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

Therapy in the Course of Kidney Graft Rejection-Implications for the Cardiovascular System-A Systematic Review

Kidney graft failure is not a homogenous disease and the Banff classification distinguishes several types of graft rejection. The maintenance of a transplant and the treatment of its failure require specific medications and differ due to the underlying molecular mechanism. As a consequence, patients suffering from different rejection types will experience distinct side-effects upon therapy. The review is focused on comparing treatment regimens as well as presenting the latest insights into innovative therapeutic approaches in patients with an ongoing active ABMR, chronic active ABMR, chronic ABMR, acute TCMR, chronic active TCMR, borderline and mixed rejection. Furthermore, the profile of cardiovascular adverse effects in relation to the applied therapy was subjected to scrutiny. Lastly, a detailed assessment and comparison of different approaches were conducted in order to identify those that are the most and least detrimental for patients suffering from kidney graft failure.

Acute Antibody-mediated Rejection Coexisting With T Cell-mediated Rejection in Pediatric ABO-incompatible Transplantation

The management and outcome of ABO-incompatible (ABO-I) liver transplantation (LT) has been improving over the past few decades. Recently, the introduction of a pathological evaluation of acute antibody-mediated rejection (AMR) for liver allograft has provided a new recognition of allograft rejection in LT.

Methods

One hundred and one pediatric ABO-I LTs performed in our institute were retrospectively analyzed. We assessed the clinical manifestations, diagnosis, and treatment of acute AMR, focusing on the recipient age and pathological findings.

Results

Twelve cases (11.9%) of acute AMR related to ABO-I were observed. Nine cases developed mixed T cell-mediated rejection (TCMR)/AMR. These consisted of 6 patients in the younger age group for whom the preconditioning treatment was not indicated and 4 patients in the older age group to whom rituximab was administered as planned. Two patients in the older age group to whom preoperative rituximab was not administered as planned developed isolated AMR. Acute AMR in the older group required plasma exchange for treatment, regardless of the coexistence of TCMR. In contrast, those in the younger group were successfully treated by intravenous methylprednisolone pulse and intravenous immunoglobulin without plasma exchange, accounting for mild immune reaction.

Conclusions

Acute ABO-I AMR can develop simultaneously with TCMR, even in young patients with a compromised humoral immune response following ABO-I LT. Establishing the accurate diagnosis of AMR with a pathological examination, including component 4d staining, is crucial for optimizing treatment.

Extracellular Vesicles Mediate Immune Responses to Tissue-Associated Self-Antigens: Role in Solid Organ Transplantations

Transplantation is a treatment option for patients diagnosed with end-stage organ diseases; however, long-term graft survival is affected by rejection of the transplanted organ by immune and nonimmune responses. Several studies have demonstrated that both acute and chronic rejection can occur after transplantation of kidney, heart, and lungs. A strong correlation has been reported between de novo synthesis of donor-specific antibodies (HLA-DSAs) and development of both acute and chronic rejection; however, some transplant recipients with chronic rejection do not have detectable HLA-DSAs. Studies of sera from such patients demonstrate that immune responses to tissue-associated antigens (TaAgs) may also play an important role in the development of chronic rejection, either alone or in combination with HLA-DSAs. The synergistic effect between HLA-DSAs and antibodies to TaAgs is being established, but the underlying mechanism is yet to be defined. We hypothesize that HLA-DSAs damage the transplanted donor organ resulting in stress and leading to the release of extracellular vesicles, which contribute to chronic rejection. These vesicles express both donor human leukocyte antigen (HLA) and non-HLA TaAgs, which can activate antigen-presenting cells and lead to immune responses and development of antibodies to both donor HLA and non-HLA tissue-associated Ags. Extracellular vesicles (EVs) are released by cells under many circumstances due to both physiological and pathological conditions. Primarily employing clinical specimens obtained from human lung transplant recipients undergoing acute or chronic rejection, our group has demonstrated that circulating extracellular vesicles display both mismatched donor HLA molecules and lung-associated Ags (collagen-V and K-alpha 1 tubulin). This review focuses on recent studies demonstrating an important role of antibodies to tissue-associated Ags in the rejection of transplanted organs, particularly chronic rejection. We will also discuss the important role of extracellular vesicles released from transplanted organs in cross-talk between alloimmunity and autoimmunity to tissue-associated Ags after solid organ transplantation.

Mouse Model Established by Early Renal Transplantation After Skin Allograft Sensitization Mimics Clinical Antibody-Mediated Rejection

Antibody-mediated rejection (AMR) is the main barrier to renal graft survival, and mouse renal AMR models are important to study this process. Current mouse models are established by priming the recipient to donor skin for over 7 days before kidney transplantation. The robustness of AMR in these cases is too strong to mimic clinical AMR and it is unclear why altering the priming times ranging from 7 to 91 days fails to reduce the AMR potency in these models. In the present study, we found that the donor-recipient combination and skin graft size were determinants of donor-specific antibody (DSA) development patterns after skin transplantation. DSA-IgG was sustained for over 100 days after skin challenge, accounting for an identical AMR robustness upon different skin priming times over 7 days. However, decreasing the skin priming time within 7 days attenuated the robustness of subsequent renal allograft AMR in C3H to Balb/c mice. Four-day skin priming guaranteed that recipients develop acute renal AMR mixed with a high ratio of graft-infiltrating macrophages, renal grafts survived for a mean of 6.4 ± 2.1 days, characterized by typical AMR histological changes, such as glomerulitis, peritubular capillary (PTC) dilation, and capillaritis, deposition of IgG and C3d in PTCs, but less prevalence of microthrombus, whereas the cellular rejection histological change of tubulitis was absent to mild. With this scheme, we also found that the renal AMR model can be developed using common mouse strains such as C57BL/6 and Balb/c, with mean prolonged renal graft survival times of 14.4 ± 5.0 days. Finally, we proved that donor-matched skin challenge after kidney transplantation did not strongly affect DSA development and kidney graft outcome. These findings may facilitate an understanding and establishment of mouse renal allograft AMR models and promote AMR-associated studies.

Renal association clinical practice guideline in post-operative care in the kidney transplant recipient

These guidelines cover the care of patients from the period following kidney transplantation until the transplant is no longer working or the patient dies. During the early phase prevention of acute rejection and infection are the priority. After around 3-6 months, the priorities change to preservation of transplant function and avoiding the long-term complications of immunosuppressive medication (the medication used to suppress the immune system to prevent rejection). The topics discussed include organization of outpatient follow up, immunosuppressive medication, treatment of acute and chronic rejection, and prevention of complications. The potential complications discussed include heart disease, infection, cancer, bone disease and blood disorders. There is also a section on contraception and reproductive issues.Immediately after the introduction there is a statement of all the recommendations. These recommendations are written in a language that we think should be understandable by many patients, relatives, carers and other interested people. Consequently we have not reworded or restated them in this lay summary. They are graded 1 or 2 depending on the strength of the recommendation by the authors, and AD depending on the quality of the evidence that the recommendation is based on.

Maintenance immunosuppressants in the management of antibody-mediated renal allograft rejection: which regimen is best?

Antibody-mediated rejection (AMR) is a pivotal cause of long-term graft failure following renal transplantation. De novo donor-specific antibody reduction is essential to prevent AMR and improve long-term graft survival in renal transplant recipients. Although the number of early AMR episodes can be successfully controlled by attenuating de novo donor-specific antibodies, the long-term outcomes are unsatisfactory. Numerous studies have focused on new strategies to reverse AMR, but the available evidence suggests that maintenance immunosuppressive agents play important roles. This article reviews data on the use of various maintenance immunosuppressive strategies in the management of AMR, with a focus on antibody-mediated kidney transplant rejection. Its aim is to help provide options benefitting long-term graft survival in renal transplant recipients.

Mechanisms of antibody-mediated acute and chronic rejection of kidney allografts

PURPOSE OF REVIEW

Antibody-mediated rejection is responsible for up to half of acute rejection episodes in kidney transplant patients and more than half of late graft failures. Antibodies cause acute graft abnormalities that are distinct from T cell-mediated rejection and at later times posttransplant, a distinct pathologic lesion is associated with capillary basement membrane multilayering and glomerulopathy. Despite the importance of donor-reactive antibodies as the leading cause of kidney graft failure, mechanisms underlying antibody-mediated acute and chronic kidney graft injury are poorly understood. Here, we review recent insights provided from clinical studies as well as from animal models that may help to identify new targets for therapy.

RECENT FINDINGS

Studies of biopsies from kidney grafts in patients with donor-specific antibody versus those without have utilized analysis of pathologic lesions and gene expression to identify the distinct characteristics of antibody-mediated rejection. These analyses have indicated the presence of natural killer cells and their activation during antibody-mediated rejection. The impact of studies of antibody-mediated allograft injury in animal models have lagged behind these clinical studies, but have been useful in testing the activation of innate immune components within allografts in the presence of donor-specific antibodies.

SUMMARY

Most insights into processes of antibody-mediated rejection of kidney grafts have come from carefully designed clinical studies. However, several new mouse models of antibody-mediated kidney allograft rejection may replicate the abnormalities observed in clinical kidney grafts and may be useful in directly testing mechanisms that underlie acute and chronic antibody-mediated graft injury.

Natural killer cells play a critical role in mediating inflammation and graft failure during antibody-mediated rejection of kidney allografts

While the incidence of antibody-mediated kidney graft rejection has increased, the key cellular and molecular participants underlying this graft injury remain unclear. Rejection of kidney allografts in mice lacking the chemokine receptor CCR5 is dependent on production of donor-specific antibody. Here we determine if cells expressing cytotoxic function contributed to antibody-mediated kidney allograft rejection in these recipients. Wild-type C57BL/6, B6.CCR5(-/-), and B6.CD8(-/-)/CCR5(-/-) mice were transplanted with complete MHC-mismatched A/J kidney grafts, and intragraft inflammatory components were followed to rejection. B6.CCR5(-/-) and B6.CD8(-/-)/CCR5(-/-) recipients rejected kidney allografts by day 35, whereas 65% of allografts in wild-type recipients survived past day 80 post-transplant. Rejected allografts in wild-type C57BL/6, B6.CCR5(-/-), and B6.CD8(-/-)/CCR5(-/-) recipients expressed high levels of VCAM-1 and MMP7 mRNA that was associated with high serum titers of donor-specific antibody. High levels of perforin and granzyme B mRNA expression peaked on day 6 post-transplant in allografts in all recipients, but were absent in isografts. Depletion of natural killer cells in B6.CD8(-/-)/CCR5(-/-) recipients reduced this expression to background levels and promoted the long-term survival of 40% of the kidney allografts. Thus, natural killer cells have a role in increased inflammation during antibody-mediated kidney allograft injury and in rejection of the grafts.

Advances in pharmacotherapy to treat kidney transplant rejection

INTRODUCTION

Current immunosuppressive combination therapy provides excellent prevention of T-cell-mediated rejection following renal transplantation; however, antibody-mediated rejection remains of high concern and accounts for a large number of long-term allograft losses. The recent development of protocol biopsies resulted in the definition of subclinical rejection (SCR), showing histologic evidence for rejection but unremarkable clinical course.

AREAS COVERED

This review describes the current knowledge and evidence of pharmacotherapy to treat kidney allograft rejections and covers SCR treatment options. Each substance is analyzed with regard to its classical indication and further discussed for the treatment of other forms of rejection.

EXPERT OPINION

Despite a lack of randomized trials, early acute T-cell-mediated rejection can be treated effectively in most cases without graft loss. The necessity to treat SCR is currently unclear. Due to a lack of effective therapies, new treatment approaches for antibody-mediated rejection are an urgent medical need to improve long-term outcomes. Future research should aim to better define pathophysiology and histology, stratify risk, and develop rational treatment strategies from randomized controlled trials, in order to establish the value of novel therapies in the arsenal of rejection pharmacotherapy. However, the effective prevention of rejection with minimal side effects still remains the goal in immunosuppression.

Novel CD8 T cell alloreactivities in CCR5-deficient recipients of class II MHC disparate kidney grafts

Recipient CD4 T regulatory cells inhibit the acute T cell-mediated rejection of renal allografts in wild-type mice. The survival of single class II MHC-disparate H-2(bm12) renal allografts was tested in B6.CCR5(-/-) recipients, which have defects in T regulatory cell activities that constrain alloimmune responses. In contrast to wild-type C57BL/6 recipients, B6.CCR5(-/-) recipients rejected the bm12 renal allografts. However, donor-reactive CD8 T cells rather than CD4 T cells were the primary effector T cells mediating rejection. The CD8 T cells induced to bm12 allografts in CCR5-deficient recipients were reactive to peptides spanning the 3 aa difference in the I-A(bm12) versus I-A(b) β-chains presented by K(b) and D(b) class I MHC molecules. Allograft-primed CD8 T cells from CCR5-deficient allograft recipients were activated during culture either with proinflammatory cytokine-stimulated wild-type endothelial cells pulsed with the I-A(bm12) peptides or with proinflammatory cytokine-simulated bm12 endothelial cells, indicating their presentation of the I-A(bm12) β-chain peptide/class I MHC complexes. In addition to induction by bm12 renal allografts, the I-A(bm12) β-chain-reactive CD8 T cells were induced in CCR5-deficient, but not wild-type C57BL/6, mice by immunization with the peptides. These results reveal novel alloreactive CD8 T cell specificities in CCR5-deficient recipients of single class II MHC renal allografts that mediate rejection of the allografts.

Using individual DSA titers to assess for accommodation after late humoral rejection

Management of late humoral rejection remains challenging, and DSA may persist. A case report illustrates how individual DSA titers using solid-phase-based assays may help to assess for accommodation. A male cystinosis patient received a cadaveric renal transplant at the age of 12 yr with a daclizumab, tacrolimus, MMF, and steroids-based immunosuppression. After three acute rejection episodes over the first eight months, interstitial fibrosis/tubular atrophy (IF/TA) was diagnosed on biopsy, while the immunosuppression was left unchanged with a high target exposure for both tacrolimus and MPA. One yr later, AMR type III (C4d and DSA positive) was treated with daily plasmapheresis, IVIG 100 mg/kg and pulse steroids 5 mg/kg. DSA (DR 53, DQ4, and DQ 2) were not responding until the plasma volume was increased to 2.5 plasma volumes. A second rise of creatinine confirmed worse humoral rejection; daily plasma exchange was resumed, and two doses of rituximab (375 mg/m(2)) were given. Subsequently, all DSA dropped, but only DR53 DSA remained unchanged, whereas the DQ antibodies rebounded to very strong titers. With a follow-up of over 120 days after recovery of the CD19 count, off all additional treatment and on identical immunosuppression with tacrolimus and MMF and prednisone, the patient's creatinine remained stable between 45 and 50 um while DQ DSA remain strong to very strong. We conclude that the patient is in a state of accommodation. DSA titers should be monitored when managing late humoral rejection.

Key role for CD4 T cells during mixed antibody-mediated rejection of renal allografts

We utilized mouse models to elucidate the immunologic mechanisms of functional graft loss during mixed antibody-mediated rejection of renal allografts (mixed AMR), in which humoral and cellular responses to the graft occur concomitantly. Although the majority of T cells in the graft at the time of rejection were CD8 T cells with only a minor population of CD4 T cells, depletion of CD4 but not CD8 cells prevented acute graft loss during mixed AMR. CD4 depletion eliminated antidonor alloantibodies and conferred protection from destruction of renal allografts. ELISPOT revealed that CD4 T effectors responded to donor alloantigens by both the direct and indirect pathways of allorecognition. In transfer studies, CD4 T effectors primed to donor alloantigens were highly effective at promoting acute graft dysfunction, and exhibited the attributes of effector T cells. Laser capture microdissection and confirmatory immunostaining studies revealed that CD4 T cells infiltrating the graft produced effector molecules with graft destructive potential. Bioluminescent imaging confirmed that CD4 T effectors traffic to the graft site in immune replete hosts. These data document that host CD4 T cells can promote acute dysfunction of renal allografts by directly mediating graft injury in addition to facilitating antidonor alloantibody responses.

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.

Effects of sotrastaurin, mycophenolic acid and everolimus on human B-lymphocyte function and activation

Humoral rejection processes may lead to allograft injury and subsequent dysfunction. Today, only one B-cell-specific agent is in clinical use and the effects of standard and new immunosuppressant substances on B-cell activation and function are not fully clarified. The impact of sotrastaurin, mycophenolic acid and everolimus on human B-lymphocyte function was assessed by analysing proliferation, apoptosis, CD80/CD86 expression and immunoglobulin and IL-10 production in primary stimulated B cells. In addition, B-cell co-cultures with pre-activated T cells were performed to evaluate the effect of the different immunosuppressive agents on T-cell-dependent immunoglobulin production. Sotrastaurin did not inhibit B-cell proliferation, CD80/CD86 expression, and IgG production and had only minor effects on IgM levels at the highest concentration administered. In contrast, mycophenolic acid and everolimus had strong effects on all B-cell functions in a dose-dependent manner. All immunosuppressive agents caused decreased immunoglobulin levels in T-cell-dependent B-cell cultures. The data provided here suggest that mycophenolic acid and everolimus, but not sotrastaurin, are potent inhibitors of human B-lymphocyte function and activation.

Evaluation of vascular lesions using circulating endothelial cells in renal transplant patients

Objective: To investigate the correlation between circulating endothelial cells (CECs) and vascular lesions in renal allografts.

Methodology: Sixty-two renal transplant patients were divided into four groups according to biopsy data. CECs were isolated from peripheral blood with anti-CD136-coated immunomagnetic Dynabeads and counted by microscopy during biopsy. CEC numbers were compared in each group, as well as the correlation between CECs and C4d and vascular changes in different groups.

Result: CECs counts were higher in the acute rejection (AR) with endarteritis group than in the normal group (p < 0.01), acute tubular necrosis (ATN) group (p < 0.01) and chronic allograft nephropathy (CAN) group (p < 0.01), there were no difference among ATN, normal and CAN) group (p = 0.587). There was no difference among the normal group without hyaline, normal group with hyaline and CAN with hyaline group. An increasing CECs count was related to C4d-positive AR (p = 0.008; κ score = 0.519) and infiltration of inflammatory cells (p = 0.002, κ score = 0.573) in proximal tubule cells (PTCs). The CECs count decreased after intensive therapy in five patients (p = 0.001).

Conclusion: Elevation of the CEC count in blood was related to endarteritis. Elevation of CEC count was related to C4d deposition and infiltration of inflammatory cells in PTCs.

Steroid-resistant acute allograft rejection in renal transplantation

Steroid-resistant rejection after pediatric renal transplantation forms a rare but severe complication with a guarded prognosis particularly if this occurs late after transplantation. There is a paucity of data on how to manage these challenging rejection episodes, particularly in the pediatric literature. Mohan Shenoy et al. published a case series of 15 patients who were treated with anti-thymocyte globulin for steroid-resistant acute allograft rejection over a 15-year period in a single center in this issue of Pediatric Nephrology. While the results for the early rejection group were encouraging, the results in the eight patients with late rejection episodes after transplantation were unfavorable and afflicted with a high incidence of side-effects. Important diagnostic tools such as C4d staining of the renal transplant biopsy and the measurement of donor-specific antibodies were underutilized. The editorial reviews the importance of the differentiation between humoral and cellular rejection and the challenges of treating late antibody-mediated acute rejection in these patients. A multi-center approach is required to establish a registry of these events and ideally prospective randomized interventions should be designed to provide some evidence base for the management of this challenging complication after pediatric renal transplantation.

Epidemiology and management of refractory lupus nephritis

Although the survival of patients with lupus nephritis (LN) has improved considerably in recent years, refractory LN appears in a substantial proportion of patients and, therefore, treatment of LN remains a real challenge today. We will use the term "refractory" LN, for those cases with none or partial response to first-line therapies. In this sense, numerous epidemiological factors, including racial, socioeconomic, histological and serological parameters, may influence treatment response and, therefore, may have an impact on the outcome of renal involvement. Initial conventional therapy will depend somewhat on these epidemiological factors. If this initial therapy fails, fortunately today we have alternative therapies that include the multitarget therapy and the use of biologics. Published evidence about these therapies is presented in this review. Important terms in the management of LN, such as the definition of complete response, partial response, sustained response and renal flare as well as the discrimination of different types of flare, are also discussed here according to the European consensus statement on the terminology used in the management of lupus glomerulonephritis.

Predominance of intraglomerular T-bet or GATA3 may determine mechanism of transplant rejection

The transcription factors T-bet and GATA3 determine the differentiation of helper T cells into Th1 or Th2 cells, respectively. An altered ratio of their relative expression promotes the pathogenesis of certain immunological diseases, but whether this may also contribute to the pathogenesis of antibody-mediated rejection (ABMR) versus T cell-mediated rejection (TCMR) is unknown. Here, we characterized the intragraft expression of T-bet and GATA3 and determined the correlation of their levels with the presence of typical lesions of ABMR and TCMR. We found a predominant intraglomerular expression of T-bet in patients with ABMR, which was distinct from that in patients with TCMR. In ABMR, interstitial T-bet expression was typically located in peritubular capillaries, although the overall quantity of interstitial T-bet was less than that observed in TCMR. The expression of intraglomerular T-bet correlated with infiltration of CD4+ and CD8+ lymphocytes, which express T-bet, as well as intraglomerular CD68+ monocyte/macrophages, which do not express T-bet. The predominance of intraglomerular T-bet expression relative to GATA3 expression associated with poor response to treatment with bolus steroid. In summary, predominance of intraglomerular T-bet expression correlates with antibody-mediated rejection and resistance to steroid treatment.

De novo development of circulating anti-endothelial cell antibodies rather than pre-existing antibodies is associated with post-transplant allograft rejection

Anti-endothelial cell antibodies (AECAs) are thought to be involved in the development of renal allograft rejection. To explore this further, we determine whether AECAs play a role both in predicting the incidence of allograft rejection and long-term outcomes by analysis of serum samples from 226 renal allograft recipients for AECAs pre- and post-transplant. Surprisingly, the presence of pre-existing AECAs was not associated with either an increased risk of rejection or a detrimental impact on recipient/graft survival. Subsequent de novo AECAs, however, were associated with a significantly increased risk of early acute rejection. Moreover, these rejections tended to be more severe with a significantly increased incidence of both steroid-resistant and multiple episodes of acute rejection. The acute rejections associated with de novo AECAs did not correlate with C4d deposition at the time of renal biopsy, but did demonstrate an association with the presence of glomerulitis and peritubular capillary inflammation. Significantly more patients with de novo AECAs developed graft dysfunction. Thus, our prospective study suggests the emergence of de novo AECAs is associated with transplant rejection that may lead to allograft dysfunction.

Late acute kidney transplant rejection: clinicopathological correlates and response to corticosteroid therapy

Acute rejection is a major cause of kidney allograft dysfunction. It is important to distinguish between cellular and antibody-mediated rejection to guide the treatment strategy. The management of acute antibody-mediated rejection includes aggressive therapy with plasmapheresis and intravenous immunoglobulin. C4d staining of peritubular capillaries has emerged as a valuable tool in identifying antibody-mediated rejection. Late acute rejection has a worse prognosis than early acute rejection. The clinical and pathological features of late acute kidney allograft rejection are not fully understood. We studied the clinicopathological correlates of late acute rejection in our patient population. During an 8-year period, all patients who had late acute rejection (6 months posttransplant) were identified. Patients with severe chronic changes and transplant glomerulopathy were excluded. Patients were divided into C4d+ and C4d- groups [corrected]. Histopathological features and treatment response were evaluated. Nine patients met inclusion criteria (4 C4d+, 5 C4d-). Maintenance therapy consisted of mycophenolate mofetil, calcineurin inhibitors, and low-dose prednisone. All patients received intravenous methlyprednisolone or high-dose oral prednisone as antirejection therapy. Seventy-five percent of patients in the C4d+ group and 80% of patients in the C4d- group had a clinical response to antirejection therapy. The majority of C4d+ patients with late acute rejection who were treated with corticosteroids alone responded to treatment. The study raises the possibility that a subset of C4d+ patients with acute rejection who do not have severe chronic changes might respond to corticosteroid therapy alone.

Clinical relevance of pretransplant human leukocyte antigen donor-specific antibodies in renal patients waiting for a transplant: a risk factor

The use of highly sensitive solid-phase antibody detection assays, including x-MAP multiple bead-based technology (Luminex), has greatly enhanced our ability to accurately detect and define very low levels of HLA antibodies. These developments have led to patients having increasing lists of antibody specificities (which may not be clinically relevant), resulting in a new "technological barrier" to transplantation in sensitized patients. Alloantibodies play a major role in all types of solid organ rejection; the presence of low-titer donor-specific antigen (DSA) identified pretransplant is associated with an increased risk of antibody-mediated rejection (AMR). However, these low-titer antibodies do not represent an absolute contraindication to transplant. Improvement in the diagnosis and treatment of AMR will allow sensitized patients with DSA to be successfully transplanted in the short term, but extended follow-up is required to ensure acceptable long-term graft survival in this group. These factors must be integrated into the decision algorithms for immunosuppressive treatment in patients at immunologic risk.

Successful renal re-transplantation in the presence of pre-existing anti-DQ5 antibodies when there was zero mismatch at class I human leukocyte antigen A, B, & C: a case report

Introduction

Hyperacute rejection may be prevented by avoiding the transplantation of kidneys into patients with pre-existing anti-donor Class I human leukocyte antigen antibodies. However, the role of anti-donor-Class II-human leukocyte antigen-DQ antibodies is not established. The question is ever more relevant as more sensitive cross-matching techniques detect many additional antibodies during the final crossmatch. We now report successful renal transplantation of a patient who had pre-existing antibodies against his donor's human leukocyte antigen-DQ5.

Case presentation

Our patient, a Caucasian man, was 34 years of age when he received his first deceased donor renal transplant. After 8 years, his first transplant failed from chronic allograft dysfunction and an earlier bout of Banff 1A cellular rejection. The second deceased donor kidney transplant was initially allocated to the patient due to a 0 out of 6 mismatch. The B cell crossmatch was mildly positive, while the T Cell crossmatch was negative. Subsequent assays showed that the patient had preformed antibodies for human leukocyte antigen DQ5 against his second donor. Despite having preformed antibodies against the donor, the patient continues to have excellent allograft function two years after his second renal transplant.

Conclusion

The presence of pre-existing antibodies against human leukocyte antigen DQ5 does not preclude transplantation. The relevance of having other antibodies against class II human leukocyte antigens prior to transplantation remains to be studied.

Successful treatment of class V+IV lupus nephritis with multitarget therapy

Treatment of class V+IV lupus nephritis remains unsatisfactory despite the progress made in the treatment of diffuse proliferative lupus nephritis. In this prospective study, 40 patients with class V+IV lupus nephritis were randomly assigned to induction therapy with mycophenolate mofetil, tacrolimus, and steroids (multitarget therapy) or intravenous cyclophosphamide (IVCY). Patients were treated for 6 mo unless complete remission was not achieved, in which case treatment was extended to 9 mo. An intention-to-treat analysis revealed a higher rate of complete remission with multitarget therapy at both 6 and 9 mo (50 and 65%, respectively) than with IVCY (5 and 15%, respectively). At 6 mo, eight (40%) patients in each group experienced partial remission, and at 9 mo, six (30%) patients receiving multitarget therapy and eight (40%) patients receiving IVCY experienced partial remission. There were no deaths during this study. Most adverse events were less frequent in the multitarget therapy group. Calcineurin inhibitor nephrotoxicity was not observed, but three patients developed new-onset hypertension with multitarget therapy. In conclusion, multitarget therapy is superior to IVCY for inducing complete remission of class V+IV lupus nephritis and is well tolerated.

Circulating anti-endothelial cell antibodies are associated with poor outcome in renal allograft recipients with acute rejection

BACKGROUND AND OBJECTIVES

Anti-endothelial cell antibody (AECA) can cause hyperacute rejection and immediate graft loss after renal transplantation; however, its prevalence and significance during acute rejection are unknown. Previous studies suggested that AECA may be detected in recipients with acute vascular rejection (AVR).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We retrospectively analyzed 653 cadaveric renal transplant recipients; circulating AECA was positive in 13 of 47 cases of AVR; another two cases of hyperacute rejection also had detectable AECA. Twenty-six cases of AVR without circulating AECA were selected as controls.

RESULTS

AECA-positive AVR usually occurred within 1 yr after transplantation and mostly was resistant to steroid treatment. Compared with the control group, the AECA-positive group was associated with a significantly lower 1-yr graft survival rate (46.7 versus 80.5%; P = 0.038), and more patients had histologic interstitial plasma cell infiltration (53.8 versus 11.5%; P = 0.005). More patients with AECA-positive AVR experienced another one or more episodes of acute rejection during 1 yr of follow-up (75.0 versus 13.0%; P = 0.003). AECA-positive AVR with C4d deposition in peri-tubular capillaries had the worst outcome in this cohort, and it accounted for 38.5% graft loss in AVR. AECA in turn accounted for 71.4% of graft loss in C4d(+) AVR.

CONCLUSIONS

Circulating AECA is associated with poor outcome in renal allograft recipients with acute rejection and should be monitored regularly.

Effects of cyclosporine, tacrolimus and sirolimus on vascular changes related to immune response

BACKGROUND

Despite the use of newer immunosuppressors such as sirolimus (SRL) and tacrolimus (TRL) in heart transplantation, the rate of humoral rejection has remained unchanged. The aim of this study was to analyze the immunologic and histologic effects of cyclosporine (CsA), SRL, and TRL in a porcine model of arterial transplantation.

METHODS

Each transplant recipient animal (n = 49) received an autograft and an allograft and was then allocated to one of four treatment groups and a 7- or 30-day follow-up period, as follows: a WOT group (without immunosuppressor treatment), 7 days (n = 6) and 30 days (n = 5); a CsA group, 7 days (n = 5) and 30 days (n = 6); an SRL group, 7 days (n = 7) and 30 days (n = 8); and a TRL group, 7 days (n = 6) and 30 days (n = 6). The presence of donor-specific antibodies (DSA) was tested at the end of the follow-up period. Morphometric parameters and inflammatory infiltration were analyzed in the explanted grafts.

RESULTS

At 30-day follow-up, SRL was the only treatment capable of suppressing DSA formation (0 of 7 vs 4 of 5 in the WOT group; p < 0.05). SRL completely prevented aneurismal dilation and reduced the number of macrophages in the allografts. TRL treatment achieved a greater reduction of T lymphocytes. CsA did not prevent the reduction in total vascular area at 7 days that was achieved with the SRL and TRL groups. Animals treated with CsA had the largest number of T lymphocytes and macrophages in both follow-up periods.

CONCLUSIONS

SRL prevented DSA formation and reduced the number of macrophages as compared with TRL and CsA.

Peritubular capillary C4d deposition in lupus nephritis different from antibody-mediated renal rejection

C4d deposition in peritubular capillaries (PTC) has been used as a marker of antibody-mediated rejection (AMR). However, PTC C4d deposition is not described in patients with lupus nephritis (LN). C4d deposition in PTC was detected in 455 patients with biopsy proven LN in the present study. Renal tissues from 21 cases of acute AMR served as controls. C4d deposition in PTC was found in 31 patients (6.81%) with LN. Patients with PTC C4d positive showed higher SLEDAI score and higher frequency of hypocomplementemia as compared to C4d negative. The prevalence of ANA, anti-dsDNA, anti-Sm and ACA were higher in C4d positive group, and most of these patients showed the diffuse proliferative glomerular lesion. In contrast with acute AMR, the staining pattern of C4d was granular deposition and the detection of C4d along PTC was accompanied by deposition of IgG and C1q or C3. Electron dense deposition on PTC was observed in most of LN patients. In conclusion, C4d deposition in PTC could be found in a small part of patients with LN. Our study suggested for the first time that C4d positive deposition were close relation with the higher disease activity of LN, and that immune complex formation might be involved in PTC C4d deposition in LN patients, Such PTC C4d deposition is distinct from that of AMR.

Acute antibody-mediated rejection of renal transplant: pathogenetic and diagnostic considerations

CONTEXT

Acute antibody-mediated rejection (AMR) has emerged recently as an important cause of graft failure.

OBJECTIVE

To review the pathogenetic, clinicopathologic, and diagnostic considerations of AMR.

DATA SOURCES

Review of literature and the authors' experience.

CONCLUSIONS

Acute antibody-mediated rejection is mediated by antibodies specific for donor antigens, which bind to target antigens and activate the complement system, culminating in tissue injury. The clinical manifestation of AMR is not specific, and transplant biopsy is needed for diagnosis. The glomeruli show thrombosis or neutrophils or mononuclear leukocytes in capillary lumens. The tubulointerstitial compartment shows edema, hemorrhage, necrosis, mild inflammation, and neutrophils or mononuclear leukocytes in the peritubular capillary lumens. The blood vessels show thrombosis, thrombotic microangiopathy, fibrinoid necrosis, or transmural vasculitis. Strong staining for C4d in the peritubular capillaries is characteristic. A definitive diagnosis of AMR requires (1) morphologic evidence of acute tissue injury, (2) immunopathologic evidence for antibody action, and (3) serologic evidence of circulating donor-specific antibodies. Acute antibody-mediated rejection should be suspected if some but not all 3 criteria are met. Since effective treatment is currently available, accurate and timely diagnosis of AMR is essential.

The classification and treatment of antibody-mediated renal allograft injury: Where do we stand?

Since the acceptance of the detection of C4d in allografts as a reliable tool to mark a humoral alloresponse, de novo antibody-induced graft injury has attracted much attention. Antibodies and B cells are the new frontier in transplantation. At this juncture carefully designed studies are critical in order to gain solid diagnostic, therapeutic, and prognostic knowledge about the role of antibodies in graft injury and to avoid any confusion and misconception. One prerequisite is the strict adherence to refined classification systems of renal transplant rejection that carefully split and categorize different phenotypes of humoral mediated graft damage and ideally also include information on anti-donor antibody specificity and titers. Sun and colleagues follow this concept and provide evidence that mixed cellular and antibody-mediated graft rejection can respond favorably to intensified immunosuppression with tacrolimus and mycophenolate mofetil. What will the future bring to treat rejection episodes with a dominant, co-dominant, or minor antibody response?