Antibodies In Renal Transplantation Research Articles

Clinical conundrums in pediatric kidney transplantation: What we know about the role of angiotensin II type I receptor antibodies in pediatric kidney transplantation and the path forward.

Antibodies to angiotensin II type 1 receptor (AT1R-Abs) are among the most well-studied non-HLA antibodies in renal transplantation. These antibodies have been shown to be common in pediatric kidney transplantation and associated with antibody-mediated rejection (AMR), vascular inflammation, development of human leukocyte donor-specific antibodies (HLA DSA), and allograft loss. As AT1R-Ab testing becomes more readily accessible, evidence to guide clinical practice for testing and treating AT1R-Ab positivity in pediatric kidney transplant recipients remains limited. This review discusses the clinical complexities of evaluating AT1R-Abs given the current available evidence.

WCN24-2721 Donor-Specific Antibodies in Renal Transplantation and Their Impact on Kidney Graft Survival

WCN24-2721 Donor-Specific Antibodies in Renal Transplantation and Their Impact on Kidney Graft Survival

HLA Eplet Mismatch Analysis of a Large Multi-Center Pediatric Heart Transplant Cohort: Not All Transplants are Immunologically Equal

<h3>Purpose</h3> Allograft rejection is driven by HLA disparity between donor and recipient despite of the use of various immunosuppression protocols. To better define the risk of allograft failure or complications from overt immunosuppression we applied the epitope-based mismatch approach to quantify the degree of HLA disparity in a in a large multi-center pediatric heart transplant (pHTX) cohort that has been followed for 3-5 years. <h3>Methods</h3> 274 pHTX recipient/donor pairs were retrospectively HLA genotyped by Next-Generation Sequencing and evaluated for HLA allele (alMM) and eplet mismatch (epMM) loads. HLAMatchmaker version 2.2 was used to determine epMM load at HLA-A/B/C, -DRB1/3/4/5, -DQA1/DQB1 and -DPA1/DPB1. <h3>Results</h3> Overall, the average total alMM was 13(±2). 76% were ≥5 HLA-A/B/C allele mismatches, 67% were ≥3 HLA-DRB and ≥3 HLA-DQ allele mismatch. The average epMM load was 60 (±17), range 16-112 (Table). 94% of cases had >11 HLA-DR or DQ epMM, a threshold previously shown to be associated with development of HLA donor-specific antibody in renal transplantation. While 159 cases (61.6%) had both DR and DQ epMM >11, only DR epMM or only DQ epMM >11 occurred in 31 (12.0%) and 50 (19.4%) cases, respectively (Figure). Therefore, this cohort can be divided into 3 groups for Class II epMM load: 6% (16) of cases with low, 36% (99) with intermediate and 58% (159) with high load. <h3>Conclusion</h3> Although this pHTx cohort is highly mismatched, for HLA alleles, there is a large range based on epMM, especially for HLA-DR and -DQ indicating that allele level typing is insufficient for determination of the true degree of mismatching. By correlating these data with clinical parameters, we aim to determine risk stratification based on epMM load in pediatric heart transplantation.

Testing for donor-specific antibodies in renal transplantation: Indian perspective

The evaluation of donor-specific antibodies by Luminex single-antigen bead assay (in addition to other crossmatch tests) to assess pretransplant immunological risk should be performed in recipients (especially with a history of prior sensitization) even in resource-constrained settings as this approach can help in better risk stratification, to decide on transplant eligibility, selection of immunologically favorable donor, to plan desensitization protocol and induction therapy that can lead to the reduction of posttransplant rejection rates and better graft survival. Despite the cost, it is justified to use these sensitive assays in selected cases even in a cost-limited setting as this enables earlier and better-matched transplant, and avoidance of morbidity and poor graft survival.

Non-HLA Antibodies in Renal Transplantation, Where Do We Stand?

Non-HLA Antibodies in Renal Transplantation, Where Do We Stand?

P003 Successful kidney transplantation across positive crossmatches with strong donor-specific HLA-DP antibodies

The role of anti-HLA-DP antibodies in renal transplantation is poorly defined. One of our kidney re-list candidates with 99% CPRA (+ many strong DP antibodies) received a kidney offer from a single DP1 mismatched deceased donor. The patient displayed strong DP1 antibodies (MFI = 10930) and thereby positive B cell pronase crossmatch (MCS = 125; cutoff is 120 MCS). Since the donor is highly matched and crossmatch was borderline positive, we move forward with this transplantation with anti-CD25 mAb induction and a single dose IVIG (2 g/kg) at day 1 post-tx. The graft was functioning and no rejection noticed in 6 month biopsy. The aim of the present study was to expand similar transplants for highly sensitized patients across DP donor-specific antibodies (DSA) with positive or negative B cell XM. 16 candidates (4 female listed for 1st tx, 6 females and 6 males listed for re-tx) with cPRA ranging from 75 to 100% (9 candidates had cPRA 100%) were transplanted with DP DSAs of greater than 5000 MFI (9 had MFI > 100,00). Retrospective FXM were done on 15 patients. Kidney biopsy data on 12 patients were evaluated for C4d deposition and AMR. One Lambda single antigen bead (SAB) assay was used to test HLA antibodies. 9 of 15 retrospective B FXM were positive, and the positive B FXM had DP DSAs of >10000 MFI (pronase MCS are generally ∼200). The levels of DP DSAs were plotted at pre- and post-tx (1 week, 1 month and 6 months) sera, which show significant decreases in DP DSAs in all 16 recipients (see figure). The 6 month protocol biopsy found no AMR in 9 recipients (8 were C4d- and 1 was C4d+), and C4d- AMR+ in 3 patients. One recipient developed de novo DSA to A32 (MFI = 14,000) but was undetectable at 6 months post-tx. The presence of HLA-DP antibodies particularly in broadly sensitized re-list candidates decrease the chance of finding a compatible donor. Results from this study show that patients can be transplanted across the HLA-DP DSAs without affecting graft survival, and therefore increasing access for broadly sensitized candidates.Download : Download high-res image (222KB)Download : Download full-size image

Significance of De novo Donor-Specific Anti-HLA Antibodies in Renal Transplantation: A Single Center Experience

T cell-mediated rejection (TCMR) became controllable, and the long-term renal graft survival came to be obtained by the recent progress and innovation of the immuno-suppressants. Whereas the prophylaxis and control of antibody-mediated rejection (ABMR) caused by donor-specific anti-HLA antibody (DSA) are still insufficient and affect the long-term renal graft survival. DSA was classified roughly as follows: preexisting DSA existed in the patients before renal transplantation (RTx), and de novo DSA produced in the patients after RTx. There are many reports about the effect that preexisting DSA gives to a renal graft, and the treatment for ABMR with preexisting DSA is established to some degree. In contrast to preexisting DSA, it cannot be said that de novo DSA are considered enough at present. In this study, we examined the impact that de novo DSA gave to a renal graft in 40 RTx patients under treatment in our hospital. Although there was no significant difference as to the renal graft function in DSA positive and negative group, the renal graft survival showed the tendency that was better in a DSA negative group than a positive group (85% vs. 55%, P=0.0553). We perform monitoring of the de novo DSA positively and should contribute to the prognosis improvement of the renal graft in future.

Evidence for an important role of both complement-binding and noncomplement-binding donor-specific antibodies in renal transplantation.

The review describes the current clinical relevance of circulating anti-human leukocyte antigen (anti-HLA) antibodies in kidney transplantation and discusses recent improvements in their characterization that provide new insights into the identification and management of important clinical outcomes. Recent studies addressing the relationships between donor-specific anti-HLA antibody (HLA-DSA) properties (i.e., their strength, complement-binding capacity, and IgG subclass composition) and allograft injury and survival have highlighted their relevance in the prediction of antibody-mediated injury and allograft loss. Antibody-mediated rejection is the leading cause of kidney allograft loss. Although considerable experimental and clinical evidence suggests a causal effect of circulating HLA-DSAs in antibody-mediated rejection and allograft failure, HLA-DSAs induce a wide spectrum of injuries to the allograft that illustrate the need to delineate the characteristics of HLA-DSAs that confer pathogenesis. Current risk stratification is based on HLA-DSA characteristics, including antibody specificity, HLA class, and strength. Recently, the complement-binding capacity of HLA-DSAs has been recognized as a clinically relevant marker for predicting pathogenicity and allograft loss. Emerging data also support a role for HLA-DSA IgG subclass composition in discriminating distinct patterns of antibody-mediated injury. This progress in our understanding of HLA-DSA pathogenicity provides new tools to stratify individual immunological risks. However, specific prospective studies addressing immunological risk stratification in large and unselected populations are required to define the clinical benefit and cost-effectiveness of such a comprehensive assessment of HLA-DSAs before implementation in current clinical practice.

Incidence and impact of anti-HLA-DP antibodies in renal transplantation.

The role of anti-HLA-DP antibodies in renal transplantation is poorly defined. This study describes the impact of donor (donor-specific antibody [DSA]) and non-donor-specific antibodies against HLA-DP antigens in renal transplant patients. Of 195 consecutive patients transplanted between September 2009 and December 2011, 166 primary kidney recipients and their donors were typed (high-resolution) for DP antigens. Sera taken pre-transplant and at 1, 3, 6, 9, and 12months, and annually post-transplant were retrospectively tested for anti-DP antibodies using single-antigen beads. In 81 (49%) patients, anti-DP antibodies were found; 64% (n=52) of patients were positive in the pre-transplant samples and 36% (n=29) were positive exclusively post-transplant. The median time from transplantation to antibody was 20.9months. Fifty-five percent (n=16) of the de novo anti-DP antibodies were accompanied by another de novo DSA. Anti-DP antibody-positive patients had a higher rate of rejection (compared with anti-DP antibody-negative patients, P=.01). The estimated glomerular filtration rate declined more with anti-DP antibodies (-5.5% vs +26%). Antibodies against HLA-DP antigens are common. De novo anti-DP antibodies commonly appear after acute rejection and accompany DSA, which makes it difficult to determine whether anti-DP antibodies are the cause or the consequence of graft injury.

Donor-specific anti-HLA antibodies in renal transplantation

Donor-specific anti-HLA antibodies in renal transplantation

Anti–Angiotensin Type 1 Receptor Antibodies Associated With Antibody-Mediated Rejection in Patients Without Preformed HLA-Donor–Specific Antibody

IntroductionAngiotensin II is a peptide hormone involved in the renin-angiotensin system (RAS). Anti–angiotensin receptor 1 (AT1R) antibodies are implicated in stimulating RAS and are suspected to have some adverse impacts on renal transplantation outcome. MethodsFrom November 2009 to February 2012, 37 remaining sera from renal transplantation recipients with biopsy-proven antibody-mediated rejection (AMR) (n = 6), acute cellular rejection (ACR) (n = 23), and AMR + ACR (n = 8) without preformed human leukocyte antigeon (HLA) antibodies were tested with anti-AT1R antibody assay. Forty-two control patients without rejection also were analyzed. ResultsThe frequency of elevated anti-AT1R antibodies was higher in patients with AMR (n = 14) compared to controls (28.6% vs 4.9%, P = .03, OR = 8.0). It was also higher in patients with AMR + ACR (n=8) (37.5% vs 4.9%, P = .03, OR = 12.0). There was no difference in frequencies of elevated anti-AT1R antibody in patients with ACR. ConclusionAnti-AT1R antibodies were suspected to be associated with occurrence of AMR without preformed HLA antibodies in renal transplantation. Further studies in a larger number of patients are needed.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Role of anti-vimentin antibodies in renal transplantation.

The role of non-HLA antibodies in rejection is not clear. We investigate whether antibodies to vimentin are made after renal transplantation and if production is associated with interstitial fibrosis and tubular atrophy (IFTA). In this retrospective study, sera from 70 recipients of renal allografts (40 controls, 30 IFTA) were studied. The biopsy diagnosis of interstitial fibrosis and tubular atrophy (IFTA) was based on random, cause-indicating biopsies. Sera were collected pretransplant and at 3 monthly intervals up to 5 years posttransplant or diagnosis of IFTA and assayed by ELISA for IgM and IgG anti-vimentin antibodies (AVA) and HLA antibodies. Mean titers of IgM AVA were higher at every year after transplantation compared with pretransplant for both IFTA and controls groups (P<0.001). There was no difference in the mean level of IgM AVA achieved by IFTA and control groups. The mean pretransplant levels of IgG AVA in the IFTA and control group were 18.2±11.7 and 11.0±8.1, respectively (P=0.001). There was a significant increase between the pretransplant mean levels of IgG AVA and the levels at years 1 to 4 in the IFTA group (years 1-3, P<0.0001, year 4 P=0.003) but not in the controls. There was no significant difference between the numbers of IFTA or control patients achieving a positive value (mean+2SD of pretransplant antibody titers) of IgM AVA (50% versus 37.5%, respectively) or IgG AVA (26.6% versus 12.5%, respectively). There was no association between production of HLA and AVA antibodies. Posttransplant production of IgM AVA is not associated with IFTA. The production of IgG AVA by a minority of IFTA patients suggests that in some individuals, IgG AVA may be involved in the pathology of IFTA.

Significance of HLA IgM and IgM Donor Specific Antibodies in Renal Transplantation.

Significance of HLA IgM and IgM Donor Specific Antibodies in Renal Transplantation.

Excellent Results of Immunocomplex Capture Fluorescence Analysis-I for Cross-Match Test in Renal Transplantation

A flow cytometry cross-match (FCXM) test is the gold standard for detection of human leukocyte antigen (HLA) antibodies in renal transplantation because of its high sensitivity. However, this technique can produce false-positive results when non-HLA antibodies or low-titer donor-specific antibodies (DSA) are detected. To determine the clinical relevance of the recently introduced novel cross-match test termed immunocomplex capture fluorescence analysis (ICFA), we retrospectively compared the results of ICFA and FCXM, including a single-antigen bead test for detection of DSA in renal transplant recipients. We found a correlation of 71.4% (235/329) between the results of ICFA-I and FCXM-T, whereas that between ICFA-II and FCXM-B was 41.1% (134/326). Ninety-four patients were ICFA-I negative and FCXM-T positive, and 188 were ICFA-II negative and FCXM-B positive, whereas 46.8% (44/94) and 61.7% (116/188) were found to be DSA-I and DSA-II negative, respectively, which classified them into the non-HLA antibody and low-titer DSA groups, respectively. The mean value of molecules of equivalent soluble fluorochrome for DSA-I was 22,994 in the ICFA-I–positive group, which was significantly higher than 2117 in the negative group (P < .0001), whereas there was no significant difference for DSA-II between the ICFA-II–positive and ICFA-II–negative groups. Graft survival in the ICFA-I–negative group was significantly higher than that in the ICFA-I–positive group (P = .0058). Our results indicate that ICFA-I does not respond to non-HLA antibodies or low-titer DSA, which have influence on graft survival. Therefore, this novel hybrid test, which combines cross-match testing and HLA antibody detection functions, may be useful for clinical pretransplantation evaluation of renal transplantation patients.

The Presence of Donor-Specific Antibodies in Renal Transplantation

Determining the presence of anti-HLA antibodies before transplantation is an important factor to prevent loss of function among renal transplantations. In addition, recent studies have shown that not only the pretransplantation existence of anti-HLA antibody but also posttransplantation donor-specific antibodies (DSA) and non–donor-specific antibodies are significantly associated with allograft rejection or loss of graft function. This study presented DSA among patients after renal transplantation together with graft function and survival.

Anti-Leb (Lewis) antibody in renal transplantation, emphasizing the role of transfusion medicine in organ transplantation

Anti-Leb (Lewis) antibody in renal transplantation, emphasizing the role of transfusion medicine in organ transplantation

The mechanisms of acute transplant rejection revisited

For many years, acute rejection has been considered as a typical response of the adaptive immunity system. However, recent investigations have revealed a critical role for innate immunity as a pivotal trigger in adaptive immune responses. Danger signals released by cells damaged or killed by injury or disease may be intercepted by Toll-like receptors (TLRs) that alarm the dendritic cells (DCs) through the activation of transcription factors. In the presence of an inflammatory milieu created by other components of the innate immunity, DCs become mature and present the antigen to naïve T cells. The activation of T cells requires both a signal engendered by the presentation of the antigen to the T cell receptor and costimulatory signals generated by the contact between molecules displayed by antigen-presenting cells (APCs) and by T cells. Once activated, T cells encode and synthesize interleukin 2 (IL-2) and other cytokines that provide the signals for cell differentiation and proliferation. Until recently, little attention was paid to the role of antibodies in renal transplantation. However, there is mounting evidence that a number of kidney allografts fail as a consequence of a rejection caused by antibodies specifically directed against major histocompatibility complex antigens, class I or II, of the recipient. A critical role in antibody-mediated rejection (AMR) is played by complement. A number of therapeutic attempts have been tried to prevent or treat AMR. The still open question is whether the antibodies we detect are those responsible for tissue damage or not.

Use of Monoclonal Antibodies in Renal Transplantation

Monoclonal antibodies are applied in various settings in renal transplantation. Depleting T-cell antibodies are used for treatment of steroid-resistant acute rejection and as induction therapy to reduce the intensity of concomitant immunosuppressive drug therapy. Induction therapy with the nondepleting IL-2 receptor antagonists basiliximab and daclizumab, added to cyclosporine-based regimens, reduces the incidence of acute rejection without side effects. However, an increase in long-term graft and patient survival has not been demonstrated yet. The B-cell-targeting antibody rituximab is used in blood group ABO-incompatible transplantation, in desensitization protocols, and for treatment of antibody-mediated rejection. Eculizumab interrupts the complement pathway and is a promising tool for the treatment of antibody-mediated rejection and post-transplant hemolytic-uremic syndrome. Future options are monoclonal antibodies with new molecular targets and antibodies that can be used for maintenance immunosuppression in order to avoid the toxicity of existing drugs. However, in several cases, the development of new monoclonal antibodies has been hampered by safety issues.

49-P: Clinical Relevance of Pretransplant Donor-Specific HLA Antibodies in Renal Transplantation

49-P: Clinical Relevance of Pretransplant Donor-Specific HLA Antibodies in Renal Transplantation