Impact of Transient and Persistent Donor-Specific Antibodies in Lung Transplantation.

Lung transplantation (LuTx) is an established treatment for patients with end-stage lung diseases, however, outcomes are limited by acute and chronic rejection. One aspect that has received increasing attention is the role of the host's humoral alloresponse, particularly the formation of de novo donor-specific antibodies (dnDSAs). The aim of this study was to investigate the clinical significance of transient and persistent dnDSAs and to understand their impact on outcomes after LuTx. A retrospective analysis was conducted using DSA screening data from LuTx recipients obtained at the Medical University of Vienna between February 2016 and March 2021. Of the 405 LuTx recipients analyzed, 205 patients developed dnDSA during the follow-up period. Among these, 167 (81%) had transient dnDSA and 38 (19%) persistent dnDSA. Persistent but not transient dnDSAs were associated with chronic lung allograft dysfunction (CLAD) and antibody-mediated rejection (AMR) (p < 0.001 and p = 0.006, respectively). CLAD-free survival rates for persistent dnDSAs at 1-, 3-, and 5-year post-transplantation were significantly lower than for transient dnDSAs (89%, 59%, 56% vs. 91%, 79%, 77%; p = 0.004). Temporal dynamics of dnDSAs after LuTx have a substantial effect on patient outcomes. This study underlines that the persistence of dnDSAs poses a significant risk to graft and patient survival.

Deceased-Donor Acute Kidney Injury and Acute Rejection in Kidney Transplant Recipients: A Multicenter Cohort.

RATIONALE & OBJECTIVE: Donor acute kidney injury (AKI) activates innate immunity, enhances HLA expression in the kidney allograft, and provokes recipient alloimmune responses. We hypothesized that injury and inflammation that manifested in deceased-donor urine biomarkers would be associated with higher rates of biopsy-proven acute rejection (BPAR) and allograft failure after transplantation. STUDY DESIGN: Prospective cohort. SETTING & PARTICIPANTS: 862 deceased donors for 1,137 kidney recipients at 13 centers. EXPOSURES: We measured concentrations of interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) in deceased donor urine. We also used the Acute Kidney Injury Network (AKIN) criteria to assess donor clinical AKI. OUTCOMES: The primary outcome was a composite of BPAR and graft failure (not from death). A secondary outcome was the composite of BPAR, graft failure, and/or de novo donor-specific antibody (DSA). Outcomes were ascertained in the first posttransplant year. ANALYTICAL APPROACH: Multivariable Fine-Gray models with death as a competing risk. RESULTS: Mean recipient age was 54 ± 13 (SD) years, and 82% received antithymocyte globulin. We found no significant associations between donor urinary IL-18, KIM-1, and NGAL and the primary outcome (subdistribution hazard ratio [HR] for highest vs lowest tertile of 0.76 [95% CI, 0.45-1.28], 1.20 [95% CI, 0.69-2.07], and 1.14 [95% CI, 0.71-1.84], respectively). In secondary analyses, we detected no significant associations between clinically defined AKI and the primary outcome or between donor biomarkers and the composite outcome of BPAR, graft failure, and/or de novo DSA. LIMITATIONS: BPAR was ascertained through for-cause biopsies, not surveillance biopsies. CONCLUSIONS: In a large cohort of kidney recipients who almost all received induction with thymoglobulin, donor injury biomarkers were associated with neither graft failure and rejection nor a secondary outcome that included de novo DSA. These findings provide some reassurance that centers can successfully manage immunological complications using deceased-donor kidneys with AKI.

Monitoring of Serological, Cellular and Genomic Biomarkers in Transplantation, Computational Prediction Models and Role of Cell-Free DNA in Transplant Outcome.

The process and evolution of an organ transplant procedure has evolved in terms of the prevention of immunological rejection with the improvement in the determination of immune response genes. These techniques include considering more important genes, more polymorphism detection, more refinement of the response motifs, as well as the analysis of epitopes and eplets, its capacity to fix complement, the PIRCHE algorithm and post-transplant monitoring with promising new biomarkers that surpass the classic serum markers such as creatine and other similar parameters of renal function. Among these new biomarkers, we analyze new serological, urine, cellular, genomic and transcriptomic biomarkers and computational prediction, with particular attention to the analysis of donor free circulating DNA as an optimal marker of kidney damage.

Tacrolimus variability is associated with de novo donor-specific antibody development in pediatric renal transplant recipients.

BACKGROUND: Donor-specific antibody (DSA) is a risk factor for antibody-mediated rejection and shortened graft survival. We investigated the role of intrapatient variability in tacrolimus trough levels on graft outcomes (i.e., de novo DSA, rejection, graft loss) in pediatric renal transplant recipients. METHODS: This was a single-center retrospective study which included 38 pediatric renal transplant recipients. Intrapatient tacrolimus variability was defined using the coefficient of variation (CV; SD/Mean × 100) for all levels obtained after 3 months post-transplant. CV cut-points of 30%, 40%, and 50% were used in the analyses. RESULTS: The median CV 43.1% (35.0%, 58.6%). Out of 38 patients, 19 (50%) developed de novo DSA. In the logistic regression model, after adjusting for age, rejection history, maintenance immunosuppression, and CV, for every 10% increase in tacrolimus variability, the odds of developing de novo DSA increased by 53% (p = 0.048, CI 1.0005, 1.11). Age at transplant was also an independent risk factor for DSA development; every 1 year increase in age was associated with a 31% increase in the odds of developing DSA (p = 0.03, CI 1.03, 1.67). At a CV cut-point ≥ 30%, higher tacrolimus variability was associated with an increased incidence of allograft rejection (0% vs 42%, < 30 and ≥ 30% respectively, p = 0.07). As there were few graft loss events (n = 4) in our study population, an association could not be determined between tacrolimus variability and graft loss. CONCLUSION: Tacrolimus variability and age at transplant were identified as independent risk factors for de novo DSA development. There was an association between tacrolimus variability and rejection in pediatric renal transplant recipients. Adding the assessment of tacrolimus variability to current monitoring methods may be an important step towards improving graft outcomes.

Non-HLA-matched 3rd party vascular allograft in renal transplant may lead to sensitization against donor HLA.

3rd party donor vessels are often used for vascular reconstruction in organ transplantation. While current practice ensures that 3rd party vessels are blood group matched, HLA matching to the non-intended recipient is not performed. This practice potentially sensitizes the recipient and may reduce their future chance of renal transplant from a larger pool of donors. We examined our cohort of renal transplant recipients who received non-HLA-matched 3rd party vessels for the de-novo development of donor-specific HLA antibodies. Our institution's Human Tissue Authority (HTA) blood vessel registers were examined to identify stored donor vessels and their non-intended recipients. Donor vessel HLA status was cross-referenced with the recipient HLA status. Between 2004 and 2014, five patients were identified that received 3rd party non-HLA-matched vessels for vascular reconstruction during renal transplantation. Three patients (60%) subsequently developed donor-specific HLA antibodies. These data provide evidence that use of non-HLA-matched stored 3rd party vascular grafts may lead to sensitization in the recipient. Where time permits, HLA matching should be performed to avoid this allogeneic response. Laboratories monitoring DSA should be aware of any patient receiving a non-HLA-matched 3rd party vascular graft, and recipients may benefit from increased post-transplant immunological vigilance.

Humoral Immune Response and Allograft Function in Kidney Transplantation.

HLA antibodies can damage a kidney transplant. In January 2013, consensus guidelines from The Transplantation Society were published regarding technical aspects of HLA antibody determination, as well as their potential significance in the pre- and posttransplantation periods. During the past 2 years, new studies have been reported, but controversies remain. In this article, these new data related to HLA antibodies in kidney transplantation are reviewed and compared to relevant prior research. Pretransplantation sensitization issues are discussed, including the new more sensitive assays (flow cytometry and solid-phase immunoassays such as Luminex single-antigen bead assays). A positive complement-dependent cytotoxicity crossmatch remains an absolute contraindication to transplantation, although a positive flow cytometry crossmatch is only a relative contraindication. Positivity only by solid-phase assays increases the risk for acute rejection and transplant loss, but acceptable cutoffs are not defined. The sensitizing effect of red blood cell transfusions is substantiated. Following allograft failure, continued immunosuppression decreases the risk of sensitization, whereas overall, the effect of nephrectomy remains uncertain. Regarding the posttransplantation period, new data are available concerning the timing and significance of donor-specific antibodies (DSA). Whereas some centers report DSA appearance after years, others detect DSA within months. The prominence of class II DSA, especially DQ, in the posttransplantation period is noted. The relevance of non-HLA antibodies is discussed, including anti-endothelial cell antibodies, major histocompatibility complex class I chain-related protein A antibodies, and angiotensin II type 1 receptor autoantibodies.

Challenges and opportunities for designing clinical trials for antibody mediated rejection.

Significant progress has been made in kidney transplantation, with 1-year graft survival nearing 95%. However, long-term allograft survival remains suboptimal, with a 10-year overall graft survival rate of only 53.6% for deceased donor transplant recipients. Chronic active antibody-mediated rejection (ABMR) is a leading cause of death-censored graft loss, yet no therapy has demonstrated efficacy in large, randomized trials, despite substantial investment from pharmaceutical companies. Several clinical trials aimed to treat chronic ABMR in the past decade have yielded disappointing results or were prematurely terminated, attributed to factors including incomplete understanding of disease mechanisms, heterogeneous patient populations with comorbidities, slow disease progression, and limited patient numbers. This review aims to discuss opportunities for improving retrospective and prospective studies of ABMR, focusing on addressing heterogeneity, outcome measurement, and strategies to enhance patient enrollment to inform study design, data collection, and reporting.

A gentler approach to monitor for heart transplant rejection.

Despite developments in circulating biomarker and imaging technology in the assessment of cardiovascular disease, the surveillance and diagnosis of heart transplant rejection has continued to rely on histopathologic interpretation of the endomyocardial biopsy. Increasing evidence shows the utility of molecular evaluations, such as donor-specific antibodies and donor-derived cell-free DNA, as well as advanced imaging techniques, such as cardiac magnetic resonance imaging, in the assessment of rejection, resulting in the elimination of many surveillance endomyocardial biopsies. As non-invasive technologies in heart transplant rejection continue to evolve and are incorporated into practice, they may supplant endomyocardial biopsy even when rejection is suspected, allowing for more precise and expeditious rejection therapy. This review describes the current and near-future states for the evaluation of heart transplant rejection, both in the settings of rejection surveillance and rejection diagnosis. As biomarkers of rejection continue to evolve, rejection risk prediction may allow for a more personalized approach to immunosuppression.

Anti-complement 5 antibody ameliorates antibody-mediated rejection after liver transplantation in rats.

Antibody-mediated rejection (AMR) remains a refractory rejection after donor-specific antibody (DSA)-positive or blood-type incompatible liver transplantation (LT), even in the era of pre-transplant rituximab desensitization. This is due to the lack of not only effective post-transplant treatments but also robust animal models to develop/validate new interventions. Orthotopic LT from male Dark Agouti (DA) to male Lewis (LEW) rats was used to develop a rat LT-AMR model. LEW were pre-sensitized by a preceding skin transplantation from DA 4-6 weeks before LT (Group-PS), while sham procedure was performed in non-sensitized controls (Group-NS). Tacrolimus was daily administered until post-transplant day (PTD)-7 or sacrifice to suppress cellular rejections. Using this model, we validated the efficacy of anti-C5 antibody (Anti-C5) for LT-AMR. Group-PS+Anti-C5 received Anti-C5 intravenously on PTD-0 and -3. Group-PS showed increased anti-donor (DA) antibody-titers (P <0.001) and more C4d deposition in transplanted livers than in Group-NS (P <0.001). Alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bile acid (TBA), and total bilirubin (T-Bil) were all significantly higher in Group-PS than in Group-NS (all P <0.01). Thrombocytopenia (P <0.01), coagulopathies (PT-INR, P =0.04), and histopathological deterioration (C4d+h-score, P <0.001) were also confirmed in Group-PS. Anti-C5 administration significantly lowered anti-DA IgG (P <0.05), resulting in decreased ALP, TBA, and T-Bil on PTD-7 than in Group-PS (all P <0.01). Histopathological improvement was also confirmed on PTD-1, -3, and -7 (all P <0.001). Of the 9,543 genes analyzed by RNA sequencing, 575 genes were upregulated in LT-AMR (Group-PS vs. Group-NS). Of these, 6 were directly associated with the complement cascades. In particular, Ptx3, Tfpi2, and C1qtnf6 were specific to the classical pathway. Volcano plot analysis identified 22 genes that were downregulated by Anti-C5 treatment (Group-PS+Anti-C5 vs. Group-PS). Of these, Anti-C5 significantly down-regulated Nfkb2, Ripk2, Birc3, and Map3k1, the key genes that were amplified in LT-AMR. Notably, just two doses of Anti-C5 only on PTD-0 and -3 significantly improved biliary injury and liver fibrosis up to PTD-100, leading to better long-term animal survival (P =0.02). We newly developed a rat model of LT-AMR that meets all the Banff diagnostic criteria and demonstrated the efficacy of Anti-C5 antibody for LT-AMR.

Variability in Donor-Derived Cell-Free DNA Scores to Predict Mortality in Heart Transplant Recipients - A Proof-of-Concept Study.

BACKGROUND: Over the last decade, expanding use of molecular diagnostics in heart transplantation has allowed implementation of non-invasive surveillance strategies for monitoring allograft health. The commercially available HeartCare platform combines the AlloMap gene expression profiling assay and the AlloSure donor-derived cell-free DNA test (dd-cfDNA). Beyond their established use for assessment of rejection, evidence is building for predictive utility, with the longitudinal AlloMap Variability score previously shown to correlate with the risk of future rejection, graft dysfunction, re-transplantation, or death. In this single-center, retrospective pilot study, we evaluated the performance of a novel AlloSure Variability metric in predicting mortality in a cohort of heart transplant recipients. METHODS: Seventy-two adult heart transplant recipients with at least 3 concurrent AlloMap/AlloSure results were included. Demographic, clinical, imaging, and laboratory parameters were captured. Variability was defined as the standard deviation of longitudinal AlloMap/AlloSure results. A Cox multivariable adjusted proportional hazards model was used to evaluate the variability metrics as predictors of mortality. Associations between AlloMap/AlloSure variability and donor specific antibody (DSA) status were also assessed. RESULTS: A total of 5 patients (6.9%) died during a median follow-up of 480 days. In a univariate Cox proportional hazards model, higher AlloSure variability (HR 1.66, 95%CI 1.14 - 2.41), but not AlloMap variability or the cross-sectional AlloSure/AlloMap results was associated with increased mortality risk. Longitudinal AlloSure variability was also higher among patients with both preformed DSA and those developing de novo DSA. CONCLUSION: Our results suggest that increased variability of dd-cfDNA in heart transplant patients is associated with both mortality risk and the presence of donor specific antibodies. These findings highlight the added value of longitudinal data in the interpretation of AlloMap/AlloSure scores in this population and open the door to larger studies investigating the utility of these metrics in shaping post-transplant clinical care paradigms.

Living Donor Kidney Transplantation in Patients With Donor-Specific HLA Antibodies After Desensitization With Immunoadsorption.

Due to the current organ shortage, living donor kidney transplantation is increasingly performed across HLA (human leukocyte antigen) or ABO antibody barriers. There is still uncertainty about the risk of antibody-mediated rejection (AMR) episodes, which may limit long-term graft survival. From March 2007 to December 2016, 58 sensitized living donor kidney transplant candidates were identified and 38 patients eventually included in the study: 36 patients (95%) had pre-transplant and pre-desensitization Luminex-detected donor-specific HLA antibodies (DSA), and 17/36 patients (47%) in addition had a positive crossmatch result. Two patients had no detectable DSA but a positive CDC B-cell crossmatch result. Patients were treated with pre- and post-transplant apheresis and powerful immunosuppression including the anti-CD20 antibody rituximab (N = 36) in combination with thymoglobulin (N = 20) or anti-IL2 receptor antibody (N = 18). The results of the 38 successfully desensitized and transplanted patients were retrospectively compared to the results of 76 matched standard-risk recipients. Desensitized patients showed patient and graft survival rates similar to that of standard-risk recipients (P = 0.55 and P = 0.16, respectively). There was a trend toward reduced death-censored graft survival in desensitized patients (P = 0.053) which, however, disappeared when the 34 patients who were transplanted after introduction of sensitive Luminex testing were analyzed (P = 0.43). The incidence of rejection episodes without borderline changes were in desensitized patients with 21% similar to the 18% in standard-risk patients (P = 0.74). Thirty-six patients had pre-transplant HLA class I and/or II DSA that were reduced by 85 and 81%, respectively, during pre-transplant desensitization (P < 0.001 for both). On day 360 after transplantation, 20 of 36 (56%) patients had lost their DSA. The overall AMR rate was 6% in these patients, but as high as 60% in 5 (14%) patients with persistent and de novo DSA during year 1; 2 (40%) of whom lost their graft due to AMR. Eleven (31%) patients with persistent DSA but without de novo DSA had an AMR rate of 18% without graft loss while one patient lost her graft without signs of AMR. Our desensitization protocol for pre-sensitized living donor kidney transplant recipients with DSA resulted in good graft outcomes with side effects and rejection rates similar to that of standard-risk recipients. Adequate patient selection prior to transplantation and frequent immunological monitoring thereafter is critical to minimize rejection episodes and subsequent graft loss.

Allo-Specific Humoral Responses: New Methods for Screening Donor-Specific Antibody and Characterization of HLA-Specific Memory B Cells.

Antibody-mediated allograft rejection (AMR) causes more kidney transplant failure than any other single cause. AMR is mediated by antibodies recognizing antigens expressed by the graft, and antibodies generated against major histocompatibility complex (MHC) mismatches are especially problematic. Most research directed towards the management of clinical AMR has focused on identifying and characterizing circulating donor-specific HLA antibody (DSA) and optimizing therapies that reduce B-cell activation and/or block antibody secretion by inhibiting plasmacyte survival. Here we describe a novel set of reagents and techniques to allow more specific measurements of MHC sensitization across different animal transplant models. Additionally, we have used these approaches to isolate and clone individual HLA-specific B cells from patients sensitized by pregnancy or transplantation. We have identified and characterized the phenotypes of individual HLA-specific B cells, determined the V(D)J rearrangements of their paired H and L chains, and generated recombinant antibodies to determine affinity and specificity. Knowledge of the BCR genes of individual HLA-specific B cells will allow identification of clonally related B cells by high-throughput sequence analysis of peripheral blood mononuclear cells and permit us to re-construct the origins of HLA-specific B cells and follow their somatic evolution by mutation and selection.

Efficacy and Safety of Iguratimod Supplement to the Standard Immunosuppressive Regimen in Highly Mismatched Renal Transplant Recipients: A Pilot Study.

Iguratimod (IGU) can mitigate the symptoms of rheumatoid arthritis through its anti-inflammatory effects. The objective of this study was to investigate the clinical efficacy and safety of IGU in highly HLA-mismatched renal transplant recipients, in combination with standard immunosuppressive regimen. This pilot study was designed as an open-label, blank-control, randomized clinical trial on patients recruited from a single transplant center in China. Patients who met the inclusion criteria were randomized to the IGU (n=27) and blank control (n=27) groups. IGU was administrated with the conventional triple immunosuppressive protocol for 52 weeks after kidney transplantation. The incidence of biopsy-proven acute rejection rate was 14.8% (4/27) in the IGU group and 29.6% (8/27) in the control group, P = 0.19. The clinical rejection rate was also substantially reduced in the IGU group (3.7% vs. 18.5%, P = 0.08). De novo donor-specific antibody also showed a decline trend in the IGU group after 52 weeks. The graft function and incidence of adverse events were similar between the two groups. In addition, IGU intervention significantly decreased the number of NK cells throughout the follow-up. In conclusion, our study has shown the possibility that IGU could reduce the allograft rejection rate and de novo DSA with appreciable safety in combination with conventional immunosuppressants. Formal clinical trials were warranted based on current findings.

Current Approaches to Desensitization in Solid Organ Transplantation.

Major advancements in the development of HLA antibody detection techniques and our understanding of the outcomes of solid organ transplant in the context of HLA antibody have occurred since the relevance of sensitization was first recognized nearly 50 years ago. Additionally, kidney paired donation programs (KPD) have become widespread, deceased donor allocation policies have changed, and several new therapeutic options have become available with promise to reduce HLA antibody. In this overview we aim to provide thoughtful guidance about when desensitization in kidney transplantation should be considered taking into account the outcomes of HLA incompatible transplantation. Novel therapeutics, desensitization endpoints, and strategies for future study will also be discussed. While most of our understanding about desensitization comes from studying kidney transplant candidates and recipients, many of the concepts discussed can be easily applied to desensitization in all of solid organ transplantation.

Highly Sensitized Patients Are Well Served by Receiving a Compatible Organ Offer Based on Acceptable Mismatches.

Highly sensitized kidney patients accrue on the transplant waiting list due to their broad immunization against non-self Human Leucocyte Antigens (HLA). Although challenging, the best option for highly sensitized patients is transplantation with a crossmatch negative donor without any additional therapeutic intervention. The Eurotransplant Acceptable Mismatch (AM) program was initiated more than 30 years ago with the intention to increase the chance for highly sensitized patients to be transplanted with such a compatible donor. The AM program allows for enhanced transplantation to this difficult to transplant patient group by allocating deceased donor kidneys on the basis of a match with the recipient's own HLA antigens in combination with predefined acceptable antigens. Acceptable antigens are those HLA antigens towards which the patients has never formed antibodies, as determined by extensive laboratory testing. By using this extended HLA phenotype for allocation and giving priority whenever a compatible donor organ becomes available, organ offers are made for roughly 80% of patients in this program. Up till now, more than 1700 highly sensitized patients have been transplanted through the AM program. Recent studies have shown that the concept of acceptable mismatches being truly immunologically acceptable holds true for both rejection rates and long-term graft survival. Patients that were transplanted through the AM program had a similar rejection incidence and long-term graft survival rates identical to non-sensitized patients transplanted through regular allocation. However, a subset of patients included in the AM program does not receive an organ offer within a reasonable time frame. As these are often patients with a rare HLA phenotype in comparison to the Eurotransplant donor population, extension of the donor pool for these specific patients through further European collaboration would significantly increase their chances of being transplanted. For those patients that will not benefit from such strategy, desensitization is the ultimate solution.

Effect of Optimized Immunosuppression (Including Rituximab) on Anti-Donor Alloresponses in Patients With Chronically Rejecting Renal Allografts.

RituxiCAN-C4 combined an open-labeled randomized controlled trial (RCT) in 7 UK centers to assess whether rituximab could stabilize kidney function in patients with chronic rejection, with an exploratory analysis of how B cell-depletion influenced T cell anti-donor responses relative to outcome. Between January 2007 and March 2015, 59 recruits were enrolled after screening, 23 of whom consented to the embedded RCT. Recruitment was halted when in a pre-specified per protocol interim analysis, the RCT was discovered to be significantly underpowered. This report therefore focuses on the exploratory analysis, in which we confirmed that when B cells promoted CD4+ anti-donor IFNγ production assessed by ELISPOT, this associated with inferior clinical outcome; these patterns were inhibited by optimized immunosuppression but not rituximab. B cell suppression of IFNγ production, which associated with number of transitional B cells and correlated with slower declines in kidney function was abolished by rituximab, which depleted transitional B cells for prolonged periods. We conclude that in this patient population, optimized immunosuppression but not rituximab promotes anti-donor alloresponses associated with favorable outcomes. Clinical Trial Registration: Registered with EudraCT (2006-002330-38) and www.ClinicalTrials.gov, identifier: NCT00476164.

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

BACKGROUND: The 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 5.6 years 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 ± 20.4 mls/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.

Peri-operative third party red blood cell transfusion in renal transplantation and the risk of antibody-mediated rejection and graft loss.

Historic red blood cell transfusion (RBCT) may induce anti-HLA antibody which, if donor specific (DSA), is associated with increased antibody-mediated rejection (AMR). Whether post-operative RBCT influences this risk is unknown. We examined the RBCT history in 258 renal transplant recipients stratified according to prevalent recipient HLA antibody (DSA, Non-DSA or No Antibody). AMR occurred more frequently in patients who received RBCT both pre and post transplant compared with all other groups (Pre+Post-RBCT 21%, Pre-RBCT 4%, Post-RBCT 6%, No-RBCT 6%, HR 4.1 p=0.004). In the 63 patients who received Pre+Post-RBCT, 65% (13/20) with DSA developed AMR compared with 0/6 in the Non-DSA group and 2/37 (5%) in the No-Antibody group (HR 13.9 p<0.001). In patients who received No-RBCT, Pre-RBCT or Post-RBCT there was no difference in AMR between patients with DSA, Non-DSA or No-Antibody. Graft loss was independently associated with Pre+Post-RBCT (HR 6.5, p=0.001) AMR (HR 23.9 p<0.001) and Non-AMR (6.0 p=0.003) after adjusting for DSA and delayed graft function. Re-exposure to RBCT at the time of transplant is associated with increased AMR only in patients with preformed DSA, suggesting that RBCT provides additional allostimulation. Patients receiving Pre+Post-RBCT also had an increased risk of graft loss independently of AMR or DSA. Both pre and post procedural RBCT in renal transplantation is associated with modification of immunological risk and warrants additional study.