Chronic Antibody-mediated Rejection Research Articles

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.

C1q-Fixing De Novo Donor Specific Antibodies in Therapeutic Management of Chronic Antibody-Mediated Rejection Postkidney Transplantation

Evidence for C1q-fixing donor-specific antibodies (DSA) after chronic antibody-mediated rejection (CABMR) treatment is lacking. We investigated if C1q-DSA could predict therapy response in patients with biopsy-proven CABMR. Twenty kidney transplant patients with late-onset DSA were enrolled. Patients with biopsy-proven CABMR received three plasma pheresis sessions, one dose of rituximab (375 mg/m2), and steroid pulse therapy. We monitored IgG-DSA, C1q-DSA, and renal graft function for >2 years post-CABMR treatment. Patients with C1q-DSA mean fluorescence intensity (MFI) decreased by less than 50% post-treatment were classified as C1q-nonresponders. We compared Banff classification scores (g, ptc, cg, c4d) before and 6 months after treatment. Fourteen (70%) of 20 patients were C1q-DSA positive. The MFIs of IgG-DSA and C1q-DSA before treatment were significantly higher in the C1q-DSA positive group than in the negative group, at 20,035 and 10,918 (P = .008) and 17,702 and 21 (P < .001), respectively. Fifteen patients (75%) were diagnosed with CABMR via biopsy, and 12 patients received rejection therapy. Five (41.7%) patients were C1q-responders and seven (58.3%) were C1q-nonresponders. The MFIs of C1q-DSA before treatment were not significantly different between the two groups (11,521 vs. 13,985). Renal graft function was stable after treatment in C1q-responders for 3 years. In contrast, renal graft function tended to deteriorate in C1q-nonresponders. Biopsy showed improvement in scores in 75% of C1q-responders while deterioration in scores in 42.9% of C1q-nonresponders. C1q-DSA may be a good predictor of outcomes after CABMR treatment.

Histopathologic Remission of Severe Diabetic Nephropathy of Donor Kidney After Kidney Transplantation: A Case Report

Although diabetes is not an absolute contraindication for kidney donation, donor kidneys with severe diabetic nephropathy (DN) are frequently discarded. Current experience with the use of donor kidneys with severe DN is limited. Herein, we report a case of deceased donor kidney with Renal Pathology Society (RPS) classification scheme class III DN transplanted to a female recipient without post-operative hyperglycemia. Although kidney allograft biopsy still showed class III DN at 6 months, it turned to RPS class IIa DN combined with chronic antibody-mediated rejection at 4.5 years and 9 years. At the last follow-up approximately 10 years after transplantation, the patient's serum creatinine was 2.27 mg/dl. Our case indicates that with careful selection of potential recipients, favorable clinical outcomes can be achieved even with donor kidneys with severe DN. Thus, RPS class III diabetic donor kidneys deserve further evaluation and should not always be discarded.

Podocyte Injury in Kidney Allograft with Chronic Antibody-Mediated Rejection: Late Occurrence and Association with Glomerular Basement Membrane Thickening

Podocyte Injury in Kidney Allograft with Chronic Antibody-Mediated Rejection: Late Occurrence and Association with Glomerular Basement Membrane Thickening

Extended Experience of Belatacept Conversion in Kidney Transplant Patients with Chronic Active Antibody-Mediated Rejection

Extended Experience of Belatacept Conversion in Kidney Transplant Patients with Chronic Active Antibody-Mediated Rejection

Clazakizumab in Chronic Active Antibody-Mediated Kidney Transplant Rejection: Results of the IMAGINE Phase 3 Study

Clazakizumab in Chronic Active Antibody-Mediated Kidney Transplant Rejection: Results of the IMAGINE Phase 3 Study

Unbiased Proteomics Distinguishes Chronic and Acute Antibody-Mediated Rejection in Donor-Specific Antibody-Positive Kidney Transplant Recipients

Unbiased Proteomics Distinguishes Chronic and Acute Antibody-Mediated Rejection in Donor-Specific Antibody-Positive Kidney Transplant Recipients

Therapeutic Apheresis in Pediatric Renal Transplant Recipients.

Clear guidelines for therapeutic apheresis in children after renal transplant do not exist. This article reviews the current experiences with therapeutic apheresis in pediatric transplant recipients. The ideal characteristics of removable substances should have all of the following criteria for an effective therapeutic apheresis: large molecular weight (>15 kDa), prolonged half-life, rapid elimination from the plasma, high intravascular distribution, and low turnover rate. Among these molecules, immunoglobulin M is ~75% intravascular; thus, only 1 or 2 therapeutic apheresis procedures are needed to reduce immunoglobulin M levels efficiently. In contrast, immunoglobulin G is distributed 45% intravascularly and returns to ~60% of preapheresis level within 48 hours; thus, the regimen involves 5 procedures and immunosuppressive therapy is crucial to reduce immunoglobulin G levels. Therapeutic apheresis can also remove cytokines. Immunomodulatory effects of therapeutic apheresis do not only remove unwanted substances but involve other important mechanisms, including increased T-regulatory cells compared with T-effector cells. Many modalities of therapeutic apheresis are used for pediatric transplant recipients, including plasmapheresis, double filtration plasmapheresis, photopheresis, lipopheresis, and immunoadsorption, which is the most effective but has a high cost. Therapeutic apheresis in pediatric transplant recipients is effective for posttransplant nephrotic syndrome (mainly focal segmental glomerulosclerosis). Therapeutic apheresis has also resulted in partial or complete remission for 66% of patients with atypical hemolytic uremic syndrome and 75% response rate for chronic antibody-mediated rejection. However, therapeutic apheresis should be accompanied by other immunosuppressive drugs to prevent rebound phenomena. Potential complications of therapeutic apheresis in pediatric transplant recipients include fluid and electrolyte imbalances, infection, bleeding, and reactions to replacement fluids during therapeutic apheresis. However, therapeutic apheresis (combined with immunosuppression) is an effective tool in most pediatric renal transplant recipients for management of antibody-mediated rejection, focal segmental glomerulosclerosis, and atypical hemolytic uremic syndrome.

Innate Immune Cells, Memory T Cells, and Interferon Gamma Responses Characterize Transplant Glomerulopathy of Chronic Antibody-Mediated Rejection

Innate Immune Cells, Memory T Cells, and Interferon Gamma Responses Characterize Transplant Glomerulopathy of Chronic Antibody-Mediated Rejection

Incidence, risk factors, management strategies, and outcomes of antibody-mediated rejection in pediatric kidney transplant recipients-a multicenter analysis of the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN).

This study by the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) was designed to determine the incidence, risk factors, current management strategies, and outcomes of antibody-mediated rejection (ABMR) in pediatric kidney transplant recipients (pKTR). We performed an international, multicenter, longitudinal cohort study of data reported to the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) registry. Three hundred thirty-seven pKTR from 21 European centers were analyzed. Clinical outcomes, including kidney dysfunction, rejection, HLA donor-specific antibodies, BK polyomavirus-associated (BKPyV) nephropathy, and allograft loss, were assessed through 5years post-transplant. The cumulative incidence of de novo donor-specific class I HLA antibodies (HLA-DSA) post-transplant was 4.5% in year 1, 8.3% in year 3, and 13% in year 5; the corresponding data for de novo class II HLA-DSA were 10%, 22.5%, and 30.6%, respectively. For 5years post-transplant, the cumulative incidence of acute ABMR was 10% and that of chronic active ABMR was 5.9%. HLA-DR mismatch and de novo HLA-DSA, especially double positivity for class I and class II HLA-DSA, were significant risk factors for ABMR, whereas cytomegalovirus (CMV) IgG negative recipient and CMV IgG negative donor were associated with a lower risk. BKPyV nephropathy was associated with the highest risk of graft dysfunction, followed by ABMR, T-cell mediated rejection, and older donor age. This study provides an estimate of the incidence of de novo HLA-DSA and ABMR in pKTR and highlights the importance of BKPyV nephropathy as a strong risk factor for allograft dysfunction.

P.036: Comparative profiles of circulating T-cell subsets and cytokines in Kidney allograft recipients with inflammatory interstitial fibrosis and tubular atrophy and Chronic antibody-mediated rejection.

P.036: Comparative profiles of circulating T-cell subsets and cytokines in Kidney allograft recipients with inflammatory interstitial fibrosis and tubular atrophy and Chronic antibody-mediated rejection.

205.5: Not all transplant glomerulopathy related to chronic antibody-mediated rejection.

205.5: Not all transplant glomerulopathy related to chronic antibody-mediated rejection.

A Population Pharmacokinetic Model of Tocilizumab in Kidney Transplant Patients Treated for Chronic Active Antibody-Mediated Rejection: Comparison of Plasma Exposure Between Intravenous and Subcutaneous Administration Schemes.

Tocilizumab prevents the clinical worsening of chronic active antibody-mediated rejection (CAAMR) in kidney transplant recipients. Following a global shortage of the intravenous pharmaceutical form in 2022, patients were switched from monthly intravenous administration of 8 mg/kg to weekly subcutaneous injection of 162 mg, raising the question of bioequivalence between these schemes of administration. We aimed to compare the areas under the curve (AUC) of tocilizumab in virtual simulations of populations treated with the two administration schemes and to identify the covariates that could contribute to pharmacokinetic variability of tocilizumab in kidney transplant patients with CAAMR who received tocilizumab as salvage treatment. This retrospective monocentric study included 43 kidney transplant patients (202 tocilizumab concentrations) with CAAMR treated with intravenous or subcutaneous tocilizumab between December 2020 and January 2023. We developed a population pharmacokinetic model using nonlinear mixed effects modeling and identified the covariates that could contribute to tocilizumab AUC variability. Monte Carlo simulations were then performed to assess the subcutaneous and intravenous tocilizumab AUC for 0-28 days (M1), 56-84 days (M3), 140-168 days (M6), and 308-336 days (M12). Bioequivalence was defined by SC/IV AUC geometric mean ratios (GMRs) between 0.80 and 1.25. A two-compartment model with parallel linear and nonlinear elimination best described the concentration-time data. Significant covariates for tocilizumab clearance were body weight, urinary albumin-to-creatinine ratio (ACR), and inflammation status [C-reactive protein (CRP) ≥5 mg/L]. The GMR values and their 90% confidence intervals at M3, M6, and M12 were within the 0.8-1.25 margin for equivalence. Conversely, the 90% prediction intervals of the GMR were much wider than the 90% confidence intervals and did not fall within 0.8 and 1.25. From month 3 of treatment, the subcutaneous and intravenous tocilizumab administration schemes provided average bioequivalent pharmacokinetic exposure at the population level but not at the individual level. Body weight, inflammation, ACR, and administration scheme should be considered to personalize the dose of tocilizumab for patients with CAAMR. Further studies are required to determine the target of tocilizumab exposure in kidney transplant patients with CAAMR.

Use of Tocilizumab in the treatment of chronic active antibody-mediated rejection in pediatric kidney transplant recipients

Chronic active antibody-mediated rejection is one of the leading causes of graft failure and traditional therapies have unclear efficacy. Recent studies suggested that Tocilizumab could stabilize renal function and improve microvascular inflammation. Here we report the outcomes of Tocilizumab therapy in 6 pediatric kidney transplant recipients with biopsy-proven chronic active antibody-mediated rejection resistant to standard treatments. All patients received monthly Tocilizumab infusions for 6 months and were monitored for renal function (creatinine, estimated glomerular filtration rate (eGFR), proteinuria) and Human Leukocyte Antigens (HLA) and non-HLA antibodies at baseline and 3 and 6 months after Tocilizumab initiation. For each patient, a follow-up biopsy was scheduled at the end of the treatment. Renal function did not show stabilization or improvement (mean eGFR 37 ml/min/1.73 m2 pre-Tocilizumab and 27 ml/min/1.73 m2 3 months after-Tocilizumab) and proteinuria remained stable. Moreover, Tocilizumab had no impact on HLA and non-HLA antibodies. Graft loss was observed in 3 patients (50 %) and 4 patients who underwent post-treatment biopsy showed a worsening in overall chronicity scores. In our pediatric series, rescue therapy with Tocilizumab did not appear to be effective in modifying the natural history of chronic active antibody-mediated rejection.

Antibody-mediated rejection in post-liver transplant clinical care: Are we there yet for timely diagnosis and treatment?

With improvements in medical management and surgical technique in the field of solid organ transplantation, many historically prominent causes of liver allograft injury have been ameliorated or, in the case of Hepatitis C virus, eliminated altogether. In this transformed clinical landscape, antibody-mediated rejection (AMR) has emerged as a defining barrier to maintenance of long-term liver allograft function. The liver's unique anatomy, high regenerative capacity, and tolerogenic immunological environment tend to mitigate the severest AMR manifestations. Consequently, the clinical importance of AMR in the liver has been recognized more slowly than for other solid organ allografts. Significant strides have been made in elucidating clinical and histopathologic features of acute and chronic liver AMR, with the Banff 2016 criteria among the most notable. However, current histopathologic definitions of AMR are lacking in sensitivity and specificity. C4d staining is an imperfect biological surrogate for antibody-mediated injury, and suffers from significant technical limitations. The frequent co-occurrence of T cell mediated rejection and non-immunologic allograft damage (including recurrence of primary disease) also hinders definitive identification of AMR and results in misattribution of its effects. The goal of this review is to summarize the current understanding of AMR in the context of liver transplantation, including risk factors, pathogenesis, and current diagnostic and treatment strategies. Potential directions of future research are also addressed.

Unveiling Spatial Immune Cell Profile in Kidney Allograft Rejections Using 36-plex Immunofluorescence Imaging.

Kidney allograft rejections are orchestrated by a variety of immune cells. Because of the complex histopathologic features, accurate pathological diagnosis poses challenges even for expert pathologists. The objective of this study was to unveil novel spatial indices associated with transplant rejection by using a spatial bioinformatic approach using 36-plex immunofluorescence image data. The image obtained from 11 T cell-mediated rejection (TCMR) and 12 antibody-mediated rejection (AMR) samples were segmented into 753 737 single cells using DeepCell's Mesmer algorithm. These cells were categorized into 13 distinct cell types through unsupervised clustering based on their biomarker expression profiles. Cell neighborhood analysis allowed us to stratify kidney tissue into 8 distinct neighborhood components consisting of unique cell type enrichment profiles. In contrast to TCMR samples, AMR samples exhibited a higher frequency of neighborhood components that were characterized by an enrichment of CD31+ endothelial cells. Although the overall frequency of CD68+ macrophages in AMR samples was not significantly high, CD68+ macrophages within endothelial cell-rich lesions exhibited a significantly higher frequency in AMR samples than TCMR samples. Furthermore, the frequency of interactions between CD31+ cells and CD68+ cells was significantly increased in AMR samples, implying the pivotal role of macrophages in AMR pathogenesis. Importantly, patients demonstrating a high frequency of CD31:CD68 interactions experienced significantly poorer outcomes in terms of chronic AMR progression. Collectively, these data indicate the potential of spatial bioinformatic as a valuable tool for aiding in pathological diagnosis and for uncovering new insights into the mechanisms underlying transplant rejection.

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.

Granulomatous Tubulointerstitial Nephritis in a Kidney Allograft: Treatment with Interleukin-6 Receptor Antagonist Stabilises Kidney Function

Granulomatous tubulointerstitial nephritis (GTIN) attributed to early onset sarcoidosis is an ultrarare finding in an allograft kidney biopsy. We present the case of a young man with allograft dysfunction who had GTIN upon biopsy. We performed a thorough case review based on recovered records from early childhood and reassessed genetic testing results. We revised his underlying diagnosis from cryopyrin-associated periodic syndrome to early-onset sarcoidosis with wild-type NOD2 and established a rationale to use the interleukin-6 (IL-6) receptor blocker tocilizumab (TCZ). This suppressed his inflammatory disease and stabilised kidney function. We performed a literature review related to the emerging role of IL-6 pathway blockade in kidney transplantation. We identified 18 reports with 417 unique patients treated with TCZ for indications including HLA-desensitisation, transplant immunosuppression induction, treatment of chronic antibody-mediated rejection, and treatment of subclinical rejection. Both TCZ and the direct IL-6 inhibitor clazakizumab are being studied in ongoing randomised control trials.

#725 Incorporating molecular rejection patterns to differentiate histologic activity and chronicity features in antibody-mediated rejection

Abstract Background and Aims Biopsy-based transcripts associated with antibody-mediated rejection (AMR) hold promise as substitutes for C4d positivity, according to the Banff Meeting Report of 2022. However, incorporating histologic and molecular features of disease activity and chronicity is crucial to potentially guide patient management. Method We analyzed 365 kidney allograft biopsies by histology and the Molecular Microscope Diagnostic System (MMDx) at the University Hospital Zurich from July 2021 to November 2023. Histologic findings were classified according to Banff 2022 into (1) active AMR (n = 24), (2) chronic active AMR (MVI, n = 47), and (3) chronic AMR (n = 30). The corresponding histologic subgroups with DSA negativity were used for comparison. Results Fourteen out of 24 cases (58%) with active AMR, 28 of 47 cases (60%) with chronic active AMR, but only 1 of 30 cases (3%) with chronic AMR showed molecular AMR. Among cases with molecular AMR the sum of the fully-developed AMR-related (R5) and late-stage AMR-related (R6) phenotype scores was significantly higher in chronic active AMR compared to active AMR cases (p = 0.0017). This finding was even more pronounced in chronic active AMR cases with double contours (cg)&amp;gt;1 (p = 0.00062). Similarly, in the cases without molecular AMR the sum of the fully-developed AMR-related (R5) and late-stage AMR-related (R6) phenotype scores was higher in chronic active AMR compared to active AMR cases (p = 0.039) and more pronounced in cases with cg&amp;gt;1 (p = 0.008). However, rejection phenotype scores (R1-R6) among chronic AMR cases did not differ from DSA-positive or DSA-negative cases without microvascular inflammation (p = 0.705 for R5+R6). Conclusion Incorporating molecular rejection phenotype patterns may further differentiate disease activity and chronicity in cases with active and chronic active AMR by histology. However, molecular subthreshold findings do not appear relevant in chronic AMR cases.

#1492 Metabolic switch in CD8+ T cells may influence immune response in chronic antibody-mediated rejection (CAMR)

Abstract Background and Aims CAMR is the main cause of chronic graft injury and subsequent graft loss, but its pathogenesis is still largely unclear. Our group demonstrated an increase in CD8+ T cells infiltrating biopsies from CAMR patients (PMID: 20595199), but their role remains to be defined. Recently, immunometabolism has emerged as a field connecting cell energy metabolism with the immune cell differentiation and functions. Particularly, the permanent aerobic glycolysis of CD8+ lymphocytes induces their transition from naïve to activated state and effector T cells (PMID: 37315709). Thus, the aim of the study was to investigate the molecular mechanisms underlying the development of CAMR by the analysis of gene expression profiles of CD8+ T lymphocytes in conjunction with their metabolic state. Method We enrolled 14 patients with biopsy-proven CAMR and 12 stable transplant recipients with normal graft histology and function (control group). CD8+ T cells were purified by CD8 MicroBeads (Miltenyi Biotec) then counted (TC20™ Automated Cell Counter). Gene expression profiles of CD8+ T lymphocytes isolated from both groups were assessed using Agilent microarrays. Data obtained were statistically and functionally evaluated (IPA software) and validated by qPCR. Oxygen consumption rate (OCR) in CD8+ and CD8- cells was measured by a Resipher oxygen sensing lid (Lucid Scientific Inc., USA). The contribution of mitochondrial respiration to OCR was investigated in isolated CD8+ T cells from CAMR and controls treated with rotenone/antimycin A (Rot/AA), oligomycin (Olygo) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) to evaluate spare respiratory capacity (SRC), ATP-linked respiration, proton leak and maximal respiration. Results Gene expression profiles of CD8+ T cells showed a characteristic alteration of lipid metabolism in CAMR patients with the triglyceride biosynthesis pathway (p = 2.69E-3) as the most altered pathway and several genes de-regulated all potentially involved in the altered metabolic state of CD8+ T cells. Among others, we validated the increased expression of Nicotinamide Phosphoribosyltransferase (NAMPT) (FC = +2.39), the rate-limiting enzyme of nicotinamide adenine dinucleotide (NAD+) salvage pathway involved in the glycolysis progression, mostly activated in effector T cells. We then decided to evaluate the OCR and the metabolic state of CD8+T cells. Basal OCR was higher in CD8+ rather than CD8- cells, but with different trends among cells isolated from control and CAMR patients. Indeed, CD8+ cells from CAMR patients showed higher OCR compared to control, while OCR was lower in CD8- from CAMR rather than control patients. CD8+ OCR from both CAMR and control patients was mostly dependent on mitochondrial respiration, since it was deeply reduced by Rot/AA treatment. Interestingly, inhibitory response to Oligo treatment by CD8+ cells from CAMR patients was modest, while OCR was noticeably stimulated by FCCP in these cells, suggesting that mitochondrial oxygen uptake was not ATP linked but rather associated with increased uncoupling. These data suggest that CD8+ T cells from CAMR patients are activated effector T cells primarily utilizing aerobic glycolysis. To confirm this hypothesis, we evaluated the gene expression levels of: i) HIF1a, which involves permanent dependence on glycolysis even in the presence of oxygen (Warburg effect); ii) fatty acid transporter CD36, whose levels mimic an energy dependence on the beta oxidation of fatty acids, a process activated in memory T cells. We confirmed an increased expression of HIF1a and a reduced expression of CD36 in CD8+T cells from CAMR patients compared to controls (p&amp;lt;0.05), that confirm the T effector phenotype. Conclusion Our data suggest that CD8+ T cell from CAMR patients showed permanent dependency on glycolysis leading to altered immune phenotype and response, thus indicating novel opportunities to modulate the immune system for therapeutic purposes in kidney transplanted patients and reduce graft rejection.