Renal Transplant Biopsies Research Articles

Clinical analysis of seven cases of primary hyperoxaluria type 1

We retrospectively analyzed the clinical data of seven patients (four men and three women) with primary hyperoxaluria (PH) type 1 (PH1) in the Department of Nephrology of Zhongda Hospital, Southeast University from January 2018 to October 2023. The mean age at disease onset was 32.1 (range: 26-42) years. The mean age at diagnosis was 40.6 (range: 28-51) years. All patients initially had kidney stones, and three patients were found to have renal insufficiency at the time of disease onset. Among them, two patients underwent hemodialysis immediately. Symptoms at the first visit included bone pain (n=7), joint pain or deformity (n=5), fatigue (n=5), hypotension (n=3), and subcutaneous nodules (n=2). Four patients had a family history of PH. All patients had varying degrees of anemia (60-114 g/L), significant hypoalbuminemia (16.5-32.1 g/L), and hypercoagulable state (D-dimer: 2 230-12 781 μg/L). Seven patients received maintenance hemodialysis; their mean age was 37.7 (range: 26-50) years. The mean duration from disease onset to hemodialysis was 5.6 (range: 0-20) years. Five patients repeatedly experienced dialysis access dysfunction. Three patients underwent kidney transplantation before a diagnosis was made, and all transplanted kidneys lost function due to oxalate deposition. The mean follow-up duration was 14.43 (range: 4-38) months. Unfortunately, one patient died. All seven patients underwent computed tomography of the abdomen. All patients suffered skeletal abnormalities, bilateral nephrolithiasis, and nephrocalcinosis. Six patients carried AGXT gene mutations, including four compound heterozygous mutations and two pure homozygous mutations.The mutation sites included: c.823-824dup.AG (p.S275Rfs*38)(exon 8), c.815-816ins.GA (p.S275Rfs*38)(exon 8), c.595G>A (p.G199S) (exon 5), c.32C>G (p.P11R) (exon 1), and c.638C>T (p.A213V)(exon 6). According to the American College of Medical Genetics and Genomics guidelines, two loci were identified as likely pathogenic variants, seven were identified as pathogenic variants, and one locus was identified as having uncertain significance. In addition, patients 1 and 4 underwent skin biopsy, patient 2 underwent renal transplant biopsy, and patient 3 underwent bone marrow biopsy. Interestingly, significant oxalate deposition was found in the tissues. Therefore, PH1 is a rare autosomal recessive inherited disease. This study not only enhanced the understanding of the clinical characteristics of PH1 patients but also had great significance in early diagnosis and treatment of the disease.

Interstitial Foci Expression of Indoleamine 2,3-Dioxygenase 1: A Potential Biomarker for Kidney Transplant Rejection.

(1) Background: Kidney transplantation is the best therapy for patients with end-stage renal disease, but the risk of rejection complicates it. Indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme involved in immune response modulation, has been suggested to play a role in transplant immunological injury. The aim of the study was to explore the expression of IDO1 in the interstitial foci of transplanted kidneys and its potential association with rejection episodes. (2) Methods: This retrospective study analysed kidney transplant biopsies from 121 patients, focusing on IDO1 expression in interstitial foci. Immunohistochemistry was used to detect IDO1, and patients were categorised based on IDO1 presence (IDO1-IF positive or negative). The incidence of rejection was compared between these groups. (3) Results: Patients with IDO1 expression in interstitial foci (IDO1-IF(+)) exhibited higher incidences of rejection 46/80 (57.5%) vs. 10/41 (24.34%) patients compared to IDO1-IF(-) patients, which was statistically significant with p = 0.0005. The analysis of antibody-mediated rejection showed that IDO1-IF(+) patients developed AMR at 12/80 (15%), while only 1 IDO1-IF(-) negative patient did (2,44%), with p = 0.035. T-cell-mediated rejection was also more common in IDO1-IF(+) patients 43/80 (53.75%) than in IDO1-IF(-) patients 7/41 (17.07%), with p = 0.0001. (4) Conclusions: IDO1 expression in interstitial foci of renal transplant biopsies is associated with a higher incidence of rejection, suggesting that IDO1 could serve as a potential biomarker for transplant rejection. These findings highlight the importance of IDO1 in immune regulation and its potential utility in improving the management of kidney transplant recipients.

Roles of M1 and M2 macrophage infiltration in post-renal transplant antibody-mediated rejection

BackgroundWe aimed to analyze the roles of M1 and M2 macrophage infiltration in post-renal transplant antibody-mediated rejection (AMR). MethodsA total of 102 recipients who underwent renal allotransplant from January 2020 to February 2023 were divided into an immune tolerance group (n = 56) and a rejection group (n = 46). The transplant renal biopsy specimens were harvested by ultrasound-guided puncture. The M1 and M2 macrophages in renal tissues were counted, and the M1/M2 ratio was calculated. The numbers of M1 and M2 macrophages and M1/M2 ratios in patients with different severities of interstitial fibrosis/tubular atrophy (IF/TA) and different degrees of tubulointerstitial inflammatory cell infiltration were compared. The predictive values of M1 and M2 macrophages and M1/M2 ratio for post-renal transplant AMR were clarified. ResultsThe rejection group had significantly more M1 and M2 macrophages and higher M1/M2 ratio than those of the immune tolerance group (P < 0.05). In the rejection group, infiltrating macrophages were mainly distributed in the glomerular and interstitial capillaries, with M1 macrophages being the predominant type. With increasing severity of IF/TA, the numbers of M1 and M2 macrophages and M1/M2 ratio rose in patients with post-renal transplant AMR (P < 0.05). The numbers and ratio had significant positive correlations with the levels of blood urea nitrogen and serum creatinine (P < 0.05). The areas under the curves (AUCs) of numbers and M1 and M2 macrophages and M1/M2 ratio for predicting post-renal transplant AMR were 0.856, 0.839 and 0.887, respectively. The combined detection had AUC of 0.911 (95% CI: 0.802–0.986), sensitivity of 90.43% and specificity of 83.42%. ConclusionsSignificant macrophage infiltration is present in the case of post-renal transplant AMR, and closely related to the severity of IF/TA and the degree of tubulointerstitial inflammatory cell infiltration.

#2566 Clinicopathological and molecular characteristics of plasma cell rich rejection in renal transplant biopsies

Abstract Background and Aims Plasma cell rich rejection (PCRR) is an uncommon, ill-defined type of renal allograft rejection in the literature considered as a subtype of T cell-mediated rejection (TCMR). PCRR has poorer clinical outcome and is often refractory to classic immunosuppressive therapy. Our study analyzed In this study, we analyzed PCRR in a large cohort of patients who underwent renal transplantation at the Amsterdam UMC. Our objective was to study clinical, histological and molecular signatures of PCRR in comparison to other types of rejection, especially late presentations of TCMR and ABMR. We hypothesized PCRR could be a specific subtype of allograft rejection with different molecular and cellular characteristics compared to (late) TCMR and ABMR with differences in clinical outcome. Method We retrospectively scored and reclassified the last known biopsy of 263 renal transplant recipients, morphologically classified as rejection according to the 2019 Banff classification. mRNA expression analysis was performed using the Nanostring B-HOT panel on a subset of cases. PCRR was compared to (late) TCMR, ABMR and mixed rejection for renal function follow-up and graft survival. Results mRNA analysis revealed uniquely expressed genes in PCRR including LOX, CPA3, IL4, IL17F, and MMP12. PCRR is enriched for genes related to mast cells, memory B- and T-cells and transcripts involved in NK cells and allograft fibrosis with heterogeneity in gene expression in biopsies with PCRR. PCRR might be a late event compared to late TCMR and ABMR, with a higher degree of total inflammation and fibrosis. Graft survival and kidney function was similar to late TCMR and ABMR during a 5-year follow-up period after renal biopsy Conclusion PCRR represents a distinct late-onset stage of inflammation displaying diverse gene expression patterns, with presence of mainly mast cells, NK cells and transcripts involved in renal allograft fibrosis. Such insights could enable a better and more tailored treatment for these patients and ultimately enhance long-term graft survival for patients affected by PCRR. Clinical outcomes in patients with PCRR appeared similar to late TCMR and ABMR.

Exploring kidney allograft rejection: A proof-of-concept study using spatial transcriptomics

In this proof-of-concept study, spatial transcriptomics combined with public single-cell ribonucleic acid-sequencing data were used to explore the potential of this technology to study kidney allograft rejection. We aimed to map gene expression patterns within diverse pathologic states by examining biopsies classified across nonrejection, T cell–mediated acute rejection, interstitial fibrosis, and tubular atrophy. Our results revealed distinct immune cell signatures, including those of T and B lymphocytes, monocytes, mast cells, and plasma cells, and their spatial organization within the renal interstitium. We also mapped chemokine receptors and ligands to study immune cell migration and recruitment. Finally, our analysis demonstrated differential spatial enrichment of transcription signatures associated with kidney allograft rejection across various biopsy regions. Interstitium regions displayed higher enrichment scores for rejection-associated gene expression patterns than tubular areas, which had negative scores. This implies that these signatures are primarily driven by processes unfolding in the renal interstitium. Overall, this study highlights the value of spatial transcriptomics for revealing cellular heterogeneity and immune signatures in renal transplant biopsies and demonstrates its potential for studying the molecular and cellular mechanisms associated with rejection. However, certain limitations must be borne in mind regarding the development and future applications of this technology.

Mid-term efficacy evaluation of ABO incompatible living relative kidney transplantation based on protocol biopsy

Objective: To evaluate the mid-term efficacy of ABO incompatible living donor kidney transplantation (ABOi-KT) based on the results of routine renal biopsy for transplantation. Methods: Retrospective collection of clinical data from 23 pairs of ABOi-KT donors and recipients at the First Affiliated Hospital of Sun Yat-sen University from July 2015 to November 2021. ABOi-KT was performed on recipients after desensitization treatment, and the results of routine kidney transplant biopsy at 1 week, 1 month, 3 months, 6 months, and 12 months after surgery were analyzed. Combined with blood type antibody levels and renal function recovery, the mid-term efficacy of ABOi-KT was evaluated. Results: Among the 23 recipients, there were 19 males and 4 females; age range from 19 to 47 years old [(29.6±6.7) years old], all underwent ABOi-KT successfully after receiving desensitization treatment. The follow-up time was (44.6±22.4) months, of which 22 cases were followed up for more than 1 year. The incidence rates of rejection reactions at 1 week, 1 month, 3 months, 6 months, and 12 months after surgery were 15.0% (3/20), 11.1% (1/9), 7.7% (1/13), 25.0% (3/12), and 12.5% (1/8), respectively. For receptors with rejection reactions, targeted anti-rejection therapy was performed based on clinical symptoms and various indicators. Borderline T cell mediated rejection (TCMR) can be converted to mild tubular inflammation after anti-rejection treatment. The positive rate of complement C4d in peritubular capillaries was 95.0% (19/20) one week after surgery, and the positive rate of complement C4d was 100% at 3 and 12 months after surgery. The cumulative survival rates at 1, 3, 5, and 7 years after surgery were all 100%. The cumulative survival rates at 1, 3, 5, and 7 years after kidney transplantation were 100%, 93.3%, 84.0%, and 84.0%, respectively. Except for 2 recipients who underwent transplantation in 2017 and experienced kidney failure at 30 and 49 months after surgery, all other transplanted kidneys survived. Conclusions: The results of routine renal transplant biopsy show that ABOi-KT has a good mid-term therapeutic effect. The pathological changes of ABOi-KT can be dynamically observed through routine renal transplant biopsy and targeted treatment for rejection reactions can be provided accordingly.

Expression of Rejection-Associated Transcripts in Early Protocol Renal Transplant Biopsies Is Associated with Tacrolimus Exposure and Graft Outcome.

Subclinical inflammation in protocol biopsies relates to tacrolimus exposure and human leukocyte antigen (HLA) matching. We aimed to characterize transcripts associated with rejection and tacrolimus exposure and the latter's association with transplant outcomes. We tested whether gene expression is associated with rejection using strictly normal protocol biopsies (n = 17) and biopsies with T cell-mediated rejection (TCMR) or antibody-mediated rejection (ABMR) according to Banff criteria (n = 12). Subsequently, we analyzed these transcripts in a set of 4-month protocol biopsies (n = 137) to assess their association with donor and recipient characteristics, the intensity of immunosuppression, and the graft outcome. Differential expression (false discovery rate (FDR) < 0.01, fold (change (FC) > 3) between normal and rejection biopsies yielded a set of 111 genes. In the protocol biopsy cohort (n = 137), 19 out of these 111 genes correlated with tacrolimus trough levels at the time of biopsy (TAC-C0), and unsupervised analysis split this cohort into two clusters. The two clusters differed in donor age and tacrolimus trough levels. Subclinical rejection, including borderline lesions, tended to occur in the same cluster. Logistic regression analysis indicated that TAC-C0 at the time of biopsy (OR: 0.83, 95%CI:0.72-0.06, p = 0.0117) was associated with cluster 2. In a follow-up averaging 70 ± 30 months, this patient group displayed a significant decline in renal function (p = 0.0135). The expression of rejection-associated transcripts in early protocol biopsies is associated with tacrolimus exposure and a faster decline in renal function.

Indoleamine 2,3-Dioxygenase 1 (IDO1) in Kidney Transplantation: A Guardian against Rejection.

Kidney transplantation is a crucial treatment for end-stage kidney disease, with immunosuppressive drugs helping to reduce acute rejection rates. However, kidney graft longevity remains a concern. This study explores the role of indoleamine 2,3-dioxygenase 1 (IDO1) in kidney transplant immunology. IDO1 breaks down tryptophan, affecting immune cell behavior, primarily T-cells. The research focuses on both cellular and antibody-mediated immune responses, often causing graft damage. The study assessed IDO1 expression in renal transplant biopsies from patients with graft function decline, examining its connection to clinical parameters. A total of 121 biopsy samples were evaluated for IDO1 expression using immunohistochemistry. Patients were categorized as IDO1(+) positive or IDO1(-) negative based on immunoreactivity in tubular epithelium. Results showed a significant link between IDO1 expression and rejection incidence. IDO1(+) positive patients had lower rejection rates (32.9%) compared to IDO1(-) negative ones (62.2%) [p = 0.0017], with substantial differences in antibody-mediated rejection (AMR) (5.2% vs. 20%) [p = 0.0085] and T-cell mediated rejection (TCMR) (31.6% vs. 57.8%). These associations suggest that IDO1 may play a protective role in kidney transplant rejection. IDO1 modulation could offer novel therapeutic avenues to enhance graft survival. The study underscores IDO1 as a potential marker for rejection risk assessment, with its potential applications in personalized interventions and improved patient outcomes. Further research is needed to fully comprehend the mechanisms behind IDO1's immunomodulatory functions and its potential clinical translation.

P204 Use of cell-free DNA analysis to determine need for renal transplant biopsy after detection of circulating donor-specific anti-HLA antibodies in renal transplant recipients

P204 Use of cell-free DNA analysis to determine need for renal transplant biopsy after detection of circulating donor-specific anti-HLA antibodies in renal transplant recipients

Research Highlights.

Research Highlights.

Transplant Renal Biopsy Complicated by Arteriovenous Fistula

Transplant Renal Biopsy Complicated by Arteriovenous Fistula

Renal Transplant Biopsies: Recommended Guidelines on Minimum Dataset Reporting

Renal allograft biopsies are essential in posttransplant setting to be able to accurately diagnose graft pathologic changes and help in guiding patient management. Banff schema has been long providing guidance to transplant pathologists to accurately diagnose and score the severity of rejections in allograft biopsies. However, there is no standardized minimal data set to report renal transplant biopsies, thereby making it difficult for renal physicians to understand changes in transplant biopsies to adequately manage patients. The present brief review article shall provide guidelines on minimal data set reporting for renal transplant biopsies to bring uniformity in reporting in the whole country.

Spatial Distribution of Macrophage Subtypes Among Rejection Subtypes in Renal Transplant Biopsies by Dual Immunohistochemistry.

We performed dual immunohistochemistry for CD163/CD34 and CD68/CD34 in 108 renal transplant indication biopsies to investigate the presence and distribution of macrophages in various renal compartments. All Banff scores and diagnoses were revised according to the Banff 2019 classification. CD163 and CD68 positive cell counts (CD163pos and CD68pos) were evaluated in the interstitium, glomerular mesangium, and, within glomerular and peritubular capillaries. The diagnosis was antibody-mediated rejection (ABMR) in 38 (35.2%), T-cell mediated rejection (TCMR) in 24 (22.2%), mixed rejection in 30 (27.8%), and no rejection in 16 (14.8%). Banff lesion scores t , i , and ti were correlated with both CD163 and CD68 interstitial inflammation scores ( r > 0.30; P < 0.05). Glomerular total CD163pos was correlated to Banff lesion scores g and cg ( r > 0.30; P < 0.05). Glomerular total, mesangial, and intracapillary CD68pos were correlated with g ( r > 0.30; P < 0.05). Both glomerular total and peritubular capillary CD68pos were correlated with peritubular capillaritis ( r > 0.30; P < 0.05). Glomerular CD163pos were significantly higher in ABMR compared with no rejection, in mixed rejection compared with no rejection and TCMR. CD163pos in peritubular capillaries was significantly higher in mixed rejection compared with no rejection. Glomerular CD68pos was significantly higher in ABMR compared with no rejection. CD68pos per peritubular capillary was higher in mixed rejection, ABMR, and TCMR compared with no rejection. In conclusion, compared with CD68 positive macrophages, localization of CD163 positive macrophages in various renal compartments seems to be different among rejection subtypes and their glomerular infiltration seems to be more specific for the presence of ABMR component.

Visual interstitial fibrosis assessment as continuous variable in protocol renal transplant biopsies.

In current renal transplant pathology practice interstitial fibrosis is visually assessed in categories according to the Banff classification. As this has a moderate reproducibility, which is little ameliorated by morphometric analysis, we investigated whether visual renal fibrosis assessment is feasible on a continuous scale, i.e. as percentage affected area of the cortex. Protocol renal biopsies taken at transplantation (n=125), three (n=73) and twelve months (n=88) after transplantation were visually scored in categories (Banff), and percentages for interstitial fibrosis (ci). Interobserver variation (ICC and weighted κ) was assessed, and morphometric analysis on Sirus Red stained sections was performed. Correlations between the different methods and their association with donor age and eGFR 1 year and 5 year post transplant were analyzed using Pearson's or Spearman's rho. Interobserver agreement was equivalent for Banffci and %ci (κ0.713 vs. ICC 0.792), and for BanffIF/TA and %IF/TA (κ0.615 vs. ICC 0.743). Both Banffci and %ci were associated with Sirius Red morphometry in three and twelve month. With all three methods, a significant correlation was found between donor age and fibrosis in the implantation biopsy, and between fibrosis in the 12 month biopsy and eGFR at 1 and 5 years (eGFR at 1 year: Sirius Red ρ-0.487, %ci ρ-0.393, Banffci ρ-0.413, all p<0.01, eGFR at 5 years: Sirius Red ρ-0.392, %ci ρ-0.333, Banffci ρ-0.435, all p<0.01. Interstitial fibrosis assessment on a continuous scale can be used next to scoring in categories according to the Banff classification in protocol renal transplant biopsies.

Glomerular macrophage index (GMI) in kidney transplant biopsies is associated with graft outcome.

Macrophages in renal transplants have been shown to participate in antibody-mediated rejection and are associated with impaired renal function. We calculated the glomerular macrophage index (GMI) in a large transplant biopsy cohort, studied its quantity in different diagnostic groups, to clarify its possible impact on graft survival. GMI, defined as the mean number of macrophages in 10 glomeruli, was prospectively quantified in 1440 renal transplant biopsies over a 10-year period. The main histopathological diagnoses were grouped into eight disease entities, and GMI was compared to normal transplant biopsies as the reference group. The impact of GMI on graft survival was analyzed. GMI was highest in chronic (mean 9.4) and active (9.7) antibody mediated rejections (ABMR), mixed rejections (7.6), and recurrent or de novo glomerulonephritis (7.5) and differed significantly from normal transplants (1.3) in almost all diagnostic groups. Hazard ratios for graft loss were significantly increased for all biopsies with GMI ≥1.9 compared to GMI<.5 (reference group) in an adjusted Cox regression model and increased with higher GMI levels. Biopsies with GMI ≥ 4.6 had<60% 10-year graft-survival, compared to>80% with GMI ≤ 1.8. GMI levels were predictive of graft loss independent of histological diagnoses and may guide clinicians to decide follow-up and therapy.

A 39-year-old male who received living kidney from his 62-year-old father, blood group matched and CDC cross match all negative, having acute cell mediated rejection 5 hours after transplant due to low Tacrolimus Trough level: A case report

A young renal transplant recipient received living kidney from his father; the Centers for Disease Control and Prevention (CDC) cross match was all negative. He had oliguria 5 hours after transplant with fever and neutrophil leukocytosis. Doppler ultrasonogram revealed increased cortical echo with increased Resistive Index suggesting acute rejection or acute tubular necrosis. Renal transplant biopsy revealed acute T cell mediated rejection (acute TCMR) Grade IIA. Trough level of Tacrolimus blood level done on Day 5 was very low; therefore, Tacrolimus dose was increased. Therapeutic level achieved after giving 6 mg twice a day with addition of erythromycin. Escalating antibiotics, increasing steroids and Tacrolimus dose saved the transplant kidney.

Focal Segmental Glomerulosclerosis (FSGS) Progressing to Collapsing Glomerulopathy in Renal Transplant Recipients With and Without COVID-19 Infection.

Collapsing glomerulopathy (CGN) secondary to HIV or COVID-19 infection mainly occurs in patients of African American descent due to APOL-1 gene mutations, but CGN is occasionally reported in white patients. CGNs are rarely reported in renal transplant biopsies and their association with idiopathic focal segmental glomerulosclerosis (FSGS) is unclear. Patient #1 was a 48-year-old Caucasian white man who had a renal transplant 8 years ago and was recently diagnosed with COVID-19 infection. Two weeks post infection, his serum creatinine (SCr) increased to 2.01 mg/dL from a baseline of 1.40 mg/dL, and he developed concomitant nephrotic range proteinuria. The first renal transplant biopsy showed FSGS. Four weeks later, his sCr level increased to 2.65 mg/dL with worsening proteinuria, and a second renal transplant biopsy revealed CGN. Patient #2 was a 32-year-old African American man whose native renal biopsy revealed primary FSGS. He received a renal transplant with initial post-transplant sCr level at 1.17 mg/dL. Four months later, his sCr and protein-to-creatinine ratio began to rise. Sequential biopsies revealed that the patient had developed recurrent FSGS, which progressed to show features of CGN. The CGN was further confirmed in his transplant kidney graft at autopsy later. This is the first case report of CGN in a white renal recipient with COVID-19 infection. The pathologic presentations of FSGS progressing to collapsing FSGS in our 2 renal transplant recipients suggest that FSGS and GGN may share a common pathophysiologic mechanism of podocytopathy.

Histological changes associated with early and late renal allograft dysfunction in a large three-center transplant program in Iraq

Introduction: Transplantation is the sole viable option for the long-term survival of patients with end-stage renal disease (ESRD) in low-resourced countries. Objectives: To report the histopathological characteristics of kidney graft dysfunction in a large transplant program of a developing country. Patients and Methods: Renal transplant biopsies were analyzed by the Banff 2017 classification and subdivided into early (≤1 year) or late (&gt;1 year) post-engraftment periods during the 12 months of 2019. Results: Here, 290 satisfactory graft biopsies were obtained on 290 patients for graft failure and/ or proteinuria. The median age of the recipient was 39 years (interquartile range 28-47), where 77% were male and 5.5% had been previously transplanted and 84% of donors were unrelated. Histological diagnosis was as follow; acute T-cell mediated rejection (A-TCMR; 23.1%), acute tubular necrosis (ATN; 14.8%), interstitial fibrosis and tubular atrophy (IFTA; 11.4%), recurrent or de novo kidney disease (R/DKD; 8.6%), transplant glomerulopathy (TG; 7.6%), calcineurin inhibitor toxicity (CNI; 6.9%), and active antibody-mediated rejection (A-AMR; 8.6%). Early graft dysfunctions were A-TCMR (29%) and ATN (22.4%). Late graft dysfunction included IF/TA, (20.2%), TG (20.2%), R/DRD (17%), and A-TCMR (9.5%). C4d+AMR was equally represented in early (5.6%) and late (6.3%) biopsies. Conclusion: A-TCMR was the most common cause of early graft dysfunction and was replaced by chronic conditions as the cause of 57.8% of late graft biopsies. The causes of graft dysfunction are not remarkably different from the west and TG will be a major cause of late graft failure in Iraq.

The Summarized Assessment of Endothelin A Receptor Expression in Renal Transplant Compartments Associated with Antibody-Mediated Rejection.

The occurrence of anti-endothelin A receptor antibodies may be useful in diagnosis of transplant damage. We noticed that the presence of the endothelin A receptor (ETA receptor) in biopsy compartments is yet to be defined. We decided therefore to analysed the presence and relevance of the ETA receptor in biopsy to define the cause. Our study aims to evaluate the expression of ETA receptors in renal recipients after a biopsy due to the worsening of transplant function. Methods: The expression of ETA receptors was analyzed in renal transplant biopsies using the immunohistochemical method. The evaluation of ETA receptors was performed on paraffin sections. ETA receptor expression was analyzed in four compartments of renal transplant biopsies: glomeruli; vessels; tubular epithelium; and interstitium. The assessment was presented using a three-step scale (0: lack of expression; 1: mild to moderate immunoreactivity; 2: high expression). The results of each compartment from a single biopsy were summarized and assessed in the context of antibody-mediated rejection (AMR). Results: We analyzed 156 patients who had a renal allograft biopsy after renal transplantation. For each patient, we created a summarized ETA receptor expression score. The summarized ETA receptor expression score analysis showed statistically significant differences in patients with and without AMR. In addition, we noticed that patients with AMR had a significantly higher mean summarized expression of ETA receptor score of 3.28 ± 1.56 compared to patients who had a biopsy for other reasons with a mean summarized ETA receptor expression score of 1.47 ± 1.35 (p < 0.000001). ROC analysis of the ETA receptor expression score for detecting AMR status showed that the most appropriate cut-off for the test of the chosen binary classifier is between 2 and 3 of the summarized ETA receptor expression score. Conclusions: The expression of endothelin A receptors in renal transplant compartments may be associated with antibody-mediated rejection. The positive ETA receptor staining might be a vital feature in the diagnosis of damage in AMR. The summarized ETA receptor expression score seems to be an exciting diagnostic tool in transplant injury assessment.

Donor-Specific Antibody Is Associated with Increased Expression of Rejection Transcripts in Renal Transplant Biopsies Classified as No Rejection.

Donor -specific HLA antibody (DSA) is present in many kidney transplant patients whose biopsies are classified as no rejection (NR). We explored whether in some NR kidneys DSA has subtle effects not currently being recognized. We used microarrays to examine the relationship between standard-of-care DSA and rejection-related transcript increases in 1679 kidney transplant indication biopsies in the INTERCOMEX study (ClinicalTrials.gov NCT01299168), focusing on biopsies classified as NR by automatically assigned archetypal clustering. DSA testing results were available for 835 NR biopsies and were positive in 271 (32%). DSA positivity in NR biopsies was associated with mildly increased expression of antibody-mediated rejection (ABMR)-related transcripts, particularly IFNG-inducible and NK cell transcripts. We developed a machine learning DSA probability (DSAProb) classifier based on transcript expression in biopsies from DSA-positive versus DSA-negative patients, assigning scores using 10-fold cross-validation. This DSAProb classifier was very similar to a previously described "ABMR probability" classifier trained on histologic ABMR in transcript associations and prediction of molecular or histologic ABMR. Plotting the biopsies using Uniform Manifold Approximation and Projection revealed a gradient of increasing molecular ABMR-like transcript expression in NR biopsies, associated with increased DSA (P<2 × 10-16). In biopsies with no molecular or histologic rejection, increased DSAProb or ABMR probability scores were associated with increased risk of kidney failure over 3 years. Many biopsies currently considered to have no molecular or histologic rejection have mild increases in expression of ABMR-related transcripts, associated with increasing frequency of DSA. Thus, mild molecular ABMR-related pathology is more common than previously realized.