Humoral Rejection Research Articles

Molecular monitoring of lung allograft health: is it ready for routine clinical use?

Maintenance of long-term lung allograft health in lung transplant recipients (LTRs) requires a fine balancing act between providing sufficient immunosuppression to reduce the risk of rejection whilst at the same time not over-immunosuppressing individuals and exposing them to the myriad of immunosuppressant drug side-effects that can cause morbidity and mortality. At present, lung transplant physicians only have limited and rather blunt tools available to assist them with this task. Although therapeutic drug monitoring provides clinically useful information about single time point and longitudinal exposure of LTRs to immunosuppressants, it lacks precision in determining the functional level of immunosuppression that an individual is experiencing. There is a significant gap in our ability to monitor lung allograft health and therefore tailor optimal personalised immunosuppression regimens. Molecular diagnostics performed on blood, bronchoalveolar lavage or lung tissue that can detect early signs of subclinical allograft injury, differentiate rejection from infection or distinguish cellular from humoral rejection could offer clinicians powerful tools in protecting lung allograft health. In this review, we look at the current evidence behind molecular monitoring in lung transplantation and ask if it is ready for routine clinical use. Although donor-derived cell-free DNA and tissue transcriptomics appear to be the techniques with the most immediate clinical potential, more robust data are required on their performance and additional clinical value beyond standard of care.

HLA Typing and Donor-Specific Antibody Screening in Kidney Transplantation: Bridging the Past to the Future

Human leukocyte antigens (HLA) are unique proteins expressed on the surface of human cells, playing a pivotal role in the immune system, particularly in the contexts of infection, cancer, and transplantation. The widespread adoption of HLA typing methods has become an essential component in assessing donor-recipient compatibility, a crucial limiting factor in solid organ transplantation. In general, the greater the disparity between a donor's and recipient's HLA types, the higher the likelihood of provoking an alloimmune response, which frequently results in alloimmune graft rejection. With significant advancements in organ transplantation techniques, immunosuppressive medications, and surgical procedures, attention has increasingly turned toward understanding and managing humoral rejection processes. Pre-transplant antibody screening plays a critical role in identifying individuals with elevated levels of antibodies against potential donor antigens. This screening aids in risk assessment and planning to mitigate the risk of antibody-mediated rejection (AbMR). Several methods are available for assessing circulating antigen-specific antibodies and HLA tissue typing, including cell-based assays like serological assays, complement-dependent cytotoxicity, and flow cytometry. However, non-cell-based approaches, such as molecular methods, HLA imputation techniques and high-throughput HLA-matchmaker assays have gained significant popularity due to their ability to provide higher resolution and robust donor-recipient matching. Despite the advancements in precision and sensitivity observed in HLA cutting-edge technologies, numerous challenges still persist. These challenges involve complexities linked to allelic ambiguities, the differentiation of closely related alleles, and the ongoing effort to establish a standardized HLA testing methodology across diverse laboratories. Additionally, correlating the HLA crossmatch results with the clinical outcomes for transplant donors poses another important aspect that warrants attention and requires expert analysis. In this review, we will enumerate the different methods of HLA typing and DSA screening and discuss the unmet needs and future directions for HLA typing methods.

De Novo Membranous Nephropathy and Humoral Rejection: A Different Presentation with a Shared Alloimmune Trigger

De Novo Membranous Nephropathy and Humoral Rejection: A Different Presentation with a Shared Alloimmune Trigger

Everolimus plus reduced calcineurin inhibitor prevents de novo anti-HLA antibodies and humoral rejection in kidney transplant recipients: 12-month results from the ATHENA study.

Studies prospectively monitoring de novo donor-specific antibodies (dnDSAs) and their clinical impact are sparse. This substudy of ATHENA was initiated to evaluate the effect of everolimus (EVR) or mycophenolic acid (MPA) in combination with reduced calcineurin inhibitor (CNI, tacrolimus [TAC] or cyclosporine [CsA]) on the formation of human leukocyte antibodies (HLA), including dnDSA, and the impact on clinical outcomes in kidney transplant (KTx) recipients. All eligible patients were randomized 1:1:1 to receive either EVR + TAC, EVR + CsA or MPA + TAC, with basiliximab induction plus steroids after transplantation up to Month 12. The incidence of dnDSA by treatment group and the association with clinical events were evaluated descriptively as an exploratory objective in the intent-to-treat (ITT) and per-protocol (PP) populations with at least one antibody assessment. Overall, none of the patients in the EVR + TAC group had either dnDSA or antibody mediated rejection (PP or ITT population) and only one patient with dnDSA in the TAC + MPA group had antibody mediated rejection. The EVR regimen was comparable to MPA regimen with an extremely low incidence of dnDSA over 1 year of treatment.

In vitro and in vivo immune assessments of genetically-engineered pig skin grafts in New World (squirrel) monkeys.

Half a million patients in the USA alone require treatment for burns annually. Following an extensive burn, it may not be possible to provide sufficient autografts in a single setting. Genetic manipulations (GM) of pigs offer the possibility of reducing primate humoral and cellular rejection of pig skin xenografts and thus extending graft survival. We compared the survival of skin grafts from pigs with 9-GM with that of autografts and allografts in squirrel monkeys. Monitoring for rejection was by (1) macroscopic examination, (2) histopathological examination of skin biopsies, and (3) measurement of anti-monkey and anti-pig IgM and IgG antibodies. Autografts (n = 5) survived throughout the 28 days of follow-up without histopathological features of rejection. Median survival of allografts (n = 6) was 14 days and of pig xenografts (n = 12) 21 days. Allotransplantation was associated with an increase in anti-monkey IgM, but the anticipated subsequent rise in IgG had not yet occurred at the time of euthanasia. Pig grafts were associated with increases in anti-pig IgM and IgG. In all cases, histopathologic features of rejection were similar. 9-GM pig skin xenografts survive at least as long as monkey skin allografts (and trended to survive longer), suggesting that they are a realistic clinical option for the temporary treatment of burns. Although monkeys with pig skin grafts developed anti-pig IgM and IgG antibodies, these did not cross-react with monkey antigens, indicating that a primary 9-GM pig skin graft would not be detrimental to a subsequent monkey skin allograft.

Pregnancy in a heart transplant recipient with history of severe humoral and cellular rejection and positive donor-specific antibodies – case report

Pregnancy in a heart transplant recipient with history of severe humoral and cellular rejection and positive donor-specific antibodies – case report

Belatacept inhibit human B cell germinal center development in immunodeficient mice

The humoral response mediated by alloantibodies directed against donor HLA molecules (DSAs) is one of the main causes of graft loss in kidney transplantation. Understanding the pathophysiology leading to humoral kidney rejection as the development of therapeutic tools is therefore a main objective in the field of solid organ transplantation and necessitate adapted experimental models. Among the immunosuppressive agents used in renal transplantation, belatacept, a fusion protein targeting T costimulatory molecules has shown its ability to prevent more efficiently the secretion of DSA by different mechanisms including a direct action on plasma cells but also on B lymphocytes and follicular helper T lymphocytes (Tfh) cooperation. This cellular cooperation occurs within germinal centers (GC), the seat of B lymphocytes differentiation. Here, we aimed to develop a dedicated mouse model in which human GC would be functional to study the effect of belatacept on GC formation and the ability of B lymphocytes to secrete immunoglobulin. We next demonstrate that belatacept inhibits the formation of these GCs, by inhibiting the frequency of Tfh and B lymphocytes. This alters the B maturation and therefore the generation of plasma cells and consequently, immunoglobulin secretion.

The Enigma of Heart-kidney Transplantation.

The Enigma of Heart-kidney Transplantation.

#6369 RESULTS OF KIDNEY TRANSPLANTATION IN PATIENTS WITH LOW MFI PREFORMED DONOR SPECIFIC ANTIBODIES

Abstract Background and Aims Preformed DSA at transplantation, significantly increase risk of antibody-mediated rejection (ABMR). While pre-existing positive DSA with concomitant positive cross-match is a general contra-indication to kidney transplantation, DSA presence with negative crossmatch is still a controversial topic. The presence of DSA with Mean Fluorescence Index (MFI) up to 3.000 and a negative cross-match is not valued as a contraindication to transplantation and is widely accepted. In some transplant centers the chance of transplantation is also offered to DSA positive patients, with MFI up to 5.000. Aim of this study was to analyze graft and patient survival, acute cellular rejection, humoral rejection, renal function and side effects in kidney transplant recipients (KTR) with positive DSA (MFI up to 3.000) and negative cross-match. Method Nineteen pts (age 53+/-11) with chronic renal failure on chronic hemodialysis treatment (8+/-6 years) received a kidney transplant between May 2017 and December 2020. Median PRA was 66%; 100% pts had DSA with average MFI 2122 (min 1039, max 3779). As immunosuppressive therapies all pts received induction with Thymoglobuline plus Rituximab, followed by maintenance immunosuppression with Tacrolimus, MofetilMycoFenolate and Steroids. All patients were on periodic follow up in our Transplant Clinic. Mean follow up was 26.5+/-14.4 months. Results were compared to a concomitant KTR group DSA and crossmatch negative. Results After 2y follow-up, 17/19 pts are alive (89.5%), one patient died (1/19, 5.2%) after treatment for ABMR. Three patients returned to dialysis treatment (15.8%) during the first year post-tx, because of: PNF 1pt; irreversible ABMR rejection 2 pts. One other patient had reversible ABMR. Cumulative one year graft survival was 79% and the cumulative incidence of ABMR was 15.8%. Average 2 years follow-up creatinine was 1.46+/-0.88 mg/dl, median 2 year GFR was 51+/-25 ml/min. Comparing the matched control group (19 pts DSA and cross-match negative) 2 years patient survival, graft survival, GFR, acute rejection were not significantly different. Incidence of acute rejection was higher in the DSA positive group (16% vs 0%), as well as graft loss (21% vs 12%). Conclusion Our data suggest that low dose Thymoglobuline plus Rituximab induction allow kidney transplantation in recipient with high PRA (69%) and positive DSA with low MFI (< 3.000), with higher risk of acute rejection, and graft loss.

#2649 INFECTIOUS COMPLICATIONS AFTER KIDNEY TRANSPLANTATION IN RELATION TO INDUCTION IMMUNOSUPPRESSIVE THERAPY

Abstract Background and Aims Infections are the most common non-cardiac cause of death after kidney transplantation (KT). The main goal of immunosuppressive therapy is to find a balance between the low incidence of acute rejection and infectious complications. Method We conducted a retrospective, monocentric analysis of transplant patients at the Transplant Center University Hospital Martin from 2011 to 2020 with various induction immunosuppressive therapies. We monitored the incidence of infections in terms of etiology, localization and severity at different intervals after KT. Results Our study included 39 patients on induction therapy with basiliximab to whom we paired 39 patients with induction therapy with thymoglobulin based on gender and age, in total our population consisted of 78 patients (56 men, 22 women), the mean age was 45 years. In the group of patients with induction therapy with thymoglobulin, we noted a higher proportion of fungal (P=0.0409), urogenital infections (P=0.0384), sepsis (P=0.0497) and leukopenia (0.0384) from 1st to 6th month after KTx, higher incidence of skin infections (P= 0.0218) and serious infections requiring hospitalization (P = 0.0269) from 6th-12th months to TO. On the other hand, in the basiliximab patient group, we identified a higher incidence of acute humoral and cellular rejection (P=0.0218) after 6 months of TO. From the perspective of recurrent infections, in the Thymoglobulin induction group, we noted a higher incidence of infections by localization, etiology and severity. Risk factors for recurrent bacterial infections from 1st to 6th month after KT are: history of respiratory diseases (P = 0.0108), thrombocytopenia (P = 0.0104) and infections caused by multi-resistant bacteria (P = 0.0003). Conclusion Patients on inductive immunosuppressive therapy with thymoglobulin are at a higher risk of recurrent, multidrug-resistant and severe infections after KT compared to induction with basiliximab with identical maintenance immunosuppressive therapy. On the other hand, patients on induction therapy with basiliximab have a higher risk of developing acute rejection. Therefore, it is essential to identify risk groups of patients benefiting from milder or more intensive inductive immunosuppressive therapy without a concomitant increased risk of infectious complications or acute graft rejection

#4856 HISTOLOGICAL FINDINGS OF ACUTE HUMORAL REJECTION IN PATIENTS WITH STANDARD IMMUNOLOGICAL RISK: ANTIBODY-MEDIATED DAMAGE OR MICROVASCULAR INJURY?

Abstract Background and Aims The development of acute humoral rejection (AHR) is increased in patients with high immunological risk. Taking into account the highly sensitivity from the techniques used to determine anti-HLA antibodies, the histological findings of AHR in the immediate post-transplantation period in patients without preformed anti-HLA antibodies (standard immunological risk) is unexpected. We propose the implication of non-immunological factors as the origin of these findings. Our aim was to evaluate the histological findings of AHR in the immediate post-transplantation period in patients with standard immunological risk and to analyze factors related to its appearance. Method A multicenter retrospective study was carried out including renal transplants performed between January-2014 and december-2022, excluding patients with pre-transplant HLA sensitization and failures due to thrombosis. A descriptive analysis of transplant recipients with standard immunological risk who developed histological findings of AHR was made (AHRh) .In addition, we performed a comparative analysis of this group with the patients who developed AHR with pre-transplant HLA sensitization (AHRs). Results Of the 351 patients, 18 (5.1%) presented AHRh, all were first transplants without pre-transplant anti-HLA antibodies. Fourteen donors were brain death and four due to controlled circulatory arrest. Banff AHR was grade I in 1 patient, grade II in 13 patients, and III in 3 cases. 50% showed thrombotic microangiopathy (TMA). Seven (38.9%) failed after a mean follow-up of 28.7±26.1 months. The failure etiologies were chronic rejection (3) and primary dysfunction (4). No patient presented anti-HLA antibodies during the follow-up and 3 have received a second transplant without complications. When comparing the AHRh group with the AHRs (n = 14), we observed a greater age of the donor in AHRh (median 71,5 vs 56.5, p = 0.02) a higher percentage of donor due to controlled circulatory arrest (22% vs 0%, p = 0.075) and with history of Hypertension (66.7% vs 42.9%, p = 0.09). Recipient age was higher in AHRh (median 64.5 vs 51, p = 0.025), with a higher proportion of retransplant in AHRs (42.9% vs 0, p = 0.002). In AHRh, DGF (100% vs 57.1%, p = 0.002) and thrombotic microangiopathy (50% vs 14.3%, p = 0.03) were more frequent. Renal function was worse during the follow-up in AHRh (p<0.05). No differences have been observed in graft and patient survival. Conclusion The histological finding of RAH in patients with standard immunological risk appears as an aggressive process with negative consequences on graft survival. The absence of anti-HLA antibodies in subsequent follow-up suggests the involvement of non-immunological factors in its developing. Processes related to the maintenance and/or extraction of organs could favor the appearance of microvascular damage, with histological findings suggestive of AHR especially in older grafts and with comorbidity. Studying these cases is essential to identify risk groups and establish appropriate therapeutic strategies.

Mechanism and treatment for chronic antibody-mediated rejection in kidney transplant recipients.

Chronic antibody-mediated rejection of kidney transplantation is a major cause of late-stage graft loss. Donor-specific antibodies are the main cause of antibody-mediated rejection; in particular, de novo donor-specific antibodies are a risk factor for chronic active antibody-mediated rejection. The level of de novo donor-specific antibodies tends to increase with time throughout long-term graft survival. Donor-specific antibodies induce humoral rejection through complement activation, which results in tissue injury and coagulation. Additionally, complement activation promotes the migration of inflammatory cells through the innate immune response, causing endothelial injury. This inflammatory response may cause persistent glomerulitis and peritubular capillaritis, leading to fixed pathological lesions that impair graft function. No treatment has been established for chronic antibody-mediated rejection, a condition in which antibody-mediated rejection becomes irreversible. Thus, antibody-mediated rejection must be detected and treated while it is still reversible. In this review, we discuss the development of de novo donor-specific antibodies and the mechanisms leading to chronic antibody-mediated rejection and summarize the current treatment options and the latest biomarkers for detecting chronic antibody-mediated rejection at an earlier stage.

Efficacy of Double Membrane Filtration Immunoadsorption in Severe C1q-Binding Donor-Specific Antibody-Positive Acute Humoral Kidney Allograft Rejection: A Case Series

Introduction: Acute antibody-mediated rejection (ABMR) is an important threat to renal allograft survival in the early transplant period and the major single cause of graft loss in the first postoperative year. Semi-selective immunoadsorption (IA) remains one of the commonly applied treatments in ABMR, reducing allo-reactive antibody load. Adding double filtration plasmapheresis (DFPP) to IA might enhance therapeutic efficacy by also addressing innate humoral effectors like complement factors. Methods: Four patients with ABMR were treated with DFPP + IA. Clinical, histological, and immunological data and adverse events were retrospectively collected. Results: Here we present four high-risk treatment-refractory ABMR cases with C1q-binding donor-specific antibodies and histology of humoral rejection under treatment with DFPP + IA. While the earlier cases (within the first year after transplantation) showed marked reduction in ABMR severity and improvement of kidney function, the later cases did not respond accordingly. Late ABMR patient 1 stabilized, whereas late ABMR patient 2 did not respond to treatment. Conclusions: Our data support the consideration of DFPP + IA as a rescue treatment option in early, severe, high-risk ABMR cases in which other treatments failed.

MP31-08 KIDNEY TRANSPLANTATION FROM DONATION AFTER BRAIN DEATH VERSUS DONATION AFTER CIRCULATORY DEATH USING ABDOMINAL NORMOTHERMIC OXYGENATED CIRCULATION IS THERE A DIFFERENCE IN SURGICAL COMPLICATIONS?

You have accessJournal of UrologyCME1 Apr 2023MP31-08 KIDNEY TRANSPLANTATION FROM DONATION AFTER BRAIN DEATH VERSUS DONATION AFTER CIRCULATORY DEATH USING ABDOMINAL NORMOTHERMIC OXYGENATED CIRCULATION IS THERE A DIFFERENCE IN SURGICAL COMPLICATIONS? Alberto Costa Silva, Teresa Pina-Vaz, Margarida Manso, Tiago Antunes-Lopes, Afonso Morgado, Carlos Martins-Silva, and João Alturas-Silva Alberto Costa SilvaAlberto Costa Silva More articles by this author , Teresa Pina-VazTeresa Pina-Vaz More articles by this author , Margarida MansoMargarida Manso More articles by this author , Tiago Antunes-LopesTiago Antunes-Lopes More articles by this author , Afonso MorgadoAfonso Morgado More articles by this author , Carlos Martins-SilvaCarlos Martins-Silva More articles by this author , and João Alturas-SilvaJoão Alturas-Silva More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003264.08AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Donation after circulatory death (DCD) is being considered a reliable source of kidneys given the scarcity of donation after brain death with standard- (DBD/SCD) and expanded-criteria (DBD/ECD). Our center has started a transplantation program for uncontrolled DCD donors after unsuccessful resuscitation (Maastricht II donors) using extracorporeal normothermic membrane oxygenation (ECMO). Our objective was to compare the surgical complications of kidney transplants from DCD/ECMO versus donation after DBD with SCD and ECD. METHODS: From January 2016 to October 2021, a prospective study was performed and three groups were considered – DCD/ECMO, DBD/SCD and DBD/ECD. Demographic data from donors and recipients were collected. Graft function evolution was assessed using creatine and glomerular filtration rate. Delayed graft function (DGF) was defined as the need for dialysis in the first week after transplantation. Surgical complications were classified as arterial, venous, ureteral, lymphatic, suture dehiscence, and/or need for early graft removal (defined as removal in the first 3 months after transplantation). The cause of early graft removal was noted and categorized as either a surgical or non-surgical complication. RESULTS: A total of 100 kidneys were implanted from DCD/ECMO, 108 from DBD/SCD and 115 from DBD/ECD.Despite a higher rate of DGF in DCD/ECMO groups vs DBD/SCD and DBD/EDC (65,9% vs 28,1% vs 30,8%; p<0,001), there were no differences in renal function between groups 12 months after transplantation. There were no statistically significant differences in surgical complications. Early graft removal was lower in DBD-SCD group. DCD/ECMO group had a significantly more early graft removals of non-surgical cause due to tubular necrosis, humoral rejection or infection, while DBD/ECD had a significantly more early graft removals of surgical cause due to arterial/venous thrombosis and hemorrhage. CONCLUSIONS: Kidney transplantation from DCD/ECMO can be a viable option. Despite higher rates of DGF in DCD/ECMO, those whose grafts survive have a similar renal function in the medium-to-long term. Early graft removal was mainly associated with a non-surgical cause, probably related to ischemia lesion caused by prolonged warm ischemia time and/or ischemia-reperfusion injury induced by the ECMO. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e432 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Alberto Costa Silva More articles by this author Teresa Pina-Vaz More articles by this author Margarida Manso More articles by this author Tiago Antunes-Lopes More articles by this author Afonso Morgado More articles by this author Carlos Martins-Silva More articles by this author João Alturas-Silva More articles by this author Expand All Advertisement PDF downloadLoading ...

Adiponectin/leptin ratio as a predictor of acute rejection in early post-transplant period in patients after kidney transplantation.

Adipokines are largely involved in the regulation of immune system activity. While leptin is the main pro-inflammatory marker of adipose tissue, adiponectin is characterized by anti-inflammatory effects. The aim of our study was to determine the risk of acute graft rejection in protocol biopsy depending on the adiponectin/leptin (A/L) ratio in patients after kidney transplantation (KT). A total of 104 patients were included in the prospective analysis, in whom the levels of adipokines were examined pre-transplant, in the 3rd month after KT and the A/L ratio was calculated. In the 3rd month after KT, all patients underwent protocol biopsy of the graft and examination of donor-specific antibodies (DSA) using the Luminex method. After adjusting for differences in the basic characteristics of the donor and recipient, we identified a subgroup with A/L ratio < 0.5 pre-transplant [HR 1.6126, (P = 0.0133)] and 3 months after KT [HR 1.3150, (P = 0.0172)] as independent risk factor for acute graft rejection. In the subsequent specification of the rejection episode, we identified the risk ratio A/L < 0.5 before KT [HR 2.2353, (P = 0.0357)] and 3 months after KT [HR 3.0954, (P = 0.0237)] as independent risk factor for the development of acute humoral rejection with DSA positivity. This is the first study to investigate the relationship between A/L ratio and immunological risk in terms of the development of rejection changes in patients after KT. In our study, we found that A/L ratio < 0.5 is an independent risk factor for the development of acute humoral rejection and de novo DSA production in the third month after KT.

Validation of automatically measured T1 map cortico-medullary difference (ΔT1) for eGFR and fibrosis assessment in allograft kidneys.

MRI T1-mapping is an important non-invasive tool for renal diagnosis. Previous work shows that ΔT1 (cortex-medullary difference in T1) has significant correlation with interstitial fibrosis in chronic kidney disease (CKD) allograft patients. However, measuring cortico-medullary values by manually drawing ROIs over cortex and medulla (a gold standard method) is challenging, time-consuming, subjective and requires human training. Moreover, such subjective ROI placement may also affect the work reproducibility. This work proposes a deep learning-based 2D U-Net (RCM U-Net) to auto-segment the renal cortex and medulla of CKD allograft kidney T1 maps. Furthermore, this study presents a correlation of automatically measured ΔT1 values with eGFR and percentage fibrosis in allograft kidneys. Also, the RCM U-Net correlation results are compared with the manual ROI correlation analysis. The RCM U-Net has been trained and validated on T1 maps from 40 patients (n = 2400 augmented images) and tested on 10 patients (n = 600 augmented images). The RCM U-Net segmentation results are compared with the standard VGG16, VGG19, ResNet34 and ResNet50 networks with U-Net as backbone. For clinical validation of the RCM U-Net segmentation, another set of 114 allograft kidneys patient's cortex and medulla were automatically segmented to measure the ΔT1 values and correlated with eGFR and fibrosis. Overall, the RCM U-Net showed 50% less Mean Absolute Error (MAE), 16% better Dice Coefficient (DC) score and 12% improved results in terms of Sensitivity (SE) over conventional CNNs (i.e. VGG16, VGG19, ResNet34 and ResNet50) while the Specificity (SP) and Accuracy (ACC) did not show significant improvement (i.e. 0.5% improvement) for both cortex and medulla segmentation. For eGFR and fibrosis assessment, the proposed RCM U-Net correlation coefficient (r) and R-square (R2) was better correlated (r = -0.2, R2 = 0.041 with p = 0.039) to eGFR than manual ROI values (r = -0.19, R2 = 0.037 with p = 0.051). Similarly, the proposed RCM U-Net had noticeably better r and R2 values (r = 0.25, R2 = 0.065 with p = 0.007) for the correlation with the renal percentage fibrosis than the Manual ROI results (r = 0.3, R2 = 0.091 and p = 0.0013). Using a linear mixed model, T1 was significantly higher in the medulla than in the cortex (p<0.0001) and significantly lower in patients with cellular rejection when compared to both patients without rejection and those with humoral rejection (p<0.001). There was no significant difference in T1 between patients with and without humoral rejection (p = 0.43), nor between the types of T1 measurements (Gold standard manual versus automated RCM U-Net) (p = 0.7). The cortico-medullary area ratio measured by the RCM U-Net was significantly increased in case of cellular rejection by comparison to humoral rejection (1.6 +/- 0.39 versus 0.99 +/- 0.32, p = 0.019). In conclusion, the proposed RCM U-Net provides more robust auto-segmented cortex and medulla than the other standard CNNs allowing a good correlation of ΔT1 with eGFR and fibrosis as reported in literature as well as the differentiation of cellular and humoral transplant rejection. Therefore, the proposed approach is a promising alternative to the gold standard manual ROI method to measure T1 values without user interaction, which helps to reduce analysis time and improves reproducibility.

Inhibition of complement activation by CD55 overexpression in human induced pluripotent stem cell derived kidney organoids.

End stage renal disease is an increasing problem worldwide driven by aging of the population and increased prevalence of metabolic disorders and cardiovascular disease. Currently, kidney transplantation is the only curative option, but donor organ shortages greatly limit its application. Regenerative medicine has the potential to solve the shortage by using stem cells to grow the desired tissues, like kidney tissue. Immune rejection poses a great threat towards the implementation of stem cell derived tissues and various strategies have been explored to limit the immune response towards these tissues. However, these studies are limited by targeting mainly T cell mediated immune rejection while the rejection process also involves innate and humoral immunity. In this study we investigate whether inhibition of the complement system in human induced pluripotent stem cells (iPSC) could provide protection from such immune injury. To this end we created knock-in iPSC lines of the membrane bound complement inhibitor CD55 to create a transplant-specific protection towards complement activation. CD55 inhibits the central driver of the complement cascade, C3 convertase, and we show that overexpression is able to decrease complement activation on both iPSCs as well as differentiated kidney organoids upon stimulation with anti-HLA antibodies to mimic the mechanism of humoral rejection.

Successful combined auxiliary partial liver and intestinal transplantation in two highly sensitized, cross-match positive patients.

Sensitization to human leukocyte antigen (HLA) creates an immunological barrier to intestinal transplantation (ITx). Current desensitization therapies are limited and ineffective in the most highly sensitized patients. A co-transplanted whole liver transplant can protect a kidney, heart, or intestinal allograft from antibody-mediated injury. Whether an auxiliary partial liver allograft provides effective protection for highly sensitized intestinal transplant recipients is unknown. Two patients with strong HLA donor-specific antibody at high titer against their deceased donors underwent combined auxiliary partial liver and ITx across a positive cross-match. The left lateral lobes from the combined-graft recipients and the right liver lobes from the deceased donors were transplanted as a domino procedure to other four patients. Two combined-graft recipients have had an uneventful postoperative course without major complications at a 12- and 24-month follow-up, respectively. Intestinal graft function has been excellent with no evidence of humoral or cellular rejection. While a positive cross-match turned negative, titers of donor-specific HLA antibodies gradually declined over time after transplant. The left liver lobes procured from the combined-graft recipients were successfully transplanted into two pediatric patients (age 1.9, 2.4years) and the right lobes from two deceased donors were successfully transplanted into two adult patients. All transplant procedures went well, without post-operative complications related to the splitting technique. Our results indicate that an auxiliary liver transplant can effectively protect a co-transplanted intestinal allograft against rejection and suggest that this combined procedure may serve as a useful therapeutic adjunct for a highly sensitized intestinal transplant candidate.

Successful Deceased Donor Kidney Transplantation in a Highly Sensitized Patient after Reclassification of Unacceptable Antigens Based on HLA Epitope Analysis

For patients with end stage renal disease, kidney transplant offers significant survival and quality-of-life advantages compared with dialysis. But for patients seeking transplant who are highly sensitized, waiting times have traditionally been long and options limited. We present the case of a 34-year-old hypersensitized female who underwent renal retransplantation. Histocompatibility tests revealed a calculated panel-reactive antibody of 99.53% with multiple antibodies against class I and II human leucocyte antigens and an eplet analysis was performed. The donor’s potential unacceptable antigens were re-defined and the calculated panel-reactive antibody decreased to 88.38%. After one month the patient received a deceased-donor kidney transplant. Complement dependent cytotoxicity crossmatch was negative; virtual crossmatch and flow cytometry crossmatch with historical serum were positive. High-dose intravenous immunoglobulin and rituximab were added to the thymoglobulin-based induction immunosuppression. Three donor-specific antibodies were detected and plasmapheresis was performed. Renal allograft biopsy revealed no manifestations of rejection. Repeated testing observed a decrease in donor-specific antibodies median fluorescence intensity values. Four months post-transplant, the patient remained with normal graft function without proteinuria. She is receiving a standard maintenance immunosuppression regime with prednisolone, mycophenolate mofetil and tacrolimus. The careful discussion among the transplantation center and histocompatibility laboratory in association with intense immunosuppression and close laboratory monitoring allowed a successful human leukocyte antigen-incompatible deceased donor kidney transplantation in the most critical phase for the occurrence of humoral rejection. It is noteworthy that the new histocompatibility and immunogenetics methodologies provide a more affirmative and comprehensive assessment of mismatch acceptability.

373 ADONHERS (AGED DONOR HEART RESCUE BY STRESS ECHO) PROTOCOL FOR HEART DONATION FROM MARGINAL DONOR HEARTS: MONOCENTRIC RETROSPECTIVE STUDY ON RECIPIENT'S SURVIVAL AFTER 10-YEAR FOLLOW-UP

Abstract Backgorund Amelioration of therapies and increased survival in heart failure (HF) is leading to a growing number of patients affected by advanced HF, with an overall 1-year prognosis ranging from 25 to 75%. The gold standard treatment for end stage HF is heart transplantation (Htx), but lack of organs donors remains an important limitation. Marginal hearts can potentially improve and be utilized after a re-evaluation by “aggressive” assessment of donor left ventricular function. Purpose In our study we analysed if recipients of marginal donor hearts, selected by dipyridamole stress echocardiography, had different outcome compared to recipients with acceptable donor hearts. Methods Data collected from 2006 and 2014 of patients who received orthotopic Htx from marginal heart donors (group 1) and were retrospectively analysed and compared with recipients of acceptable heart donors (group 2). Bedside standard echocardiography and dipyridamole stress echo was performed for the selection of marginal hearts &amp;gt; 55 years old or &amp;lt; 55 with comorbidities/mildly dysfunctional left ventricle. Clinical, laboratory and instrumental features of the two groups of recipients were evaluated and patients with homogenous baseline characteristics were selected to reduce biases among the two groups. Follow-up through routine heart transplant surveillance included visit, echocardiography, blood tests, serial endomyocardial biopsies and coronary angiography. Results Twenty-two recipients were included in the study. Mean donors age was 41 ± 23, 45 ± 29 years for group 1 vs 36 ± 12 for group 2. The average follow-up was 113 months. Age, cardiovascular risk and morpho-functional characteristics of the left ventricle were comparable between the two population (P&amp;gt; 0.05). Left atrial size was significantly higher in marginal hearts (Optimal: p=0.007; Marginal: p=0.003). Acceptable recipients showed a higher impact of CAV (p= 0.019) together with more elevated values of cholesterol and triglycerides (p = 0.048 and p = 0.012 respectively). No differences concerning cellular or humoral rejection were found between the two groups. Four patients deceased, 3 had received a standard donor heart and 1 was from the marginal donor group, with and overall median time to death of 124 months. Conclusions Our small pilot study shows how the evaluation of marginal donor hearts with echo stress result to no affect recipients survival compared with controls of acceptable hearts. A well-controlled selection of marginal hearts could therefore improve the shortage of organs, reducing the long line of patients waiting for a heart.