Effects Of Donor-specific Antibodies Research Articles

Pre-transplant donor specific antibodies in ABO incompatible kidney transplantation - data from the Swiss transplant cohort study.

Living donor (LD) kidney transplantation in the setting of ABO blood group incompatibility (ABOi) has been previously reported to be associated with increased risk for antibody-mediated rejection (ABMR). It is however unclear if the presence of pre-transplant donor specific antibodies (DSA) works as an additive risk factor in the setting of ABOi and if DSA positive ABOi transplants have a significantly worse long-term outcome as compared with ABO compatible (ABOc) DSA positive transplants. We investigated the effect of pre-transplant DSA in the ABOi and ABOc setting on the risk of antibody-mediated rejection (ABMR) and graft loss in a cohort of 952 LD kidney transplants. We found a higher incidence of ABMR in ABOi transplants as compared to ABOc transplants but this did not significantly affect graft survival or overall survival which was similar in both groups. The presence of pre-transplant DSA was associated with a significantly increased risk of ABMR and graft loss both in the ABOi and ABOc setting. We could not detect an additional risk of DSA in the ABOi setting and outcomes were comparable between DSA positive ABOi and ABOc recipients. Furthermore, a combination of DSA directed at both Class I and Class II, as well as DSA with a high mean fluorescence intensity (MFI) showed the strongest relation to ABMR development and graft loss. The presence of pre-transplant DSA was associated with a significantly worse long-term outcome in both ABOi and ABOc LD kidney transplants and our results suggests that the risk associated with pre-transplant DSA is perhaps not augmented in the ABOi setting. Our study is the first to investigate the long-term effects of DSA in the ABOi setting and argues that pre-transplant DSA risk could potentially be evaluated similarly regardless of ABO compatibility status.

Effects of donor-specific antibodies on engraftment and long-term survival after allogeneic hematopoietic stem cell transplantation-A systematic review and meta-analysis.

The presence of donor-specific antibodies (DSAs) have been reported to be associated with an increased risk of primary graft failure following allogeneic hematopoietic stem cell transplantation (allo-HSCT), but its effects on the time to engraftment and long-term outcomes remain unclear. We performed a systematic review and meta-analysis of studies investigating the impact of DSAs on engraftment and long-term survival of patients undergoing allo-HSCT. We systematically searched PubMed, Embase, the Cochrane Library, and CBM. Data were analyzed using RevMan5.4. Pooled hazard ratio (HR), standard mean difference (SMD) or odds ratio (OR) and corresponding 95% confidence interval (CI) are calculated for time-to-event data, continuous data, discontinuous data respectively. 17 eligible studies were included, involving 2169 patients main receiving haploidentical SCT (haplo-SCT) or umbilical cord blood transplantation (UCBT). Meta-analysis showed that DSAs-positive patients are associated with significantly higher risk of GF(OR = 12.87, 95%CI, 6.45-25.70; P < 0.00001; OR = 4.76, 95%CI, 2.88-7.87), poorer neutrophil engraftment (HR = 2.20, 95%CI, 1.02-4.73; P = 0.04; HR = 1.83, 95%CI, 1.46-2.30; P < 0.00001), worse OS (HR = 3.19, 95%CI, 1.85-5.50; P < 0.0001; HR = 1.68, 95%CI, 1.04-2.71; P = 0.03), and inferior PFS (HR = 4.25, 95%CI, 1.59-11.40; P = 0.004; HR = 4.83, 95%CI, 1.65-14.12; P = 0.004) in haplo-SCT and UCBT, respectively.

Unraveling complexity of antibody-mediated rejections, the mandatory way towards an accurate diagnosis and a personalized treatment

Antibody-mediated rejection (ABMR) remains one of the most challenging issues after organ transplantation and particularly after kidney transplantation. Despite many progresses during the last decade, ABMR is still the main cause of kidney graft loss and this all over the post- transplant period.In this review, we describe the recent knowledge about molecular and cellular mechanisms involved in ABMR. We focused our report on the role of the complement pathway in the process of ABMR and we give some insights into the role of inflammatory cells, NK lymphocytes and the role of endothelial cells. We further describe the potential role of non-HLA antibodies, of which the importance has been increasingly emphasized in recent years.Overall, this report could be of interest for all physicians who are working in the field of organ transplantation or who are working in the field of immunology. It gives essential information to understand new diagnosis advances and further therapeutic approaches.Antibody-mediated rejection (ABMR) is the leading cause of graft failure ([1,2]). In contrast to T-cell mediated rejection usually sensitive to steroids, active ABMR remains a therapeutic challenge. ABMR diagnosis relies on the presence of renal injuries and donor-specific antibodies (DSA) (HLA and non HLA antibodies) with sometimes the evidence of interaction between DSA and graft endothelium. Regularly revised during expert conferences, ABMR definition is currently categorized as active or chronic active. [3] The emergence of validated molecular assays targeting a better phenotyping of ABMR and the recent advances regarding the detrimental effect of DSA directed against minor antigens open the way to a better assessment of the heterogeneity of ABMR. In this review, we will address new aspects of ABMR regarding its mechanisms, diagnosis and treatments.

The impact of pre-transplant donor specific antibodies on the outcome of kidney transplantation – Data from the Swiss transplant cohort study

BackgroundPre-transplant donor specific antibodies (DSA), directed at non-self human leukocyte antigen (HLA) protein variants present in the donor organ, have been associated with worse outcomes in kidney transplantation. The impact of the mean fluorescence intensity (MFI) and the target HLA antigen of the detected DSA has, however, not been conclusively studied in a large cohort with a complete virtual cross-match (vXM).MethodsWe investigated the effect of pre-transplant DSA on the risk of antibody-mediated rejection (ABMR), graft loss, and the rate of eGFR decline in 411 DSA positive transplants and 1804 DSA negative controls.ResultsPre-transplant DSA were associated with a significantly increased risk of ABMR, graft loss, and accelerated eGFR decline. DSA directed at Class I and Class II HLA antigens were strongly associated with increased risk of ABMR, but only DSA directed at Class II associated with graft loss. DSA MFI markedly affected outcome, and Class II DSA were associated with ABMR already at 500-1000 MFI, whereas Class I DSA did not affect outcome at similar low MFI values. Furthermore, isolated DSA against HLA-DP carried comparable risks for ABMR, accelerated eGFR decline, and graft loss as DSA against HLA-DR.ConclusionOur results have important implications for the construction and optimization of vXM algorithms used within organ allocation systems. Our data suggest that both the HLA antigen target of the detected DSA as well as the cumulative MFI should be considered and that different MFI cut-offs could be considered for Class I and Class II directed DSA.

The MHC class I MICA gene is a histocompatibility antigen in kidney transplantation

The identity of histocompatibility loci, besides human leukocyte antigen (HLA), remains elusive. The major histocompatibility complex (MHC) class I MICA gene is a candidate histocompatibility locus. Here, we investigate its role in a French multicenter cohort of 1,356 kidney transplants. MICA mismatches were associated with decreased graft survival (hazard ratio (HR), 2.12; 95% confidence interval (CI): 1.45–3.11; P < 0.001). Both before and after transplantation anti-MICA donor-specific antibodies (DSA) were strongly associated with increased antibody-mediated rejection (ABMR) (HR, 3.79; 95% CI: 1.94–7.39; P < 0.001; HR, 9.92; 95% CI: 7.43–13.20; P < 0.001, respectively). This effect was synergetic with that of anti-HLA DSA before and after transplantation (HR, 25.68; 95% CI: 3.31–199.41; P = 0.002; HR, 82.67; 95% CI: 33.67–202.97; P < 0.001, respectively). De novo-developed anti-MICA DSA were the most harmful because they were also associated with reduced graft survival (HR, 1.29; 95% CI: 1.05–1.58; P = 0.014). Finally, the damaging effect of anti-MICA DSA on graft survival was confirmed in an independent cohort of 168 patients with ABMR (HR, 1.71; 95% CI: 1.02–2.86; P = 0.041). In conclusion, assessment of MICA matching and immunization for the identification of patients at high risk for transplant rejection and loss is warranted.

Complement-Based Therapy in the Management of Antibody-Mediated Rejection.

Antibody-mediated rejection (AMR) is one of the leading causes of kidney allograft failure and is usually mediated by anti-human leukocyte antigen donor-specific antibodies (DSAs). Activation of classical pathway of the complement system is responsible for downstream effects of DSA and account for significant manifestations of AMR. Currently, the treatment of AMR is based on strategies to remove preformed antibodies or to prevent their production; however, these strategies are often unsuccessful. It is theoretically possible to inhibit complement activity to prevent the effect of DSA on kidney allograft function. Complement inhibitors such as eculizumab, a complement 5 monoclonal antibody, and complement 1 esterase inhibitors (C1 INHs) have been used in prevention and treatment of AMR with variable success. Eculizumab and C1 INH seem to reduce the incidence of early AMR and allow transplantation in highly sensitized kidney transplant recipients, but data on their long-term effect on kidney allograft function are limited. Several case reports described the successful use of eculizumab in the treatment of AMR, but there are no randomized controlled studies that showed efficacy. Treatment of AMR with C1 INH, in addition to standard of care, did not change short-term outcome but long-term studies are underway.

Developing DSA Post-Lung Transplant - Identifying Risk Factors

Purpose Donor specific antibodies (DSA) to mismatched human leukocyte antigens have been reported to adversely affect the outcomes of lung transplantation. This study aimed to identify the risk factors for the development of DSA within 1-year post-transplant and examine its impact on recipients’ medium-term survival. Methods Recipients’ age, type of transplantation (single lung or bilateral lungs), pre-existing antibodies, post-op DSA, method of transplantation (ECMO, off-pump or on-pump), primary graft failure (PGD) grade 3 at 72hrs, blood transfusion, post-op ITU stay, ECMO usage and renal support, and survival status were collected from the unit's database. Binary logistic regression was used to identify risk factors for the development of post-op DSA within 1-year post-transplant. Multivariable Cox regression was performed to identify risk factors for survival. Results From January 2012 to October 2017, 259 adult patients received lung transplantation in our unit and 242 (93.4%) survived beyond 30-day post-op. Recipients who died within 30-day post-transplant were not included, as the causes of their death were less likely to be influenced by or associated with post-op DSA. Among these 242 recipients, 46 (19.0%) had pre-existing antibodies and 129 (53.3%) had DSA detected within 1-year post-transplant. Among all the potential risk factors, transplantation performed with ECMO (p = 0.007, OR 3.06, 95% CI: 1.36-6.90) are significantly associated with post-op DSA within 1-year post-transplant. Age (p = 0.009, OR 1.03, 95% CI: 1.01-1.05), post-op renal support (p = 0.015, OR 2.23, 95% CI: 1.17-4.26), PGD grade 3 at 72hrs (p = 0.001, OR 2.79, 95% CI: 1.54-5.05), and red blood cell transfusion (p < 0.001, OR 1.17, 95% CI: 1.11-1.23) are associated with worse medium-term survival, but neither pre-existing antibodies (p = 0.454) or post-op DSA (p = 0.479) has an impact on survival. Conclusion Use of ECMO for lung transplantation is associated with DSA development within 1-year post-transplantation. However, the presence of DSA within 1-year post-transplant has no impact on medium-term survival in this cohort. Further study is required to look at the effect of DSA on the development of chronic lung allograft dysfunction and long-term survival. Donor specific antibodies (DSA) to mismatched human leukocyte antigens have been reported to adversely affect the outcomes of lung transplantation. This study aimed to identify the risk factors for the development of DSA within 1-year post-transplant and examine its impact on recipients’ medium-term survival. Recipients’ age, type of transplantation (single lung or bilateral lungs), pre-existing antibodies, post-op DSA, method of transplantation (ECMO, off-pump or on-pump), primary graft failure (PGD) grade 3 at 72hrs, blood transfusion, post-op ITU stay, ECMO usage and renal support, and survival status were collected from the unit's database. Binary logistic regression was used to identify risk factors for the development of post-op DSA within 1-year post-transplant. Multivariable Cox regression was performed to identify risk factors for survival. From January 2012 to October 2017, 259 adult patients received lung transplantation in our unit and 242 (93.4%) survived beyond 30-day post-op. Recipients who died within 30-day post-transplant were not included, as the causes of their death were less likely to be influenced by or associated with post-op DSA. Among these 242 recipients, 46 (19.0%) had pre-existing antibodies and 129 (53.3%) had DSA detected within 1-year post-transplant. Among all the potential risk factors, transplantation performed with ECMO (p = 0.007, OR 3.06, 95% CI: 1.36-6.90) are significantly associated with post-op DSA within 1-year post-transplant. Age (p = 0.009, OR 1.03, 95% CI: 1.01-1.05), post-op renal support (p = 0.015, OR 2.23, 95% CI: 1.17-4.26), PGD grade 3 at 72hrs (p = 0.001, OR 2.79, 95% CI: 1.54-5.05), and red blood cell transfusion (p < 0.001, OR 1.17, 95% CI: 1.11-1.23) are associated with worse medium-term survival, but neither pre-existing antibodies (p = 0.454) or post-op DSA (p = 0.479) has an impact on survival. Use of ECMO for lung transplantation is associated with DSA development within 1-year post-transplantation. However, the presence of DSA within 1-year post-transplant has no impact on medium-term survival in this cohort. Further study is required to look at the effect of DSA on the development of chronic lung allograft dysfunction and long-term survival.

Ultrastructural Changes in Lung Allografts

Introduction Antibody mediated rejection (AMR) is a well-recognised cause of allograft injury; however only recently there is a growing recognition in lung transplantation (LTx). Allograft dysfunction can be multifactorial and challenges with C4d stain interpretation and the lack of specificity of histological criteria account for some of the difficulties in diagnosing pulmonary AMR. Donor Specific Antibodies (DSA) target the endothelium. In fact, in renal transplantation, endothelial activation markers and early ultrastructural changes of the endothelium correlate with AMR. The aim of this study was to identify ultrastructural changes in the endothelium of lung allografts in the presence of DSA, with the intent of determining if prospective use of electron microscopy might be helpful in establishing a diagnosis of AMR in LTx recipients. Materials & Methods The LTx database was queried for cases of pulmonary AMR between 07/2009 & 09/2015. The ISHLT guidelines were used to categorise these cases into definite, probable & possible AMR. Retrospective ultrastructural studies were performed on all these biopsies- either fresh or paraffin embedded. Cases of acute cellular rejection (4) and normal lung (3) were evaluated as controls. The findings on ultrastructural examination were correlated with the presence of DSA & diagnosis of AMR using the Pearson’s chi-square test of statistical significance. Results & Discussion Eleven patients (male, 54.5%) were included in this study.Mean age was 53yrs. Three cases were combined lung & heart Tx. We identified 7 cases of AMR (1 definite, 1 probable & 5 possible). The median time from LTx to biopsy (bx) was 210 days, with median follow up of 1063 days. Bronchiolitis Obliterans Syndrome was diagnosed in 5 patients. Ultrastructural studies were performed on 10 AMR bxs (pt 6:2 bxs; pt 7:3 bxs; all other pts: 1bx each), 4 ACR bxs & 4 controls. The results are shown.The presence of DSA as well as the ISHLT diagnosis of AMR significantly correlated with endothelial swelling, cytoplasmic vacuolisation & septal edema (p<0.01; each). Septal infiltration by neutrophils was only identified in AMR cases, although it did not achieve statistical significance. Importantly, these differences were still significant when using resin or paraffin based samples for EM, allowing larger retrospective studies to be performed; although endothelial swelling & vacuolisation occurred in non-DSA paraffin samples with EM.Conclusion Donor specific anti-HLA antibodies are associated with endothelial injury of the allograft. Ultrastructural findings such as endothelial swelling & vacuolization help in diagnosing antibody mediated allograft injury. Although paraffin embedded biopsy material can be used for this purpose, it is not without limitations and larger prospective studies are needed to validate these findings. The effect of DSA on the endothelial pathways will be important in all solid organ transplantation.

Impact on mid-term kidney graft outcomes of pretransplant anti-HLA antibodies detected by solid-phase assays: Do donor-specific antibodies tell the whole story?

The detrimental impact of preformed anti-HLA donor-specific antibodies (DSA) is well defined, contrarily to non-donor-specific antibodies (NDSA). We sought to evaluate their clinical impact in a cohort of 724 kidney graft recipients in whom anti-HLA antibodies were thoroughly screened and identified in pre-transplant sera by solid-phase assays. NDSA or DSA were detected in 100 (13.8%) and 47 (6.5%) recipients respectively, while 577 (79.7%) were non-allosensitized (NaS). Incidence of antibody-mediated rejection at 1-year was 0.7%, 4.0% and 25.5% in NaS, NDSA and DSA patients, respectively (NaS vs. NDSA P=0.004; NaS vs. DSA P<0.001; NDSA vs. DSA P<0.001). Graft survival was lowest in DSA (78.7%), followed by NDSA (88.0%) and NaS (93.8%) recipients (NaS vs. NDSA P=0.015; NaS vs. DSA P<0.001; NDSA vs. DSA P=0.378). Multivariable competing risk analysis confirmed both NDSA (sHR=2.19; P=0.025) and DSA (sHR=2.87; P=0.012) as significant predictors of graft failure. The negative effect of NDSA and DSA on graft survival was significant in patients receiving no induction (P=0.019) or an anti-IL-2 receptor antibody (P<0.001), but not in those receiving anti-thymocyte globulin (P=0.852). The recognition of the immunological risk associated with preformed DSA but also NDSA have important implications in patients’ risk stratification, and may impact clinical decisions at transplant.

Donor-specific antibodies and antibody-mediated rejection in vascularized composite allotransplantation.

The presence of donor-specific antibodies (DSA) increases the risk of graft failure. Although DSA characteristics, human leukocyte antigen class specificity, mean fluorescence intensity and immunoglobulin G subclasses, and their impact on the graft are quite well studied in solid organ transplants, very little information is known about their impact on vascularized composite allotransplantation (VCA). The aim of this review is to highlight recent publications regarding occurrence and effects of DSA, their follow-up and treatment in the field of VCA. The latest publications dealing with antibody-mediated rejection in VCA are mainly case presentations and reports embedded in reviews. The most important findings shown were the demonstration of the severe clinical impact of de-novo DSA and the urgent need of finding a therapeutic strategy for patients with acute antibody-mediated rejection. Suggested protocols for desensitization of possible candidates for reconstructive transplantation have been published, as these individuals are often highly sensitized and not appropriate patients for a standard surgical procedure because of their major tissue defects. The functional outcome of reconstructive transplantation has clearly exceeded the results achieved with conventional surgical techniques. The recipients' immune response, particularly development of DSA and the long-term adherence, which is probably associated with the occurrence of chronic rejection, remain a challenge.

Uncommon DR7-DR53-DQ haplotypes in four canadian subjects

Aim To describe uncommon DR7-DR53-DQ haplotypes in four Canadian subjects that deviate from the frequent common association between DR7, DR53 and DQ antigens. Methods Medium resolution HLA typing for HLA- DRB1, DRB3/4/5 and DQB1 loci were performed using Luminex based SSO kits (One Lambda Labtype). A high resolution typing using SSP for DRB4 (Olerup SSP kit) and SBT for DRB1 and DQB1 (Life Technologies) were further performed to evaluate these uncommon haplotypes. Results We detected presence of DRB4 ∗ 01:01 instead of more frequent DRB4 ∗ 01:03N in association with the DR7 and DQ9 haplotype in two Canadian subjects. Furthermore, we also detected DRB4 null allele in association with DR7 and DQ2 in a kidney transplant recipient and a bone marrow patient (Table 1). Conclusion Here, we report two cases of DRB1∗07, DRB4∗01, DQB1∗03:03 haplotype and two cases of DRB4∗01:03N null allele in association with DRB1 ∗ 07:01 and DQB1 ∗ 02:02 haplotype . Our findings are in disparity to reported common linkages in which DR7- DQ9 haplotype is commonly seen in association with the null allele DRB4 ∗ 01:03:01:02N . There are 15 alleles of DRB4; 12 of them produce an expressed DR53 antigen and 3 resulting in null alleles. The presence of these rare haplotypes might be due to unidirectional or bidirectional homologous recombination event that happened between the DR7, DR53, DQ2 and the DR7, DR53- null, DQ9 haplotypes. This is supported by the presence of reported DR7-DQ2 haplotype with a DRB4 null allele. It might also be due to point mutation in DRB4∗01:03:01 changing the splice site in case of DR7, DR53null, DQ2 haplotype. Understanding the genetics and expression of DRB4 gene is of clinical relevance in the hematopoetic stem cell transplant, both GVHD and graft rejection, in solid organ transplant especially effect of donor specific antibodies, and in disease association with autoimmune disorders, such as celiac, Crohn’s disease, myasthenia gravis, rheumatoid arthritis, Hashimoto’s thyroiditis, vitiligo, primary biliary cirrhosis and ALL in children. Download full-size image

Long-term Clinical Relevance of De Novo Donor-Specific Antibodies After Pediatric Liver Transplantation.

Anti-HLA antibodies and especially donor-specific antibodies (DSA) play a significant role in graft survival after solid organ transplantation. Their impact on long-term survival in adult liver transplantation (LT) is controversial, but they may be a risk factor. The effects of DSA after pediatric LT are still unclear. We performed a retrospective evaluation of DSA in sera from 43 children who had received transplants at our tertiary center. Twenty-four patients had good long-term clinical and laboratory graft function (group 1), whereas 19 LT recipients suffered from histologically confirmed and clinically relevant chronic allograft rejection (group 2); 16 of these have already undergone retransplantation due to graft dysfunction. Inclusion criteria were availability of sera before the first LT to identify preformed antibodies in case of DSA positivity after LT and long-term follow-up at our institution. Sera were analyzed for anti-HLA antibodies using Luminex single antigen beads, where a mean fluorescence intensity value of more than 1500 was considered positive. The prevalence of DSA was 33% for group 1 and 68% for group 2. Antibodies were predominantly HLA class II. Values of mean fluorescence intensity were comparable in both groups. Only one of the DSA+ ve patients from group 1 exhibited preformed antibodies. In conclusion, pediatric patients with chronic rejection revealed a higher rate of de novo DSA, especially of HLA-class II DSA. Further studies are necessary to confirm these data with a larger pediatric cohort.

An Anti-C1s Monoclonal, TNT003, Inhibits Complement Activation Induced by Antibodies Against HLA

Antibody-mediated rejection (AMR) of solid organ transplants (SOT) is characterized by damage triggered by donor-specific antibodies (DSA) binding donor Class I and II HLA (HLA-I and HLA-II) expressed on endothelial cells. While F(ab′)2 portions of DSA cause cellular activation and proliferation, Fc regions activate the classical complement cascade, resulting in complement deposition and leukocyte recruitment, both hallmark features of AMR. We characterized the ability of an anti-C1s monoclonal antibody, TNT003, to inhibit HLA antibody (HLA-Ab)-induced complement activation. Complement deposition induced by HLA-Ab was evaluated using novel cell- and bead-based assays. Human aortic endothelial cells (HAEC) were cultured with HLA-Ab and human complement; production of activated complement proteins was measured by flow cytometry. Additionally, C3d deposition was measured on single antigen beads (SAB) mixed with HLA-Ab and human complement. TNT003 inhibited HLA-Ab mediated complement deposition on HAEC in a concentration-dependent manner; C3a, C4a and C5a anaphylatoxin production was also diminished by TNT003. Finally, TNT003 blocked C3d deposition induced by Class I (HLAI-Ab)- and Class II (HLAII-Ab)-specific antibodies on SAB. These data suggest TNT003 may be useful for modulating the effects of DSA, as TNT003 inhibits complement deposition and split product formation generated by HLA-I/II-Ab in vitro.

(784) - Low Level Donor Specific Antibodies at Transplant Does Not Appear to Be Associated With the development of Cardiac Allograft Vasculopathy After Heart Transplantation

Donor specific antibodies (DSA) following heart transplant has been reported to be associated with increased development of cardiac allograft vasculopathy (CAV) and risk of mortality following transplantation. In the era of virtual crossmatch, we may now elect to place donor hearts in patients with low level DSAs that are not placed as avoids. The effect of these low level DSAs on the development of CAV has not yet been established.

Effect of donor-specific antibodies and panel reactive antibodies in living donor liver transplant recipients.

PurposePreformed circulating donor-specific antibodies (DSAs) immunologically challenge vascular endothelium and the bile duct. However, the liver is an immune-tolerant organ and can avoid immunological challenges. This study was undertaken to analyze the effects of DSAs after adult living donor liver transplantation (LDLT).MethodsWe retrospectively reviewed 219 LDLT patients' records treated at our center.ResultsOf the 219 patients, 32 (14.6%) were DSA (+) and 187 (85.4%) were DSA (-). Class I DSAs were present in 18 patients, class II in seven patients, and both in seven patients. Seven patients (3.2%) showed DSA to HLA-A, four (1.8%) to HLA-B, seven (3.2%) to HLA-DR, and 14 (6.4%) to two or more HLAs. More DSAs were observed in female recipients than male recipients in the DSA (+) group. The DSA (+) group showed significantly higher levels of class I and II panel reactive antibody (PRA) than did the DSA (-) group. No significant intergroup differences were found between incidences of primary nonfunction, acute rejection, vascular complication, or biliary complication. There were no significant differences in graft survival rates between the two groups. However, the recipients with multiple DSAs tended to have more acute rejection episodes and events of biliary stricture and lower graft survival rates than did patients in the DSA (-) group.ConclusionIn LDLT, the presence of multiple DSAs and high PRA seemed to be associated with poor graft outcomes, although our results did not reach statistical significance. Large cohort studies are necessary to clarify the impact of DSA and PRA in LDLT.

Pretransplant Donor-Specific Anti-HLA Antibodies and Their Characteristics Are Associated With Poorer Kidney Graft Outcomes in Kidney and Kidney-Pancreas Recipients.

The role of donor-specific antibodies (DSA) and their characteristics in kidney transplantation remains not fully understood. We aimed to analyze in a cohort of kidney and kidney-pancreas transplant recipients the effect of pretransplant DSA in kidney graft adverse outcomes: acute humoral rejection (AHR) and graft failure (GF). A cohort of 434 patients (pts) that received a kidney graft (67 pts also receiving a pancreas graft) between 2008-12 after a negative CDC crossmatch (XM) were included. Presence of anti-human leukocyte antigen (HLA) antibodies was investigated in pretransplant sera using a Luminex® screening assay and anti-HLA specificities were assigned performing a Luminex® single antigen assay [positive: mean fluorescence intensity (MFI) was ≥1000 (1K)]. In DSA+ pts, ROC curves were constructed to assess the ability of MFI values (DSAmax: highest DSA bead; DSAcum: detected DSA MFI sum) to predict AHR. Comparison between DSA defined groups:Table: No Caption available.1-year incidence of AHR by DSA class was 17%, 57% and 57%, in I (n=23), II (n=7) and I+II (n=7), respectively (logrank p=0.023); by DSA MFI was 6%, 46% and 67%, in 1k-3k (n=17), 3k-7k (n=11) and >7K (n=9), respectively (logrank p<0.001). Considering only DSA+ pts, comparisons were performed using χ2 or Mann-Whitney U test between AHR- (n=25) and AHR+ (n=12) groups. Differences were found in mean HLA mismatch (3.5 vs 4.3; p=0.008), median DSA number (1 vs 3; p=0.005), MFI DSAmax (2.5K vs 8K; p=0.001), DSAcum (3.5K vs 19.5K, p=0.001), DSAmax class II (12% vs 58%; p=0.006) and DSA class (AHR-: I 76%, II 12%, I+II 12%; p=0.02); number of kidney-pancreas (2 vs 2; p=0.6) and flow XM+ pts (2 vs 3; p=0.3) were similar. In ROC analysis, both MFI DSAmax (AUC 0.83; 3.75K had 92% sensitivity, 72% specificity) and DSAcum (AUC 0.85; 11.2K had 67% sensitivity, 92% specificity) were good predictors of AHR. Pretransplant DSA have a deleterious effect on kidney graft outcomes. Class, number and specially strength of DSA modulate that effect and should be considered in DSA+ pts management, such as the complementary behavior of MFI DSAmax and DSAcum as predictors of AHR.

Rat islets are not rejected by anti-islet antibodies in mice treated with costimulation blockade.

Costimulation blockade can prevent rejection of islet xenografts in naïve but not sensitized recipients. Donor-specific antibodies (DSA) may partly explain this observation. The effect of DSA on rat islet xenograft survival in mice receiving costimulation blockade was investigated. Naïve C57BL/6 mice with alloxan-induced diabetes were transplanted under the left kidney capsule with 100 Lewis rat islets. Recipients were divided into three groups receiving: (i) isotype control antibodies (Abs); (ii) anti-CD154 and CTLA4Ig; or (iii) anti-CD154, CTLA4Ig, and anti-LFA-1 every second day, day 0-8. At the time of transplantation (Tx), half of the animals in each group received naïve mouse serum and half xenoimmune serum derived from mice previously transplanted with rat islets. Non-fasting blood glucose levels and body weight were followed daily. Cured mice were examined by intraperitoneal glucose tolerance (IPGT) tests at 1 and 4 months after transplantation. Donor-specific antibodies were detected in immune serum-injected recipients up to at least 96 h post-Tx. Short term (≤96 h), there was no significant difference with regard to graft mass, infiltrating and apoptotic cells between groups of mice receiving naïve and immune sera. A moderate infiltration of polymorphonuclear and mononuclear cells was seen 96 h post-Tx in mice given control Abs, whether or not they received immune or naïve mouse serum. Mice given costimulation blockade had well-maintained endocrine tissue and very little cell infiltration. There was no significant difference in islet xenograft function and survival long term between groups receiving naïve and immune sera in combination with costimulation blockade. About half of the mice receiving costimulation blockade lost graft function within 110 days. The presence at Tx of DSA does not appear to negatively influence early and late islet xenograft survival in mice receiving costimulation blockade.

Sustained Donor Engraftment in Recipients of Double-Unit Cord Blood Transplantation Is Possible Despite Donor-Specific Human Leukoctye Antigen Antibodies

The impact of human leukocyte antigen (HLA) donor-specific antibodies (DSA) on cord blood (CB) engraftment is controversial. We evaluated the influence of pre-existing HLA-antibodies (HLA-Abs) on engraftment in 82 double-unit CB recipients (median age, 48 years) who underwent transplantation for hematologic malignancies. Of 28 patients (34%) with HLA-Abs, 12 had DSA (median mean fluorescence intensity 5255; range, 1057 to 9453). DSA patients had acute leukemia (n = 11) or myelodysplasia (n = 1) and all received either high-dose or reduced-intensity (but myeloablative) conditioning. After myeloablative CB transplantation (CBT) (n = 67), sustained donor engraftment was observed in 95% without HLA-Abs (median, 23 days), 100% with nonspecific HLA-Abs (median, 23 days), and 92% with DSA (median, 31 days, P = .48). Of 6 patients with HLA-Abs to 1 unit, 3 engrafted with that unit and 3 with the other. Of 6 patients with HLA-Abs against both units, 1 had graft failure despite being 100% donor, and 5 engrafted with 1 unit. Successful donor engraftment is possible in patients with DSA after myeloablative double-unit CBT. Our data suggest potential deleterious effects of DSA can be abrogated in patients with hematologic malignancies.

Pre-transplant donor specific anti-HLA antibody is associated with antibody-mediated rejection, progressive graft dysfunction and patient death

BackgroundThe long term effect of donor specific antibodies (DSA) detected by Luminex Single Antigen Bead (SAB) assay in the absence of a positive complement-dependant cytotoxicity (CDC) crossmatch is unclear.DSA at the time of transplant were determined retrospectively in 258 renal transplant recipients from 2003 to 2007 and their relationship with rejection and graft function prospectively evaluated.After a median of 5.6years follow-up 9% of patients had antibody mediated rejection (AMR) (DSA 11/37 (30%), DSA-Neg 13/221 (6%), HR 6.6, p<0.001). Patients with anti-HLA class II (HR 6.1) or both class I+II (HR 10.1) DSA had the greatest risk for AMR. The Mean Fluorescent Intensity (MFI) of the DSA was significantly higher in patients with AMR than those with no rejection (p=0.006). Moreover, the strength of the antibody was shown to be important, with the risk of AMR significantly greater in those with DSA >8000 MFI than those with DSA <8000 MFI (HR 23, p<0.001).eGFR progressively declined in patients with DSA but was stable in those without DSA (35.7±20.4mls/min vs 48.5±22.7) and composite patient and graft survival was significantly worse in those with class II (HR 2.9) or both class I+II (HR 3.7) but not class I DSA. Class II DSA alone, or in combination with class I DSA had the strongest association with graft loss and patient death.Patients with DSA not only have increased rates of acute AMR, but also chronic graft dysfunction, graft loss and death. Antibody burden quantified by SAB assay may identify patients at highest immunological risk and therefore influence patient management and improve long-term patient outcome.