rejection in kidney transplantation: an update

INTRODUCTION

Acute antibody-mediated rejection (AMR) in renal-transplant recipients is generally less responsive to conventional antirejection therapy and has a worse prognosis than acute cellular rejection.

AREAS COVERED

This review provides a broad understanding of the pathogenesis of AMR, recent advances in its therapy, and future directions. Conventional therapeutic approaches to AMR have minimal impact on mature plasma cells, the major source of antibody production. Emerging therapies include bortezomib, a proteasome inhibitor, and eculizumab, an anti-C5 antibody. In several reports, bortezomib therapy resulted in prompt reversal of rejection, decreased titers of donor-specific antibodies (DSA), and improved renal allograft function. Eculizumab also reversed AMR and prevented its development in patients with high post-transplantation DSA levels.

EXPERT OPINION

Despite the small sample size and lack of controls, these studies are encouraging, and although larger studies and long-term follow-up are needed, bortezomib and eculizumab may play a major future role in AMR therapy.

Bortezomib: a new player in pre- and post-transplant desensitization?

Several desensitization strategies have been investigated for the reversal of acute antibody-mediated rejection or for the removal of preformed anti-HLA antibodies, with the aim to promote access to renal transplantation. Today, their success appears limited or incomplete. Bortezomib, a selective inhibitor of the 26S proteasome, which is largely used in the treatment of multiple myeloma, could be a novel promising desensitizing agent. Its mechanism of action and preliminary clinical use in renal transplantation is reviewed here.

Peritransplant immunoadsorption for positive crossmatch deceased donor kidney transplantation

Various desensitization protocols were shown to enable successful living donor kidney transplantation across a positive complement-dependent cytotoxicity crossmatch (CDCXM). Positive crossmatch transplantation, however, is less well established for deceased donor transplantation. We report a cohort of 68 deceased donor renal allograft recipients who, on the basis of broad sensitization (lymphocytotoxic panel reactivity ≥40%), were subjected to a protocol of peritransplant immunoadsorption (IA). Treatment consisted of a single session of immediate pretransplant IA (protein A) followed by posttransplant IA and antilymphocyte antibody therapy. Twenty-one patients had a positive CDCXM, which could be rendered negative by pretransplant apheresis. Solid phase HLA antibody detection revealed preformed donor-specific antibodies (DSA) in all 21 CDCXM-positive and in 30 CDCXM-negative recipients. At 5 years, overall graft survival, death-censored graft survival and patient survival were 63%, 76% and 87%, respectively, without any differences between CDCXM-positive, CDCXM-negative/DSA-positive and CDCXM-negative/DSA-negative recipients. Furthermore, groups did not differ regarding rates of antibody-mediated rejection (24% vs. 30% vs. 24%, p = 0.84), cellular rejection (14% vs. 23% vs. 18%, p = 0.7) or allograft function (median 5-year serum creatinine: 1.3 vs. 1.8 vs. 1.7 mg/dL, p = 0.62). Our results suggest that peritransplant IA is an effective strategy for rapid desensitization in deceased donor transplantation.

Antibody-mediated rejection: treatment alternatives and outcomes

Over the past 10 years, thanks to the development of sensitive methods of antibody detection and markers of antibody injury such as C4d staining, the role of anti-human leukocyte antigen (HLA) and non-HLA alloantibodies as effectors of acute and chronic immune allograft injury has been revisited. Antibody-mediated rejection (AMR) defines all allograft rejection caused by antibodies directed against donor-specific HLA molecules, blood group antigen (ABO)-isoagglutinins, or endothelial cell antigens. Antibody-mediated rejection can be a recalcitrant process, resistant to therapy and carries an ominous prognosis to the graft. In concordance with these views, treatment protocols for AMR use permutations of a multiple-prong approach that include (1) the suppression of the T-cell dependent antibody response, (2) the removal of donor reactive antibody, (3) the blockade of the residual alloantibody, and (4) the depletion of naive and memory B-cells. Although all published protocols report a variable rate of success, a major weakness of all current protocols is the lack of effective anti-plasma cell agents. In comparison to acute AMR, the treatment for chronic AMR (CAMR) is not well characterized. Although in acute AMR large titers of pre-existent alloantibodies result in massive activation of the complement system and lytic injury of the graft endothelium, thereby requiring aggressive and fast removal of the offending agents, in CAMR, complement activation results in sublytic endothelial cell injury and activation. Although this type of injury results in chronic graft failure, its slow progression likely renders it amenable of suppression by heightening of maintenance immunosuppression and anti-idiotypic blockade of the circulating alloantibody without the need of plasma exchange. In this review, we will discuss the rationale behind the design of treatment protocols for acute AMR and CAMR as well as their reported results and complications.

Present techniques for antibody removal

Renal transplantation into a patient with a positive cytotoxic cross-match or with an incompatible blood group inevitably results in acute humoral rejection, unless the HLA or anti-A/B antibodies have been removed before transplantation. Although there are several procedures to remove HLA and anti-A/B antibodies, plasmapheresis and immunoadsorption are the most commonly used. In this report, presently available techniques for antibody removal are briefly reviewed.

Antibody-mediated rejection of the kidney after simultaneous pancreas-kidney transplantation

The prevalence, risk factors, and outcome of antibody-mediated rejection (AMR) of the kidney after simultaneous pancreas-kidney transplantation are unknown. In 136 simultaneous pancreas-kidney recipients who were followed for an average of 3.1 yr, 21 episodes of AMR of the kidney allograft were identified. Eight episodes occurred early (</=90 d) after transplantation, and 13 occurred later. Histologic evidence of concomitant acute cellular rejection was noted in 12 cases; the other nine had evidence only of humoral rejection. In 13 cases, clinical rejection of the pancreas was diagnosed simultaneously, and two of these were biopsy proven and were positive for C4d immunostaining. Multivariate analysis identified only one significant risk factor: Female patients were three times more likely to experience AMR. Nearly all early episodes resolved with treatment and did not predict graft loss, but multivariate Cox models revealed that late AMR episodes more than tripled the risk for kidney and pancreas graft loss; therefore, new strategies are needed to prevent and to treat late AMR in simultaneous pancreas-kidney transplant recipients.

Histological Markers of Humoral Rejection in Renal Transplant Patients

Diagnosis of "suspicious humoral rejection" can be formulated in the presence of peritubular capillary (PTC) C4d deposition and one of the following tissue changes: (1) acute tubular necrosis, (2) glomerulitis or presence of polymophonuclear leukocytes or monocytes in PTC, or (3) arteritis. From January 2004 to October 2006, we performed immunohistochemical staining with anti-C4d antibody on 54 renal biopsies from 39 renal transplant patients. In 25 biopsies we observed diffuse (n = 13) or focal (n = 12) C4d deposition. Based on C4d-positivity, patients were divided into three groups: group 1 included 19 C4d-negative patients; group 2, 10 patients with diffuse C4d-positivity; and group 3, 10 patients with focal C4d-positivity. Panel-reaction antibody-positive tests were associated with diffuse C4d-positivity: 50% of group 2 patients showed a positive test, while no group 1 or 3 patients had a positive test (P < .001). Glomerulitis was observed in six biopsies and associated with diffuse C4d staining. Graft loss occurred in 3/10 group 2 patients (30%); 2/19 group 1 patients (10.5%), and 1/10 group 3 patients (10%). Viral infections were experienced in the year of the biopsy by 50% of group 1 patients 80% of group 2 patients, and 100% of group 3 patients (P < .025), indicating a significantly greater number of infections among patients with C4d-positive biopsies. In eight cases, anti-thymocyte globulin was administered less than 21 days before the biopsy: four had diffuse and four had focal C4d positivity.

Antibody-Mediated Rejection

The introduction of both complement 4d (C4d) staining in renal allograft biopsies and sensitive methods to detect anti-human leukocyte antigen antibodies, such as single antigen bead flow assays, into tissue-typing techniques have shown the importance of antibody-mediated alloimmune response in kidney transplantation. The use of these sensitive methods, combined with the increased number of transplants in highly sensitized patients with donor-specific antibodies, or patients receiving desensitization protocols, have increased the awareness and thus the incidence of acute antibody-mediated rejection. Chronic rejection also can be mediated through alloantibodies, and the term chronic antibody-mediated rejection recently was proposed. In this review article we summarize the current knowledge of the role of alloantibodies in transplantation, the diagnosis and treatment of acute and chronic antibody-mediated rejection, and their effect on graft function and outcome.

Immunoadsorption of Alloantibodies onto Erythroid Membrane Antigens Encapsulated into Polymeric Microparticles

PURPOSE

Classical immunoadsorbents used for the removal of deleterious molecules in blood such as auto-antibodies are prepared by covalent coupling of antigens onto previously chemically activated supports. Such a chemical treatment may induce a potential toxicity which can be reduced if new immunoadsorbents are prepared by encapsulating erythrocytes-ghosts carrying antigens inside polymeric and porous microparticles.

MATERIALS AND METHODS

Erythrocyte-ghosts obtained by hemolysis in hypotonic buffer were encapsulated into ethylcellulose microparticles by w/o/w emulsification. The porosity of microparticles was evaluated by mercury porosimetry. The adsorption ability of encapsulated antigens was evaluated by hemagglutination after contact in tube or elution in column with polyclonal antibody solutions or human blood-plasma.

RESULTS

The encapsulation process did not significantly alter the evaluated antigens since a significant decrease in anti-A (from 256 to 4) as well as anti-Kell (from 64 to 2) antibody titer has been observed in column after eight chromatographic runs (2 h). The higher the ghost concentration (total protein content of 6 mg/ml), the higher the adsorption capacity.

CONCLUSION

Encapsulation, currently used for drug delivery purposes, may consequently also be applied to the design of new immunoadsorbents as biomaterials.

Peritubular capillary C4d deposition and renal outcome in post-transplant IgA nephropathy

BACKGROUND

Immunological staining of the transplanted kidney for C4d in peritubular capillaries (C4d(PTC)) has emerged as a useful method to detect antibody-mediated rejection in situ. In this retrospective study, we evaluated the prevalence of C4d(PTC) deposition in allograft renal biopsies diagnosed of IgA nephropathy (IgAN) and analysed its clinical significance.

METHOD

Sixty-six biopsy specimens of post-transplant IgAN, which were obtained to evaluate azotemia and/or heavy proteinuria, were examined by immunohistochemical staining of the paraffin sections with polyclonal antibody for C4d.

RESULTS

C4d was stained positively in peritubular capillaries in 16 (24%) of the 66 cases. The C4d(PTC)-negative (n=50) and C4d(PTC)-positive groups (n=16) were not different in recipient gender, age, donor age, type of donor (living vs. cadaveric), interval from transplantation to graft biopsy (41.6+/- 21.8 vs. 48.3+/-26.1 months) and post-biopsy follow-up period (60.3+/-23.3 vs. 56.9+/-25.4 months). During the follow-up period, 12 of 50 (24%) although the incidence of graft failure was not different by the C4d deposition in peritubular capillaries, intervals from renal biopsy to graft failure tended to be shorter in C4d(PTC)-positive cases than C4d(PTC)-negative cases. In Kaplan-Meier analysis, the renal allograft function of the C4d(PTC)-positive group deteriorated more rapidly than that of the C4d(PTC)-negative group (p<0.05). Histologically, the C4d(PTC)-positive group had findings suggestive of acute cellular rejection more commonly than the C4d(PTC)-negative group (p<0.01).

CONCLUSIONS

Evidence of humoral rejection, as demonstrated by C4d(PTC) deposition, was concurrently present in significant portions of post-transplant IgAN biopsy specimens and was associated with more rapid deterioration of renal function. These results suggest that C4d(PTC) positivity needs to be determined at the time of biopsy even in cases of post-transplant glomerulonephritis and immunosuppression may need to be modified accordingly.

New treatments for acute humoral rejection of kidney allografts

Acute antibody-mediated rejection (acute humoral rejection; AHR) of organ allografts usually presents as severe dysfunction with a high risk of allograft loss. Peritubular capillary complement C4d deposition with renal dysfunction, associated with circulating donor-specific anti-human leukocyte antigen alloantibodies, is diagnostic of AHR in kidney allografts. Removal of alloantibodies with suppression of antibody production and rejection reversal is now possible. Therapeutic strategies that include combinations of plasmapheresis (or immunoadsorption), tacrolimus, mycophenolate mofetil and/or intravenous immunoglobulins, as well as rituximab or splenectomy, have been recently used to successfully treat AHR. However, the optimal protocol to treat AHR still remains to be defined. Anti-CD20+ monoclonal antibody therapy (rituximab) aiming at depleting B cells and suppressing antibody production has been used as rescue therapy in some episodes of steroid- and antilymphocyte-resistant humoral rejection. Plasmapheresis and/or intravenous polyclonal immunoglobulin, as well as rituximab, have also been used to successfully desensitize selected high-immunological risk patients in anticipation of a previously cross-match positive (or ABO incompatible) kidney transplantation. In the near future, the possible role of new specific anti-B-cell approaches or, possibly, of new anti-T-cell activation approaches using selective agents such as belatacept should be assessed to further refine the present treatment of humoral rejection.

Successful Management of Antibody-Mediated Cardiac Allograft Rejection With Combined Immunoadsorption and Anti-CD20 Monoclonal Antibody Treatment: Case Report and Literature Review

Chronic rejection is still the major limitation of long-term outcome of heart transplant recipients. Several recent studies demonstrated that a not negligible proportion of chronic allograft rejection episodes are not only mediated by T-cell response but also triggered by pre-transplant and de novo post-transplant donor-specific alloantibodies. This points at a fundamental role of humoral immune response mechanisms that contribute to early and late graft failure. This type of rejection is an unsolved problem solid organ transplantation because current immunosuppressive regimens are generally intended to interfere in T-cell signalling pathways. Various options for the removal of circulating alloantibodies and the prevention of alloantibody formation by B-cell depletion have been described. Nevertheless, effective standardized schemes for the treatment of antibody-mediated graft rejection have to be defined. We present a heart transplant recipient with sustained antibody-mediated graft rejection who was successfully managed with a combination treatment consisting of 3 cycles of immunoadsorption and a single-dose administration of the anti-CD20 monoclonal antibody rituximab.

The utility of splenectomy as rescue treatment for severe acute antibody mediated rejection

Antibody-mediated rejection (AMR) after desensitization for a positive crossmatch (+XM) live donor renal transplant can be severe and result in sudden onset oliguria and loss of the allograft. Attempts to rescue these kidneys using plasmapheresis (PP) and IVIg may be ineffective due to the magnitude of antibody burden that must be controlled to prevent renal thrombosis or cortical necrosis. We review our experience using splenectomy combined with PP/IVIg as rescue therapy for patients experiencing an acute deterioration in renal function and a rise in donor-specific antibody within the first posttransplant week after desensitization for a +XM. Five patients underwent immediate splenectomy followed by PP/IVIg and had return of allograft function within 48 h of the procedure. Emergent splenectomy followed by PP/IVIg may be an effective treatment for reversing severe AMR.

A Nonsurgical Technique for Blood Access in Extracorporeal Affinity Adsorption of Antibodies in Rats

Monoclonal antibodies for targeting cytotoxic conjugates to tumor cells are currently being evaluated together with extracorporeal affinity adsorption. The aim of the adsorption was to reduce undesired side effects in normal organs and to increase the tumor-to-normal tissue ratios. This technique is also applicable to several other therapeutic areas such as immune-mediated disorders, that is, autoimmunity, allergy, and transplantation rejection. We describe an improved technique for extracorporeal affinity adsorption of radiolabeled biotinylated antibodies in rats. Blood access is established through the tail artery and tail vein, without surgical insertion of permanent catheters. This technique is simple, does not require surgery, and causes only minimal stress to the animals. In addition, experiments can be carried out on several animals simultaneously. This new technique is of considerable benefit for studying extracorporeal affinity adsorption in rats, as experiments can be carried out with negligible anatomical and physiological interventions, compared to previously used techniques.

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

This study analyzes the incidence and course of antibody-mediated rejection (AMR) in a cohort of 237 renal transplant patients followed for 30 +/- 20 months. Among these, 32 patients were considered to be at risk for AMR and received intravenous immunoglobulin (IVIg), either as preconditioning (Group A, n = 18) or at the time of transplant (Group B, n = 14). The prevalence of AMR was 27.8% in Group A, 57.1% in Group B and 3.9% in the remainder of the population. Although graft loss remains greater among AMR than for acute cellular rejection (ACR) or the overall transplant population, we have identified a good outcome group (GFR > 15 mL/min/1.73 m(2)) (n = 13), whose renal function at the end of follow-up was comparable to that of the general transplant population. The factors associated with bad outcome are: (1) immunologic: presence and/or persistence of donor-specific anti-HLA antibodies post-transplantation and (2) histologic: neutrophilic glomerulitis, peritubular capillary dilatation with neutrophil infiltrates and interstitial edema at the time of first biopsy; and at the time of late biopsy (3-6 months): lesions of vascular rejection, and monocyte/macrophage infiltrates in glomeruli and dilated peritubular capillaries. Persistence of C4d does not predict outcome. This study outlines for the first time the immunologic and histologic profiles of AMR patients with poor prognosis.

Subclinical acute antibody-mediated rejection in positive crossmatch renal allografts

Subclinical antibody-mediated rejection (AMR) has been described in renal allograft recipients with stable serum creatinine (SCr), however whether this leads to development of chronic allograft nephropathy (CAN) remains unknown. We retrospectively reviewed data from 83 patients who received HLA-incompatible renal allografts following desensitization to remove donor-specific antibodies (DSA). Ten patients had an allograft biopsy showing subclinical AMR [stable SCr, neutrophil margination in peritubular capillaries (PTC), diffuse PTC C4d, positive DSA] during the first year post-transplantation; 3 patients were treated with plasmapheresis and intravenous immunoglobulin. Three patients had a subsequent rise in SCr and an associated biopsy with AMR; 5 others showed diagnostic or possible subclinical AMR on a later protocol biopsy. One graft was lost, while remaining patients have normal or mildly elevated SCr 8-45 months post-transplantation. However, the mean increase in CAN score (cg + ci + ct + cv) from those biopsies showing subclinical AMR to follow-up biopsies 335 +/- 248 (SD) days later was significantly greater (3.5 +/- 2.5 versus 1.0 +/- 2.0, p = 0.01) than that in 24 recipients of HLA-incompatible grafts with no AMR over a similar interval (360 +/- 117 days), suggesting that subclinical AMR may contribute to development of CAN.

Immunoadsorption in severe C4d-positive acute kidney allograft rejection: a randomized controlled trial

Antibody-mediated rejection (AMR) frequently causes refractory graft dysfunction. This randomized controlled trial was designed to evaluate whether immunoadsorption (IA) is effective in the treatment of severe C4d-positive AMR. Ten out of 756 kidney allograft recipients were included. Patients were randomly assigned to IA with protein A (N = 5) or no such treatment (N = 5) with the option of IA rescue after 3 weeks. Enrolled recipients were subjected to tacrolimus conversion and, if indicated, 'anti-cellular' treatment. All IA-treated patients responded to treatment. One death unrelated to IA occurred after successful reversal of rejection. Four control subjects remained dialysis-dependent. With the exception of one patient who developed graft necrosis, non-responders were subjected to rescue IA, however, without success. Because of a high graft loss rate in the control group the study was terminated after a first interim analysis. Even though limited by small patient numbers, this trial suggests efficiency of IA in reversing severe AMR.

Treatment of early mixed cellular and humoral renal allograft rejection with tacrolimus and mycophenolate mofetil

This prospective study investigated the efficiency of the tacrolimus (Tac) combined with mycophenolate mofetil (MMF) alone without immunoadsorption (IA) or plasmapheresis (PPH) as treatment for early (within 2 weeks) acute humoral rejection (AHR) in non-sensitized renal allograft recipients. Of 160 patients enrolled in this prospective study, 11 patients had histologically and clinically confirmed early steroid-resistant acute rejection with an antibody response and received Tac-MMF therapy. No other aggressive rescue methods such as IA, PPH were used, according to the study design. Patients (n=11) were followed for 13.8+/-3.5 months; nine were females. The complement-dependent cytotoxicity crossmatch was negative before transplantation in all patients and only positive for panel-reactive antibody in one patient. Most of the rejection episodes were mixed with cellular rejection (four patients met Banff IIA criteria, five patients met Banff IIB, one patient met Banff IB, and one patient met Banff borderline). After 16.19+/-6.16 days of treatment, all rejection episodes were successfully reversed and all graft functions were stable, with a mean serum creatinine level of 1.12+/-0.32 mg/dl during follow-up. No patient suffered from severe infectious complications (except one case of urinary infection). Our investigation suggests that Tac combined with MMF alone is adequate to reverse early mixed cellular and humoral C4d-positive rejection in non-sensitized renal allograft recipients.

Significance of C4d deposition in the diagnosis of rejection after liver transplantation

C4d immunohistochemical staining of liver allograft biopsies was performed to assess its relationship to other pathological changes in the liver. C4d deposition was detected in 69.2% of liver graft biopsies from patients under going rejection, 33.3% of liver graft biopsies from patients with hepatitis B relapse after transplantation, and 28.6% of liver biopsies from patients with hepatitis B. When rejection occurred C4d deposition was located in the vascular walls of portal areas and hepatic sinusoidal walls. Examination of biopsies from patients with hepatitis B relapse after transplantation or hepatitis B infection showed C4d deposition only in the vascular walls of the portal area. C4d deposition in both vascular walls of portal area and hepatic sinusoidal walls was detected in only one of 12 ischemia-reperfusion damage cases. Repeated biopsy of the same patient 1 month later revealed acute cellular rejection. No C4d deposition was found in biopsies from a patient with bile duct occlusion after liver transplantation. C4d might serve as a sensitive marker for the diagnosis of liver rejection.