Antibody-mediated Rejection Research Articles

Epidemiology of Infections in Lung Transplant Recipients Treated With Belatacept.

Belatacept is a costimulatory blocker that can be used to prevent and treat rejection in lung transplant recipients (LuTRs). The epidemiology of infections in belatacept-treated LuTRs has not been systematically evaluated. We performed a single-center retrospective study of all adult LuTRs who received belatacept as prevention or treatment of antibody-mediated rejection (desensitization) or as part of maintenance immunosuppression from January 1, 2011, to June 30, 2022. We assessed the epidemiology of infections that occurred within 12 months following the first belatacept dose. Fifty-two LuTRs received at least one dose of belatacept as either desensitization (n = 32) or maintenance immunosuppression (n = 20). Among 45 patients who were cytomegalovirus (CMV) donor and/or recipient seropositive, nine (20%) developed CMV infection. Seven (77%) CMV infections occurred despite valganciclovir prophylaxis and four (44%) were associated with antiviral resistance. Three (6%) LuTRs developed Epstein-Barr virus (EBV) associated post-transplant lymphoproliferative disorder (PTLD). Twenty-five (48%) LuTRs developed 43 bacterial infections and five (10%) developed proven or probable invasive fungal disease. Incidence rates of viral, bacterial, and fungal infections were similar between the desensitization and maintenance groups: incidence rate ratios (95% confidence interval) were 0.70 (0.32-1.57), 1.31 (0.70-2.46), and 2.82 (0.31-25.2), respectively. Infection/PTLD prompted belatacept discontinuation in eight (15%) patients. In the first year after belatacept initiation, LuTRs commonly developed CMV infections, EBV+ PTLD, and bacterial infections. Multicenter collaborations are needed to better understand infection risks in LuTRs treated with belatacept.

Non-HLA Autoantibodies Against Angiotensin II Receptor 1 (AT1R) and Endothelin A Receptor (ETAR) in Pediatric Kidney Transplantation

Antibody-mediated rejection (AMR) is the leading cause of premature kidney transplant failure. The role of alloantibodies against Human Leukocyte Antigens (HLA) has been a primary focus in AMR. More recently autoantibodies and alloantibodies against the angiotensin II receptor type 1 (AT1R) and the endothelin A receptor (ETAR) have been linked to poor allograft outcomes in kidney transplantation. Nevertheless, evidence supporting routine testing remains insufficient. ELISA testing for anti-AT1R and anti-ETAR antibodies was performed in a pediatric renal transplant cohort. We selected 12 pediatric recipients who had undergone protocol biopsies and antibody measurements at 6 and 24 months post-transplant. Immunohistochemistry was performed on biopsies for AT1R and ETAR as well as the adhesion molecules ICAM-1 and VCAM-1. The analysis showed that ICAM-1 and VCAM-1 expression was significantly increased, along with the presence of circulating antibodies, in patients at 24 months post-transplant compared to patients without circulating antibodies. The presence of anti-AT1R and anti-ETAR antibodies does not seem to influence the expression of their receptors in the transplanted organ. Instead, the increase in adhesion molecules may precede the development of histological damage. Therefore, enlarging the cohort and extending long-term observation would help to understand the impact of anti-AT1R and anti-ETAR antibodies after transplantation.

Heart Transplant Rejection in the Setting of Glyphosate Herbicide Exposure; A Case Report

Glyphosate is a common herbicide utilized worldwide with known exposure related toxicities. Numerous adverse effects related to glyphosate exposure have been documented, specifically in non-human models, however literature is lacking on cardiotoxic effects specific to heart transplant patients. Rejection is the most common post-transplant complication and the diagnosis of such is vital in order to guide immediate and appropriate treatment. In addition to the endomyocardial biopsy, noninvasive genetic testing can aid in rejection diagnosis and distinguish between cell-mediated and antibody-mediated rejection. We describe a case of glyphosate exposure in a post orthotopic heart transplant and the subsequent heart transplant rejection, patient’s clinical course, treatment, and follow up.

PIRCHE-II: a new tool to predict rejection in cardiac transplantation?

Abstract Aim This retrospective observational study aims to compare patients diagnosed with antibody-mediated or cell-mediated rejection with patients without episodes of rejection and study any predictors of rejection at follow-up with particular attention to PIRCHE-II scores. Materials and Methods We performed a retrospective evaluation of prospectively collected data of heart transplant patients from January 2022 to August 2023, at a single hospital. Preoperative, intraoperative and postoperative parameters are collected anonymously in our institutional database used for internal quality control. The primary endpoint was the incidence of rejection in one of three control endomyocardial biopsies. As pre-operative data, age, sex, BSA, blood group mismatch, risk such as dyslipidemia, hypertension, diabetes, peripheral vascular disease, COPD, previous cardiac surgery, PRA, ischemia time and post-operative infections. We evaluated patients at a mean follow-up of 106 (78 – 180) days. In patients who tested positive for cell-mediated or antibody-mediated rejection, the PIRCHE-II score was calculated. Results There were 45 patients with no diagnosis of rejection and they were aged 61 [50-65]; 22.2% were women, with a mean BSA of 1.87 ± 0.19. 22.2% had a blood type mismatch. They had a mean PIRCHE-II of 111.88 ± 43.6. There were 15 patients diagnosed with rejection and they were 63 years old [52 – 66]; 20.0% were women, with a mean BSA of 1.84 ± 0.23. 13.3% had a blood type mismatch. They had a mean PIRCHE-II of 113.70 ± 33.90. In multivariable analysis, the main predictors of rejection were plasma transfusions [OR 0.053, 95% CI, p=0.02], post-operative infections [OR 0.076, 95% CI, p=<0, 02] and the PIRCHE – II [OR 3.284, 95% CI, p=0.04]. The mean PIRCHE-II of patients who presented antibody-mediated or cell-mediated rejection was 113.70 ± 33.90 and that of patients who did not present any rejection was 111.88 ± 33.90; Conclusion According to the results obtained, the PIRCHE-II algorithm could be a tool in immunological risk stratification in patients undergoing cardiac transplantation. It is necessary, however, to apply PIRCHE-II to a larger number of patients and should also be considered in light of other factors such as the immunological status of the recipients, the immediate post-operative course (infections, CMV reactivation, blood component transfusions), which could constitute an immunological trigger and patient compliance in immunosuppressive therapy.Patients' featuresResuts

Role of pericoronary adipose tissue inflammation at CCTA after heart transplantation as non-invasive diagnostic tool of cardiac rejection and predictor of major adverse cardiovascular events

Abstract Background Long-term survival of heart transplanted (HT) patients is challenged by cardiac rejection and cardiac allograft vasculopathy (CAV). Until now, there are no established biomarkers for graft dysfunction, and the conventional approach for cardiac rejection surveillance is through the endomyocardial biopsy (EMB), an invasive and costly procedure. Purpose This study investigates the prognostic value of the pericoronary Fat Attenuation Index (FAI) and its role as a marker of inflammation and rejection in HT recipients. Methods A double-center observational retrospective study was conducted on a cohort of HT patients who underwent coronary computed tomography angiography (CCTA) between January 2016 and December 2022. FAI was measured with dedicated software and using the cut-off described in literature, we considered each coronary as "inflamed" if FAI was ≥ - 70,1 HU and "not inflamed" if FAI was < - 70,1 HU. Then, based on the number of inflamed coronary arteries for each patient, we divided the population into two comparison groups: high inflammatory (high INF) phenotype (alle three coronary arteries inflamed) and low inflammatory (low INF) phenotype (at least one coronary artery not inflamed). The primary endpoint was a composite of all-cause mortality, acute myocardial infarction, urgent revascularization and heart failure hospitalization. Furthermore, we investigated the correlation between FAI and cardiac rejection by looking for T cell-mediated rejection (TCMR) and antibody-mediated rejection (AMR) through EMB performed no more than six months before or after CCTA. Results A total of 101 HT patients were included; of this group 58 patients underwent EMBs within six months after or before the CCTA. The median duration of follow-up was 28 months. The composite endpoint occurred in 17 patients (16.8%). We documented 26 significative cardiac rejection episodes, 14 TCMR ≥ 2R and 12 AMR. The composite endpoint was achieved in 37.9% of patients with high INF phenotype compared to 8.3% with low INF phenotype (p < 0.001). In the multivariate analysis, the high INF phenotype remained an independent predictor of the composite endpoint in our population (HR: 10.5; 95% CI: 1.88-58.71; p = 0.007). Patients with TCMR and AMR had significantly higher FAI values. High INF phenotype correlated with the presence of ACR ≥ 2R (55.0% vs 7.9%, p < 0.001) and AMR (55.0% vs 2.6%, p < 0.001). Conclusion In HT patients, FAI is an independent predictor of major cardiovascular events. It is also associated with TCMR and AMR within six months from CCTA. FAI, therefore, may offer a non-invasive approach to stratify the prognosis of HT patients and serve as a valuable inflammatory biomarker for early diagnosis of cardiac rejection, supporting the use of CCTA in this setting of patients.Correlation FAI and MACECorrelation FAI and cardiac rejection

Incidence of acute cellular and antibody mediated rejection in heart transplantation from a tertiary care center

Abstract Background Heart transplant greatly increases the survival in patients with end stage heart failure. However, cardiologists and cardiothoracic surgeons face difficulty in detecting rejection at times. Post-cardiac transplant surveillance biopsy remains the gold standard for diagnosing rejection and therapeutic intervention. Purpose The objective is to report our experience of monitoring rejection by endomyocardial biopsy (EMB). Methods The index study is an ambispective one where we evaluated all the patients who underwent heart transplant at our center from 1994 to 2021. Results Heart transplant were carried out in 72 patients within a period of 28 years, with majority being done after 2016. The patients mean age was 31.6 years (10-59 years). The commonest indication was dilated cardiomyopathy (67%) followed by ischemic cardiomyopathy (2.5%), congenital heart disease (7%) and other miscellaneous causes (5%). The mean age of donors was 31.8 years (14-55 years). Eight of the 72 patients died without any post cardiac transplant endomyocardial biopsy. The remaining 64 patients underwent cumulatively a total of 271 endomyocardial biopsy procedures. Majority of endomyocaridal biopsies contained three cores (range 1-7). First EMB procedure was performed in 17 (26.6%) patients within first seven days, 35(53.1%) within the second week and 12(20.3%) after 14 days. Histologically rejection was identified in 42 (66%) patients. Thirty-nine (61%) had only acute cellular rejection (ACR), one (1.6%) had only antibody mediated rejection (AMR) and two (3.1%) had mixed ACR and AMR. These 42 patients with rejection had a total of 90 (33.2%) episodes of ACR detected in 271 endomyocardial biopsies. Out of 90 ACR, 44 (48.9%) occurred in less than six months; seventeen (18.9% of 90 ACR) episodes occurred between six and 12 months and 29 (32.2%) after one year. The mean of presentation of first ACR episode was 36 weeks (range 5 days to 3.6 years). There were 172 endomyocardial procedures within one year of transplantation of which 61 (35%) showed rejection. Ninety-nine endomyocardial procedures were performed one year of transplantation of which 29 (29%) showed rejection. Most common grade in both the time period was ACR grade 1R (International Society for Heart and Lung Transplantation (ISHLT) 2004) (72.1% in ≤1 year and 65.5% in >1 year) followed by 2R and 3R. Thirty-eight (90.4%) of 42 patients expired in less than five years since transplantation. Two (4.8%) patients survived between five to ten years post transplantation and two (4.8%) survived more than ten years. The longest cardiac transplant recipient had completed 23 years since cardiac transplant and is alive till date. Conclusions EMB being the gold standard for cardiac allograft rejection, the cardiac pathologists need to be aware of the various grades of rejection including mixed rejection.Acute cellular rejection (ISHLT 2004)

Successful eculizumab treatment as an adjunctive therapy to desensitization in ABO-incompatible living donor kidney transplantation and its molecular phenotypes

IntroductionABO-incompatible (ABOi) kidney transplantation (KT) has become an important option to overcome organ shortage. Plasmapheresis/rituximab-based desensitization therapy has successfully reduced anti-ABO antibody levels and suppressed antibody-mediated rejection (AMR) in ABOi KT. However, high titers of anti-ABO antibodies in some patients are refractory to standard desensitization, leading to loss of KT opportunities or AMR.MethodsEculizumab treatment was used an adjunctive therapy to rescue high-titer ABOi KT patients refractory to plasmapheresis/rituximab-based desensitization. Molecular phenotypes of allograft biopsies and cellular phenotypes of peripheral blood mononuclear cells of eculizumab group were compared with those of control groups using the Banff Human Organ Transplant gene panel and flow-cytometric analysis, respectively.ResultsThe initial titers of anti-ABO antibodies in the two patients were 1:512 and >1:1024; the final pre-transplant titers after desensitization were 1:128 and 1:64. Both patients received eculizumab from KT day to two or four weeks post-KT and maintained stable renal function up to one-year post-transplantation without overt infection, despite early episodes of probable AMR or borderline T cell-mediated rejection. Molecular phenotype analysis revealed that gene expression patterns in the ABOi KT with eculizumab group overlapped with those in the ABOi KT with AMR group more than in the ABOi KT without AMR group, except for complement pathway-related gene expression. Anti-ABO antibody titers decreased to low levels 1–3 months post-transplant in the eculizumab group in parallel with decreasing anti-B-specific B cells.ConclusionsShort-term eculizumab therapy is promising for rescuing ABOi KT recipients with high anti-ABO antibody titers refractory to plasmapheresis-based desensitization therapy.

Challenging endomyocardial biopsies' gold standard status in rejection screening: a prospective blinded study on cardiovascular magnetic resonance in heart transplant patients

Abstract Background The detection of rejection is crucial for graft survival after heart transplantation. Endomyocardial biopsies (EMBs) serve as the gold standard for rejection surveillance despite its limitations, while cardiac magnetic resonance (CMR), in conjunction with donor-derived cell-free DNA (dd-cfDNA) analysis, holds promise as a non-invasive approach. Purpose In this prospective blinded study, our aim was to evaluate feasibility of CMR for rejection screening, validating it against EMB, dd-cfDNA, and clinical status. Methods We blindly analyzed 250 studies involving CMR, EMB, dd-cfDNA, and clinical data in 58 heart transplant recipients (17 children and 41 adults). Of these 250 studies, 239 (96%) were assessed within 1 to 28 months after transplantation, and 11 studies (4%) 3-14 years post-transplant. In CMR T1- and T2-mapping analyses, acute rejection was defined by T1 or T2 times exceeding the specified thresholds (T1 ≥ 1060 ms, T2 ≥ 55 ms) in at least 2/16 heart segments. EMB findings were graded according to the ISHLT criteria (2005 and 2013), and acute cellular rejection (ACR) grade ≥ 2 or antibody-mediated rejection (AMR) grade ≥ 1 were considered significant. The cutoff for abnormal dd-cfDNA was set at 0.2%. Solely clinical rejection included patients with absent or normal EMB (ACR grade 0-1 and AMR grade 0), but with symptoms or ECG/echocardiographic findings indicative of acute rejection. Results Our study revealed 22 acute rejections, with 15 confirmed through EMB and 7 diagnosed solely based on clinical indicators. Among the EMB-confirmed cases, 3/15 exhibited AMR grade 1, 10/15 demonstrated ACR grade 2 and 2/15 ACR grade 3. CMR identified rejection in 77% (17/22) of cases. Specifically, it successfully identified rejection in 67% (10/15) of EMB-confirmed cases and 100% (7/7) of solely clinically diagnosed cases. Examining the concordance between CMR findings and dd-cfDNA levels, 35% (6/17) of the CMR-identified rejection cases exhibited abnormal dd-cfDNA, while 30% (5/17) showed normal levels. Notably, in one case, despite normal CMR results, both EMB and dd-cfDNA indicated rejection. Conversely, in four instances where EMB indicated acute rejection, both CMR and dd-cfDNA levels were normal. These findings highlight a potential discrepancy in the diagnostic accuracy of EMB, suggesting its tendency to both over- and underdiagnose acute heart transplant rejection. The integration of CMR and dd-cfDNA in the diagnostic process may provide a more comprehensive and reliable assessment of rejection episodes, offering valuable insights for clinical decision-making in heart transplant recipients. Conclusions EMB presents challenges in both under- and overdiagnosing rejection in heart transplant surveillance. A strategy based on CMR, combined with dd-cfDNA analyses, shows promise as a new gold standard for rejection screening.Flowchart

Donor-derived cell-free DNA versus left ventricular global longitudinal strain in noninvasive detection of heart allograft injury

Abstract Introduction Invasive endomyocardial biopsy (EMB) is still considered the gold standard method for monitoring heart transplant (HTx) rejection. However, it is associated with potentially serious complications, and its histopathologic interpretation has high interobserver variability. Thus, noninvasive methods for surveillance of the transplanted organ remains of great interest. The noninvasive donor-derived cell-free DNA is a marker of graft injury which can indicate acute rejection, even before the histopathological diagnosis of rejection detected by EMB. The assay has a high negative predictive value for acute rejection. Left ventricular global longitudinal strain (LV GLS) is an emerging marker of subclinical myocardial injury which plays a crucial role in the evaluation of several cardiac diseases; however, its role in HTx injury has so far been poorly investigated. Purpose We aimed to investigate the efficacy of a local laboratory-run dd-cfDNA assay-based heart transplant rejection surveillance programme, and the prognostic and discriminatory performance of LV GLS for subsequent heart allograft injury. Methods HTx recipients without a history of allograft rejection requiring intensification of immunosuppressive therapy were transitioned from our EMB-based surveillance protocol to dd-cfDNA-based rejection surveillance. We assessed the percentage of dd-cfDNA to total cell-free DNA. Injury cut-off was defined by a dd-cfDNA level ≥0.20%, while the severe injury threshold was at ≥0.35%. LV ejection fraction was calculated using 2D Simpson’s method. To derive LV GLS, we analyzed apical 4-chamber, 2-chamber, and long-axis images by 2D speckle tracking echocardiography. Results A total of 244 dd-cfDNA samples were analyzed from 46 patients in fifteen runs performed monthly between October 2022 and December 2023. The dd-cfDNA fraction remained below the injury cut-off in most patients (81%). There were no missed rejection episodes. 88% of routine EMBs that would have otherwise been performed were safely avoided. Eighteen for-cause EMBs were performed based on dd-cfDNA levels suggesting injury. One EMB verified moderate cellular rejection (ISHLT grade 2R) that required steroid pulse therapy. Two EMBs proved mild cellular rejection, one EMB confirmed mild antibody-mediated rejection, while one EMB proved mixed rejection. Thirteen EMBs found no rejection. Mean LVEF was preserved (57.6%±7.6%). Mean LV GLS was -15.1%±2.5% in the whole cohort, while -15.6%±4.7% in recipients with HTx rejection on indication EMB. There was no significant correlation between dd-cfDNA and LV GLS (n=159). Conclusion The noninvasive dd-cfDNA assay is effective in ruling out acute rejection and safely decreases the necessity of invasive surveillance EMBs after HTx. LV GLS is less sensitive in comparison with the dd-cfDNA assay for detection of myocardial injury in the early stages of graft rejection in HTx recipients at low risk for rejection.

Microvascular Inflammation of Kidney Allografts and Clinical Outcomes.

The heterogeneous clinical presentation of graft microvascular inflammation poses a major challenge to successful kidney transplantation. The effect of microvascular inflammation on allograft outcomes is unclear. We conducted a cohort study that included kidney-transplant recipients from more than 30 transplantation centers in Europe and North America who had undergone allograft biopsy between 2004 and 2023. We integrated clinical and pathological data to classify biopsy specimens according to the 2022 Banff Classification of Renal Allograft Pathology, which includes two new diagnostic categories: probable antibody-mediated rejection and microvascular inflammation without evidence of an antibody-mediated response. We then assessed the association between the newly recognized microvascular inflammation phenotypes and allograft survival and disease progression. A total of 16,293 kidney-transplant biopsy specimens from 6798 patients were assessed. We identified the newly recognized microvascular inflammation phenotypes in 788 specimens, of which 641 were previously categorized as specimens with no evidence of rejection. As compared with patients without rejection, the hazard ratio for graft loss was 2.1 (95% confidence interval [CI], 1.5 to 3.1) among patients with microvascular inflammation without evidence of an antibody-mediated response and 2.7 (95% CI, 2.2 to 3.3) among patients with antibody-mediated rejection. Patients with a diagnosis of probable antibody-mediated rejection had a higher risk of graft failure beyond year 5 after biopsy than those without rejection (hazard ratio, 1.7; 95% CI, 0.8 to 3.5). Patients with a diagnosis of either newly recognized microvascular inflammation phenotype had a higher risk of progression of transplant glomerulopathy during follow-up than patients without microvascular inflammation. Microvascular inflammation in kidney allografts includes distinct phenotypes, with various disease progression and allograft outcomes. Our findings support the clinical use of additional rejection phenotypes to standardize diagnostics for kidney allografts. (Funded by OrganX. ClinicalTrials.gov number, NCT06496269.).

Archetypal Analysis of Kidney Allograft Biopsies Using Next-generation Sequencing Technology.

In kidney transplantation, molecular diagnostics may be a valuable approach to improve the precision of the diagnosis. Using next-generation sequencing (NGS), we aimed to identify clinically relevant archetypes. We conducted an Illumina bulk RNA sequencing on 770 kidney biopsies (540 kidney recipients) collected between 2006 and 2021 from 11 European centers. Differentially expressed genes were determined for 11 Banff lesions. An ElasticNet model was used for feature selection, and 4 machine learning classifiers were trained to predict the probability of presence of the lesions. NGS-based classifiers were used in an unsupervised archetypal analysis to different archetypes. The association of the archetypes with allograft survival was assessed using the iBox risk prediction score. The ElasticNet feature selection reduced the number of the genes from a range of 859-10 830 to a range of 52-867 genes. NGS-based classifiers demonstrated robust performances (precision-recall area under the curves 0.708-0.980) in predicting the Banff lesions. Archetypal analysis revealed 8 distinct phenotypes, each characterized by distinct clinical, immunological, and histological features. Although the archetypes confirmed the well-defined Banff rejection phenotypes for T cell-mediated rejection and antibody-mediated rejection, equivocal histologic antibody-mediated rejection, and borderline diagnoses were reclassified into different archetypes based on their molecular signatures. The 8 NGS-based archetypes displayed distinct allograft survival profiles with incremental graft loss rates between archetypes, ranging from 90% to 56% rates 7 y after evaluation (P < 0.0001). Using molecular phenotyping, 8 archetypes were identified. These NGS-based archetypes might improve disease characterization, reclassify ambiguous Banff diagnoses, and enable patient-specific risk stratification.

Preoperative Factors Affecting Graft Survival After ABO-incompatible Adult Liver Transplantation.

Although ABO-incompatible liver transplantation (ABOi LT) has undergone remarkable progress, the prognostic factors are poorly understood. This study aimed to elucidate the preoperative factors affecting graft survival after ABOi LT. Patients who underwent ABOi LT between January 2012 and December 2020 at a single institution in South Korea were retrospectively reviewed. A total of 146 recipients, including 34 patients with graft loss, were analyzed. In the multivariate Cox proportional hazard model, recipient age (≥55 y; hazard ratio, 2.47; 95% confidence interval, 1.18-5.19; P = 0.017) and donor ABO type (donor A, hazard ratio, 3.12; 95% confidence interval, 1.33-7.33; P = 0.009) were significantly associated with an increased risk of graft loss. The most common cause of graft loss was recipient death due to bacterial infection (15/34, 44.1%). Both recipient age and donor ABO type were associated with an increased risk of recipient death due to bacterial infections. The incidence of complications after ABOi LT, including antibody-mediated rejection and diffuse intrahepatic biliary stricture, did not differ according to recipient age or donor ABO type. These findings suggest that recipient age and donor ABO type should be considered when preparing for ABOi LT. Careful monitoring and care after transplantation are required for recipients with preoperative risk factors.

Plasma exchange and intravenous immunoglobulin prolonged the survival of a porcine kidney xenograft in a sensitized, deceased human recipient.

The primary limitation to kidney transplantation is organ shortage. Recent progress in gene editing and immunosuppressive regimens has made xenotransplantation with porcine organs a possibility. However, evidence in pig-to-human xenotransplantation remains scarce, and antibody-mediated rejection (AMR) is a major obstacle to clinical applications of xenotransplantation. We conducted a kidney xenotransplantation in a deceased human recipient using a porcine kidney with five gene edits (5GE) on March 25th, 2024 at Xijing Hospital, China. Clinical-grade immunosuppressive regimens were employed, and the observation period lasted 22days. We collected and analyzed the xenograft function, ultrasound findings, sequential protocol biopsies, and immune surveillance of the recipient during the observation. The combination of 5GE in the porcine kidney and clinical-grade immunosuppressive regimens prevented hyperacute rejection. The xenograft kidney underwent delayed graft function in the first week, but urine output increased later and the single xenograft kidney maintained electrolyte and pH homeostasis from postoperative day (POD) 12 to 19. We observed AMR at 24h post-transplantation, due to the presence of pre-existing anti-porcine antibodies and cytotoxicity before transplantation; this AMR persisted throughout the observation period. Plasma exchange and intravenous immunoglobulin treatment mitigated the AMR. We observed activation of latent porcine cytomegalovirus toward the end of the study, which might have contributed to coagulation disorder in the recipient. 5GE and clinical-grade immunosuppressive regimens were sufficient to prevent hyperacute rejection during pig-to-human kidney xenotransplantation. Pre-existing anti-porcine antibodies predisposed the xenograft to AMR. Plasma exchange and intravenous immunoglobulin were safe and effective in the treatment of AMR after kidney xenotransplantation.

Pathologist Interrater Reliability and Clinical Implications of Elevated Donor-Derived Cell-Free DNA beyond Heart Transplant Rejection

BackgroundThere is significant variability amongst pathologists in the histopathological interpretation of the endomyocardial biopsy (EMB) for acute cellular rejection (ACR) and assessment of variability in the interpretation of antibody-mediated rejection (AMR) has not been reported. In contemporary practice, the strategy of allograft surveillance with donor-derived cell-free DNA (dd-cfDNA) as compared to EMB has not been compared with a focus on long-term clinical outcomes beyond acute rejection (AR). MethodsThe Genomic Research Alliance for Transplantation (GRAfT) is a multicenter, prospective cohort study that enrolled patients from 2015 to 2020. The center pathologist read was compared to two blinded core cardiac pathologists. ACR and AMR were graded based on the International Society for Heart and Lung Transplantation (ISHLT) criteria. Weighted Cohen’s kappa (κ) was used to evaluate interrater reliability between the center and core reads. To assess long-term outcomes, we evaluated a composite of AR, allograft dysfunction, and mortality within 1 year. ResultsThe study included 94 patients (median age 55 years [IQR 45, 62]), 30% female, 41% Black race) with a total of 429 EMBs and paired dd-cfDNA measures. The concordance rate between center and core pathologists was 77% for ACR (95%CI: 66% - 89%) and 63% for AMR (95%CI: 53% - 74%). 46 patients had an elevation in dd-cfDNA without AR by EMB. The median dd-cfDNA was 0.49% (IQR: 0.35, 1.01) and subsequent AR, allograft dysfunction, or mortality occurred in 59% of these patients at 1 year. In patients with AR by EMB and negative dd-cfDNA (n=5) the composite outcome occurred in 20% of patients at 1 year. At baseline, the positive likelihood ratio (LR+) of dd-cfDNA to detect AR by the center pathologist was 3.74 (95% CI 3.01 - 4.64) and core pathologist was 2.59 (95%CI: 1.95 - 3.45). If the composite outcome was included as a true positive, the LR+ of dd-cfDNA improved to 9.82 (95%CI: 7.04, 13.69) and7.63 (95% CI: 5.61, 10.38) at 1-year, respectively. ConclusionsPathologists interrater reliability is limited in both ACR and AMR. The positive LR of dd-cfDNA when compared to traditional histopathology is limited, but when longitudinal clinical outcomes are included to assess diagnostic performance, the LR+ improves significantly. The value of dd-cfDNA extends beyond the diagnosis of AR to include other clinically meaningful outcomes for patients after heart transplant.

NK Cells: Not Just Followers But Also Initiators of Chronic Vascular Rejection.

Chronic graft rejection represents a significant threat to long-term graft survival. Early diagnosis, understanding of the immunological mechanisms and appropriate therapeutic management are essential to improve graft survival and quality of life for transplant patients. Knowing which immune cells are responsible for chronic vascular rejection would allow us to provide effective and appropriate treatment for these patients. It is now widely accepted that natural killer (NK) cells play an important role in chronic vascular rejection. They can either initiate chronic vascular rejection by recognizing missing self on the graft or be recruited by donor-specific antibodies to destroy the graft during antibody-mediated rejection. Whatever the mechanisms of activation of NK cells, they need to be primed to become fully activated and damaging to the graft. A better understanding of the signaling pathways involved in NK cell priming and activation would pave the way for the development of new therapeutic strategies to cure chronic vascular rejection. This review examines the critical role of NK cells in the complex context of chronic vascular rejection.

Renal Allograft Macrophage Infiltration in Antibody-Mediated Renal Allograft Rejection

Abstract Introduction/Objective Macrophages are involved in the pathogenesis and contribute to acute and chronic renal allograft injury. We evaluated CD163+ (M2) macrophage graft tissue infiltration and its correlation with clinical and histological prognostic factors. Urinary soluble CD163, circulating total, and monocyte-derived microparticles (MMPs) in plasma were also estimated and correlated with tissue M2 macrophage infiltration. Methods/Case Report The study included forty-five renal allograft recipients with for-cause graft biopsy, with Antibody-mediated Rejection (ABMR) (n=30) or no evidence of rejection (NER) (n=15), from Jan 2021-Dec 2023, along with fifteen age-matched healthy controls (HC). On immunohistochemistry, CD163 positive cells were counted in glomeruli and tubulointerstitium. Urinary sCD163 was done by ELISA. Flow cytometry quantified plasma MPs (AnnexinV+) and MMPs (CD14+/ AnnexinV+). Results (if a Case Study enter NA) The mean age of renal allograft recipients was 35±9yrs (all males). Mean s.creatinine in ABMR and NER was 3±2.6 and 2±0.5 mg/dl, respectively. ABMR had significantly more glomerular (16.2±13.7/10 glomeruli) and tubulointerstitial (183±108/10hpf) M2 macrophage (CD163+) cell infiltration than NER (4.8±4.7/10 glomeruli; 133.5±108/10hpf). Urinary sCD163 in ABMR was also significantly raised (0.89±0.63ng/ml) than in NER. It was not detectable in HC. Plasma MMPs were elevated in ABMR [25% of total MPs (1.62x104)] as compared to NER [8.2 % of total MPs (1.4x104)] and HC [7.8% of total MPs (1.2x104)]. In ABMR, the glomerular CD163+ cells correlated with urinary sCD163 levels (r=0.350, p=0.050) and circulating MMPs (r=0.526, p=0.002). Conclusion We found that in renal allograft recipients with ABMR, there is significantly higher graft biopsy glomerular CD163+ (M2) macrophage infiltration and elevated urinary sCD163 levels as compared to NER. The plasma circulating MMPs were also elevated in ABMR. Our findings suggest that monocyte activation plays a significant role in the pathogenesis and injury in ABMR. Non-invasive markers of monocyte activation can distinguish ABMR from NER in allograft recipients presenting with allograft dysfunction.

C1q Binding Ability for Prior Risk Assessment of Acute Antibody-Mediated Rejection in ABO-Incompatible Kidney Transplantation.

In ABO blood group incompatible kidney transplantation (ABO-I), potential issues on acute antibody-mediated rejection (ABMR) remain to be solved. This study aimed to assess the risk factors of acute ABMR using recipient- or donor-derived specimens. Quantitative analysis of A/B antigen expression was conducted in 104 donor kidney tissues (Kt), platelets (Plt), and red blood cells (RBC) by immunohistochemical staining or flow cytometry (FCM). ABO-I pre-transplant recipient serum samples (ABMR = 12, non-ABMR = 27) were extracted by propensity score matching. Anti-A antibody titers of IgM, IgG and IgG subclasses, and C1q binding ability (%) on antibody were measured using RBC-FCM. No association was observed between ABMR and A/B antigen expression levels in donor's Plt, RBC, or Kt. In recipient's sample, C1q-IgG binding ability was significantly higher in the ABMR group than in the non-ABMR group (C1q-IgG: 9.04% vs. 5.93% p = 0.049). Neither the A/B antigen expression level in donors (grafts) nor anti-blood group IgG/IgM antibodies in recipient sera before desensitization seemed to influence ABMR incidence in ABO-I. In contrast, C1q-IgG binding ability could be a potential predictor for ABMR in ABO-I.

Risk of cellular or antibody-mediated rejection in pediatric kidney transplant recipients with BK polyomavirus replication-an international CERTAIN registry study.

In kidney transplant recipients (KTR), BK polyomavirus-associated nephropathy (BKPyVAN) is a major cause of graft loss. To facilitate the clearance of BKPyV-DNAemia, reduction of immunosuppression is currently the treatment of choice but may increase the risk of graft rejection. This international CERTAIN study was designed to determine the risk of alloimmune response and graft dysfunction associated with immunosuppression reduction for BKPyV treatment in 195 pediatric KTR. BKPyV-DNAemia was associated with a more than twofold increased risk of late T cell-mediated rejection (TCMR) (HR 2.22, p = 0.024), of de novo donor-specific HLA antibodies (dnDSA) and/or antibody-mediated rejection (ABMR) (HR 2.64, p = 0.002), and of graft function deterioration (HR 2.73, p = 0.001). Additional independent risk factors for dnDSA/ABMR development were a higher HLA mismatch (HR 2.72, p = 0.006) and re-transplantation (HR 6.40, p = 0.000). Other independent predictors of graft function deterioration were TCMR (HR 3.98, p = 0.003), higher donor age (HR 1.03, p = 0.020), and re-transplantation (HR 3.56, p = 0.013). These data indicate that reduction of immunosuppression for BKPyV-DNAemia management is associated with increased alloimmune response in pediatric KTR. Therefore, regular dnDSA screening and close monitoring of graft function in case of BKPyV-DNAemia followed by subsequent reduction of immunosuppressive therapy are recommended.

Circulating Immune Complexes and Complement Activation in Sensitized Kidney Transplant Recipients.

Chronic antibody-mediated rejection in kidney transplantation is a common cause of graft loss in the late post-transplant period. In this process, the role of the classical complement activation pathway is crucial due to the formation of immune complexes between donor-specific antibodies (DSAs) and donor antigens and the attachment of the C1q complement fragment. This study aimed to determine the levels of circulating C1q immunocomplexes (CIC-C1q) and complement activation (CH50), in sensitized kidney transplant recipients (KTRs). In this cross-sectional study we used serum samples from KTRs with de novo or preformed DSAs (n = 14), KTRs without DSAs (n = 28), and 22 subjects with no history of chronic kidney disease (controls). C1q immunocomplexes and CH50 concentration in serum were measured with the enzyme immunoassay (EIA) kit MicroVue CIC-C1q (Quidel, Athens, OH, USA) and EIA kit MicroVue CH50 (Quidel, OH, USA), respectively. Higher concentrations of CIC-C1q was observed in KTRs with DSAs in comparison with controls and with KTRs with no DSAs (6.8 ± 2.7 and 4.8 ± 1.9 vs. 5.0 ± 1.2 μg Eq/mL, respectively, p < 0.01). We found no difference in CIC-C1q between KTRs with no DSAs and controls. CIC-C1q levels were positively correlated with DSA titer. CH50 levels were decreased in KTRs with DSAs in comparison with controls and KTRs with no DSAs (39 ± 15 vs. 68 ± 40 and 71 ± 34 U Eq/mL, respectively, p < 0.01). There was no difference in CH50 between DSA-negative KTRs and controls. Kidney transplant recipients with DSAs had increased serum levels of C1q immunocomplexes and increased classical pathway complement activation.

Histopathological Characteristics of Percutaneous Endomyocardial Biopsy in Heart Transplant Rejection Surveillance: A Single Center Experience.

Heart transplantation (HT) remains the ultimate treatment for end-stage heart failure. An endomyocardial biopsy (EMB) is "the gold standard" diagnostic procedure used in HT rejection surveillance. The aim of this study is to provide a detailed analysis of the histopathological characteristics of the EMB and to investigate if there is a correlation between some histopathological changes, such as fibrosis, vasculitis, Quilty effect (Q.E.), myocytes damage, and the presence of episodes of acute rejection. In this retrospective study, 200 EMBs were included, coming from 65 patients transplanted in the Emergency Institute for Cardiovascular Diseases and Transplantation (ICvDT) Targu Mures between 2012 and 2024. Fibrosis, vasculitis, Q.E., myocyte damage, etc., were microscopically evaluated to see if these parameters correlate with rejection episodes. The mean age was 38.18 years (SD 15.67), 25% of biopsies being recorded in the 41-50 age group. 77.14% of total acute cellular rejection (ACR) was of mild rejection, with most registered in the 11-20 age group; the cases of severe rejection being recorded in the 41-50 age group. Antibody-mediated rejection (AMR) was recorded more frequently in women with a representation of 23.4%, compared to 8.5% of men. 86.7% (39 cases) of the total number of EMBs with fibrosis score 3 and 71.4% (15 cases) of the total EMBs with fibrosis score 2 were recorded in men, compared to the 28.6% (6 cases) of fibrosis score 2 recorded in women (p = 0.013). 50.0% of all the EMB recorded in the 61-70 age group showed fibrosis score 3, compared to 34.8% of those from the 21-30 age group. The Q.E. was identified in 13% of the biopsies and, in some patients, it was observed across 3-4 successive biopsies. Mild vasculitis was associated in 34.9% of cases with ISHLT ≥ 1R and moderate vasculitis was associated in 87.5% of cases with ISHLT ≥ 1R. Fibrosis was detected much more frequently in men and in the 61-70 age group. In addition to the histopathological changes specific to acute rejection, there are other pathological changes, such as the Q.E., and vasculitis and myocytes damage and disarray, that seem to suggest a close connection with rejection, but extensive studies are needed to confirm this.