Early Protocol Biopsies Research Articles

Antibody-mediated rejection diagnosed in early protocol biopsies in high immunological risk kidney transplant recipients.

Renal transplant recipients with donor-specific anti-HLA antibodies are at an increased risk of antibody-mediated rejection (AMR). Early protocolized renal biopsies may serve as a strategy to improve diagnosis in this patient population. We evaluated 155 highly sensitized renal transplant recipients with cPRA class I+II>90% pre-transplant from 2015 to 2022. Patients with protocol biopsies within the first two weeks post-transplant were included. A total of 122 patients were included in the study. Of these, 13 (10.6%) were diagnosed with very early antibody-mediated rejection (veABMR) within the first two weeks post-transplant. This corresponds to 52% (13/25 patients) of all ABMR cases reported during the follow-up of this population. The graft survival rates at one and three years were significantly lower in patients with veABMR (p<0.001) compared to patients without rejection in the early protocol biopsy. In terms of severity, the veABMR cohort exhibited a hazard ratio (HR) of 10.33 (95% CI 3.23-33.06; p<0.001) for graft failure. The presence of donor-specific antibodies (DSA) class II on the day of transplantation and a higher percentage of eplet mismatch (EpMM), particularly EpMM DQA1, correlated with the development of veABMR. Early protocol biopsies play a pivotal role in the early detection of veABMR in high-risk immunological patients. Patients with veABMR face significant risks of graft loss, despite early treatment of rejection.

#2504 Histopathological findings and cardiovascular events in kidney transplantation

Abstract Background and Aims Despite offering superior outcomes for patients with end-stage kidney disease, kidney transplantation poses significant cardiovascular risks. Recently, histopathological findings in chronic kidney disease patients have been associated with all-cause mortality and cardiovascular events, but there is scant data on this subject in kidney transplant recipients. This study assesses the relationship between histopathological findings in protocol biopsies of kidney grafts and cardiovascular events, graft loss, and mortality in renal transplant recipients. Method A prospective observational study included 530 renal transplant recipients at the Hospital Clínic de Barcelona from March 2015 to 2019, with follow-up until March 2023. Data included demographics, comorbidities, laboratory tests, and protocol allograft biopsies at 3 and 12 months post-transplant. Associations between histopathological findings and outcomes (cardiovascular events, graft loss, mortality) were analyzed. Results Chronic vascular lesions (CV) were significantly correlated with cardiovascular death and major adverse cardiovascular events (MACE) (OR 10.4 (1.6–66.4); p 0.002). Arteriolar hyalinosis and interstitial fibrosis were independently associated with all-cause mortality (OR 4.9 (1.1-21.4); p 0.02, and 1.2 (1.03-1.3), p 0.005; respectively) regardless of the estimated glomerular filtration rate (eGFR). Associations were also found between pre-transplant factors (diabetes, hypertension, hyperphosphatemia), active smoking, and deceased donors. Notably, post-transplant hypophosphatemia was related to MACE, suggesting a potential association with malnutrition though, this subject requires further investigation. Conclusion Histopathological findings in early protocol biopsies of kidney grafts, especially chronic vascular lesions, arteriolar hyalinosis, and interstitial fibrosis, have a potential predictive value for cardiovascular events, mortality, and graft outcomes in transplant recipients, irrespective of eGFR. These insights emphasize the importance of timely post-transplant histological assessments for risk stratification and personalized interventions. Prospective studies are imperative to validate these findings and improve customized care strategies in this population.

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.

Evaluation of serial monitoring of donor-specific antibodies in pediatric and adult intestinal/multivisceral transplant recipients.

The study purpose was to add to limited literature assessing anti-HLA donor-specific antibody (DSA) appearance, clearance, specificity, and impact in intestinal/multivisceral (MV) transplant as well as the value of serial monitoring following an institutional protocol shift implementing serial monitoring. This single-center retrospective review included intestinal/MV recipients transplanted 1/1/15-9/31/17 with completed DSA testing. Patients were divided into groups based on DSA presence post-transplant. The primary outcome was biopsy-proven acute rejection (BPAR). Secondary outcomes included graft loss and death. Descriptive analysis of DSA was completed. Of the 35 intestinal/MV recipients (60% pediatric) with DSA testing, 24 patients had post-transplant DSA. Fifteen patients in the DSA(+) group had T-cell-mediated BPAR versus five in the DSA(-) group (63% vs 45%, p = .47). Days to BPAR were 25 [IQR 19-165] (DSA(+) group) versus 232 [IQR 25.5-632.5] (DSA(-) group) (p = .066). There were no differences between groups for graft loss or death. One hundred and five DSA were identified in the DSA(+) group with 63% being class II, and 54% cleared during follow-up. DSA were directed against 50 different HLA alleles, with the most common being directed against HLA- DQ (35%). Time to first DSA and to clearance did not differ between class I and II. Findings confirm previous data that suggest post-transplant DSA in this population may lead to increased BPAR or shorter time to BPAR, although not statistically significant. Most DSA were identified within the first month after transplant, and ahead of rejection identification on biopsy. DSA therefore may have utility as an early rejection biomarker and use may be considered in place of early protocol biopsies, particularly in pediatric patients. We identified novel findings of DSA directed against a large breadth of HLA in intestinal/MV patients.

Feasibility and safety of 2-week protocol biopsy after kidney transplantation

Background: Protocol biopsies to detect and treat subclinical rejection early after kidney transplantation are useful for improv ing outcomes. However, there have been few studies on the optimal timing of early protocol biopsy. In this study, the results of 2-week and 1-year biopsies were analyzed in terms of technical feasibility, complications, and outcomes. Methods: Allograft protocol biopsies were performed in 916 adult recipients of kidney transplantation between 2012 and 2019 in our center. Retrospective analysis of complications and clinical outcomes of 880 2-week biopsies and 556 1-year biopsies were performed. Results: There were no significant difference between the median number of biopsy cores and sampled glomeruli of 2-week biopsies and 1-year biopsies. All allograft biopsies were technically successful. Total complication rates of 2-week and 1-year biopsies were 27.5% (242/880) and 15.5% (86/556). Major complication (Clavien-Dindo grading III-IV) rates of 2-week and 1-year biopsies were 0.23% (2/880) and 0.18% (1/556). There were only two major complication cases in 2-week biopsies: bleeding requiring surgical exploration (n=1) and bleeding requiring radiological intervention (n=1), and was only one major complication case in 1-year biopsies: allograft failure (n=1). There was no significant risk factor for major complication, even though immuno logic factors, pre-biopsy laboratory results, basic characteristics are analyzed with univariate and multivariate analysis. Detection rates of subclinical rejection was 16.5% (145/880) for 2-week biopsies and 32.9% (183/556) for 1-year biopsies. Conclusions: The 2-week protocol biopsy is as feasible and safe as the 1-year protocol biopsy in kidney transplant. It contributes to early detection of a significant number of subclinical rejection after kidney transplantation.

Urinary Human Epididymis Secretory Protein 4 as a Useful Biomarker for Subclinical Acute Rejection Three Months after Kidney Transplantation.

Kidney transplantation is the treatment of choice for patients with advanced chronic kidney disease (CKD) and end stage renal disease (ESRD). However, acute rejection (AR) is a common complication in kidney transplantation and is associated with reduced graft survival. Current diagnosis of AR relies mainly on clinical monitoring including serum creatinine, proteinuria, and confirmation by histopathologic assessment in the biopsy specimen of graft kidney. Although an early protocol biopsy is indispensable for depicting the severity of pathologic lesions in subclinical acute rejection (subAR), it is not acceptable in some cases and cannot be performed because of its invasive nature. Therefore, we examined the detection of noninvasive biomarkers that are closely related to the pathology of subAR in protocol biopsies three months after kidney transplantation. In this study, the urinary level of microtubule-associated protein 1 light chain 3 (LC3), monocyte chemotactic protein-1 (MCP-1), liver-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL), and human epididymis secretory protein 4 (HE4) were measured three months after kidney transplantation. Urine samples of 80 patients undergoing kidney transplantation between August 2014 to September 2016, were prospectively collected after three months. SubAR was observed in 11 patients (13.8%) in protocol biopsy. The urinary levels of LC3, MCP-1, NGAL, and HE4 were significantly higher in patients with subAR than in those without, while those of L-FABP did not differ between the two groups. Multivariate regression models, receiver-operating characteristics (ROC), and areas under ROC curves (AUC) were used to identify predicted values of subAR. Urinary HE4 levels were able to better identify subAR (AUC = 0.808) than the other four urinary biomarkers. In conclusion, urinary HE4 is increased in kidney transplant recipients of subAR three months after kidney transplantation, suggesting that HE4 has the potential to be used as a novel clinical biomarker for predicting subAR.

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits is associated with high rate of early recurrence in the allograft

The characteristics of allograft proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID) are not well defined. To better characterize this disease we retrospectively identified 26 patients with allograft PGNMID, including 16 followed with early protocol biopsies. PGNMID was found to be a recurrent disease in most (89%) patients. A diagnostic biopsy was done for proteinuria and/or increased creatinine in most patients. Median time from transplant to diagnostic biopsy was 5.5 months, with detection within three to four months post-transplant in 86% of patients. Mesangial proliferative glomerulonephritis was the most common pattern on the diagnostic biopsy with 89% of cases showing immunoglobulin G3 subtype restriction. A detectable serum paraprotein was present in 20% of patients. During a mean follow up of 87 months from implantation, 11 of 25 patients lost their allograft largely due to PGNMID within a mean of 36 months from diagnosis. Median graft survival was 92 months. Independent predictors of graft loss were a higher degree of peak proteinuria and longer time from implantation to diagnosis. Sixteen patients were treated with immunosuppressive therapy which resulted in over 50% reduction in proteinuria in 60%, and improvement of glomerular pathology in nine of 13 patients. However, 44% of responders subsequently relapsed. Thus, PGNMID has a high recurrence rate in renal allografts occurring early with detection enhanced by protocol biopsies. Graft outcome is guarded as nearly half of patients lose their graft within three years from diagnosis. Hence, there is a need for better treatment strategies for this disease.

Utility of Serial Protocol Biopsies Performed After 1 Year in Predicting Long-Term Kidney Allograft Function According to Histologic Phenotype.

Prognostic implications of early protocol biopsies have been studied; however, the value of late protocol biopsy in predicting graft outcome has not been well defined. Here, we compared the effects of early and late protocol biopsy histologic findings in stable kidney allografts and aimed to understand the significance of "borderline" rejection on allograft function. We studied 261 biopsies from 159 renal transplant recipients who were on a steroid-free, calcineurin inhibitor and mycophenolate mofetil regimen and who received transplants between 2004 and 2012 with mean follow-up of 5 years. Early (between 3 and 9 mo) and subsequent late (between 12 and 24 mo) protocol biopsies were performed. Biopsies were classified as normal, interstitial fibrosis and/or tubular atrophy, subclinical acute rejection with interstitial fibrosis and/or tubular atrophy, and borderline rejection with interstitial fibrosis and/or tubular atrophy. A linear mixed-effects model was used to determine the effects of early and late protocol biopsies on estimated glomerular filtration rate changes, with baseline time for estimated glomerular filtration rate fixed at 12 months. The adjusted model showed that estimated glomerular filtration rate at 3 months, donor age, delayed graft function, and early protocol biopsies were associated with baseline estimated glomerular filtration rate at 12 months. Estimated glomerular filtration rate changes over time were associated with findings of interstitial fibrosis and/or tubular atrophy at early biopsy and subclinical acute rejection and borderline rejection at late biopsy. At last follow-up, final estimated glomerular filtration rate was significantly associated with interstitial fibrosis and/or tubular atrophy at early biopsy and with subclinical acute rejection at late biopsy. Although early protocol biopsy predicted baseline estimated glomerular filtration rate, late biopsy was important for predicting changes in function over time. In addition, a diagnosis of "borderline" rejection on protocol biopsies predicted long-term graft function.

Molecular diagnostics identifies risks for graft dysfunction despite borderline histologic changes

The significance of borderline changes in kidney allograft biopsies is widely debated. To help resolve this, we studied differences in intrarenal gene expression patterns between early clinical and 3-month protocol biopsies, all of which had borderline histologic changes. The gene expression profiles in training set of patients by microarray analysis and data were validated in a larger cohort using RT-qPCR. There was greater expression of immunity- and inflammation-related genes in the early clinical biopsies compared to the 3-month protocol biopsies with borderline changes. In early clinically manifested borderline changes, graft deterioration within 24 months due to chronic rejection was associated with increased activation of immune, defense, and inflammatory processes. Regression modeling identified higher donor age and expression of macrophage receptor CLEC5A as risk factors for progression. In the 3-month protocol biopsies with borderline changes, graft dysfunction was associated with increased expression of fibrinogen complex transcripts. The discrimination power of fibrinogen was confirmed by cross-validation on two independent cohorts. Thus, our study highlights variations in gene expression between clinical and subclinical borderline changes despite similar histological findings. The data also support a recommendation for frequent patient monitoring, especially in those with borderline changes who received grafts from older donors.

Microvascular inflammation in early protocol biopsies of renal allografts in cases of chronic active antibody-mediated rejection.

Chronic active antibody-mediated rejection (chronic ABMR) is one important cause of late-stage renal allograft loss. However, few reports have used protocol biopsy to observe changes over time in cases that develop chronic ABMR. The aim of this study was to use protocol biopsy to clarify the histological features of cases that develop chronic ABMR. We recruited 379 ABO compatible patients who underwent protocol biopsy at our hospital from 2010 to 2014. Seventeen of these patients were diagnosed with chronic ABMR (chronic ABMR group), and 12 patients were class 2 donor-specific antibody (DSA) positive and were not diagnosed with chronic ABMR (class 2 DSA-positive group). With the addition of a control group consisting of 30 DSA negative patients, these three groups were compared for Banff factors in protocol biopsies taken 3 months, 6 months, 1 year, 3 years, and 5 years after the transplant. Three months post transplant, the chronic ABMR group had a significantly higher number of patients exhibiting g + ptc > 0 than that in the control group (P = 0.01). At 1, 3, and 5 years post transplant, significantly more subjects in the chronic ABMR and class 2 DSA-positive groups compared with the control group exhibited g + ptc > 0 (P < 0.03). Five years post transplant, the chronic ABMR group exhibited a significantly higher mean c4d score than that in the control group (P = 0.02). The only significant difference observed between the chronic ABMR group and the class 2 DSA-positive group was in cg scores at 5 years post transplant, which were significantly higher in the chronic ABMR group (P = 0.03). These results suggest that cases exhibiting microvascular inflammation in the early post-transplant period may develop chronic ABMR, and it would be highly beneficial to perform focused electron microscope surveillance of these cases.

Early subclinical rejection treated with low dose i.v. steroids is not associated to graft survival impairment: 13-years' experience at a single center.

Subclinical rejection (SCR) has been variably associated with reduced graft survival, development and progression of interstitial fibrosis/tubular atrophy and chronic allograft nephropathy, but data are controversial concerning SCR treatment in terms of graft survival improvement. In this single-center retrospective study, we enrolled 174 adult kidney transplant recipients with a protocol biopsy performed at 30days after transplantation to evaluate the incidence rate and risk factors for early SCR and its impact on 10-year graft survival. Five patients showed primary non function and were excluded. Among 159/169 (94.08%) patients with stable graft function who underwent protocol biopsy, 17 (10.7%) showed signs of SCR and were treated with low-dose intravenous (i.v.) steroids. Ten patients showed functional impairment, 8 (4.73%) resulting as acute rejection. At multivariate analysis, donor age [odds ratio (OR) 1.04, 95% confidence interval (CI) 1.01-1.09], and delayed graft function (DGF) (OR 1.08, 95% CI 1.03-1.12) were significantly associated with SCR. The 10-year graft survival rate in the SCR group was similar to that in the normal-findings group (76.5 vs. 74.9% respectively; p=0.61). At multivariate Cox regression, acute [hazard ratio (HR) 5.22, 95% CI 1.70-16.01], but not sub-clinical, rejection was independently associated with long-term graft failure. In conclusion, early protocol biopsy is a useful and safe tool to detect early SCR which seems not to affect the long-term survival. We suggest that this could be, probably, linked to early SCR treatment with low dose i.v. steroids.

Response-Guided Therapy for Hepatitis C Virus Recurrence Based on Early Protocol Biopsy after Liver Transplantation.

Hepatitis C virus (HCV) recurrence after liver transplantation (LT) is universal and progressive. Here, we report recent results of response-guided therapy for HCV recurrence based on early protocol biopsy after LT. We reviewed patients who underwent LT for HCV related liver disease between 2010 and 2012. Protocol biopsies were performed at 3, 6, and 12 months after LT in HCV recurrence (positive HCV-RNA). For any degree of fibrosis, ≥ moderate inflammation on histology or HCV hepatitis accompanying with abnormal liver function, we treated with pegylated interferon and ribavirin. We adjusted treatment period according to individual response to treatment. Among 41 HCV related recipients, 25 (61.0%) who underwent protocol biopsies more than once were enrolled in this study. The mean follow-up time was 43.1 (range, 23-55) months after LT. Genotype 1 and 2 showed in 56.0% and 36.0% patients, respectively. Of the 25 patients, 20 (80.0%) started HCV treatment after LT. Rapid or early virological response was observed in 20 (100%) patients. Fifteen (75.0%) patients finished the treatment with end-of-treatment response. Sustained virological response (SVR) was in 11 (55.0%) patients, including 5 (41.7%) of 12 genotype 1 and 6 (75.0%) of 8 non-genotype 1 (P = 0.197). Only rapid or complete early virological response was a significant predictor for HCV treatment response after LT (100% in SVR group vs. 55.6% in non-SVR group, P = 0.026). Overall 3-yr survival rate was 100%. In conclusion, response-guided therapy for HCV recurrence based on early protocol biopsy after LT shows encouraging results.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

Antibody-mediated rejection: analyzing the risk, proposing solutions.

The Impact of Late Surveillance Biopsy and Importance of “Borderline Rejection” On Allograft Outcome in Kidney Transplant Recipients.

Background: Our aim was to examine the impact of early and late surveillance biopsy findings on kidney allograft functional outcome. Many inflamed biopsies with changes insufficient to be called T-Cell-mediated rejection are labeled “borderline “and its implication on graft outcome remains uncertain. Methods: We studied 158 renal transplant recipients between 2004 to 2012; mean follow up was 5.2 (standard deviation: 0.24) yrs. Early protocol biopsy (B1) and late protocol biopsy (B2) were performed between 3-12 and 13-24 months (m) respectively. There were 102 patients who had both biopsies. Biopsies were classified as: interstitial fibrosis and/or tubular atrophy only (IFTA), normal histology (NML), acute rejection (AR), borderline rejection (BDR). Baseline graft function by estimated glomerular filtration rate (eGFR) was fixed at 12m while changes were evaluated up to last follow up eGFR. Univariate and multivariable linear mixed effect models were developed to examine the effects of surveillance biopsies on changes in the eGFR. Random intercepts and random time effects were considered in linear mixed model analysis. All statistical analyses were carried out using SAS 9.3. Results: The eGFR rate declined from 12m to last visit was found to be -1.26 ± 0.40(standard error) per year. Multivariate analysis revealed that eGFR at 3 m, donor age, and delayed graft function were associated with baseline eGFR while B1 and B2 findings were significantly associated with both baseline eGFR and change in eGFR over time. Final multivariate analysis of both B1 and B2 taken together showed that the change in eGFR was found to be associated with findings of IFTA in B1 (p=0.0038), AR in B2 (p=0.0605) and BDR in B2 (p=0.049) when compared to NML. All three abnormal histology groups had lower eGFR (AR=25.65 ±14.28 ml/min; p=0.1029), (BDR=42.17±19.24; p=0.016), (IFTA 45.26±16.13; p=0.016), than those with (NML=51.77±16.96 ml/min) at last follow up (p<0.05). Conclusion: Early biopsy results correlate with baseline GFR at 12m; while abnormal late surveillance biopsy results significantly impact GFR decline over long-term. In addition, the diagnosis of borderline inflammation on surveillance biopsy affected graft functional status on long-term follow up.

Early protocol biopsies in pediatric renal transplantation: Interest for the adaptation of immunosuppression

GPB are often performed in PRT to detect subclinical acute rejection or IF/TA. Reducing immunosuppression side effects without increasing rejection is a major concern in PRT. We report the results of GPB in children transplanted with a steroid-sparing protocol adapted to immunological risk. Children under 18 yr who received a renal transplantation between April 1, 2009 and May 31, 2012 were included. Immunosuppression consisted of an antibody induction therapy, tacrolimus, and MMF for all recipients. CSs were administered to children under five yr old, or receiving a second allograft. Twenty-eight children were included, 50% were CSs free. GPB were performed between three and six months. IF/TA was documented in seven biopsies; four of these seven children were CS free. One child, with CSs, presented a borderline rejection, and another child, steroid free, with significant inflammatory interstitial infiltrate, considered as a subclinical rejection, was treated with CSs pulses. The median eGFR was stable (74, 67.5, and 82 mL/min/1.73 m² at, respectively, seven days, three months, and one yr). Patient and graft survival were 100%. These results have to be confirmed in a larger cohort, with long-term follow-up.

Kidney graft dysfunction in simultaneous pancreas–kidney recipients after pancreas failure: analysis of early and late protocol biopsies

Kidney graft survival in simultaneous pancreas-kidney (SPK) recipients is known to decrease after pancreas graft failure. Sixty-three consecutive SPK recipients were retrospectively reviewed. Kidney graft function and proteinuria were evaluated at three months after the transplantation and at last follow-up. Histopathologic findings of protocol biopsies performed three months and one yr after transplantation were analyzed. Twelve patients lost the pancreas graft. Donors' characteristics were similar in patients with or without pancreas failure. After a median follow-up of 36months, mean eGFR with a functional pancreas was 69.5mL/min/1.73m² vs. 56.3mL/min/1.73m² (p=0.01) after pancreas loss. Patients who lost pancreas had a median proteinuria of 0.28g vs. 0.13g per 24h (p=0.02). Analysis of three-month protocol biopsies revealed more frequent isolated glomerulitis after pancreas failure (p=0.0001), without peritubular capillaritis or C4d deposition. No donor-specific anti-HLA antibodies were detectable in these patients. Chronic tubulointerstitial changes were more frequent in patients with pancreas loss. There was no evidence of diabetic nephropathy recurrence. SPK recipients develop an early kidney graft dysfunction after pancreas failure. Histopathologic findings revealed frequent glomerulitis without antibody-mediated rejection and early chronic changes.

Long‐term histopathology of allografts in sensitized kidney recipients

Successful desensitization therapy has brought satisfying short-term outcomes in the recipients with anti-donor antibody. We analyzed the long-term pathology of the allografts in the sensitized kidney recipients. Eleven stable recipients after desensitization against positive flow cytometry T-cell crossmatch (FTXM) were included. They were divided into two groups, based on the protocol biopsies findings at three to eight yr (group 1: subclinical glomerulitis and/or peritubular capillaritis, n = 5 and group 2: no rejection, n = 6). Estimated glomerular filtration rate (eGFR), presence of donor-specific antibody (DSA), mean channel shift (MCS) of FTXM, urine protein levels, acute antibody-mediated rejection (AAMR) episodes, and protocol biopsy findings were compared. Chronic transplant glomerulopathy was found in final biopsy of all group 1 cases. DSA was positive in 60% but C4d was positive in 20% case of the group 1. The history of AAMR was only found in the group 1. There was no difference in eGFR decline or proteinuria. The MCS of FTXM was higher in the group 1. The recipients with AAMR history, high MCS in FTXM, and subclinical microvascular inflammation in the early protocol biopsies have risk for developing chronic rejection in long term.

Early Subclinical Rejection as a Risk Factor for Late Chronic Humoral Rejection

Subclinical rejection and interstitial fibrosis and tubular atrophy (IF/TA) in protocol biopsies are associated with outcome. We study the relationship between histologic lesions in early protocol biopsies and histologic diagnoses in late biopsies for cause. Renal transplants with a protocol biopsy performed within the first 6 months posttransplant between 1988 and 2006 were reviewed. Biopsies were evaluated according to Banff criteria, and C4d staining was available in biopsies for cause. Of the 517 renal transplants with a protocol biopsy, 109 had a subsequent biopsy for cause which showed the following histological diagnoses: chronic humoral rejection (CHR) (n=44), IF/TA (n=42), recurrence of the primary disease (n=11), de novo glomerulonephritis (n=7), T-cell-mediated rejection (n=4), and polyoma virus nephropathy (n=1). The proportion of retransplants (15.9% vs. 2.3%, P=0.058) and the prevalence of subclinical rejection were higher in patients with CHR than in patients with IF/TA (52.3% vs. 28.6%, P=0.0253). Demographic donor and recipient characteristics and clinical data at the time of protocol biopsy were not different between groups. Logistic regression analysis showed that subclinical rejection (relative risk, 2.52; 95% confidence interval, 1.1-6.3; P=0.047) but not retransplantation (relative risk, 6.7; 95% confidence interval, 0.8-58.8; P=0.085) was associated with CHR. Subclinical rejection in early protocol biopsies is associated with late appearance of CHR.

The Molecular Phenotype of 6-Week Protocol Biopsies from Human Renal Allografts: Reflections of Prior Injury but Not Future Course

We assessed the molecular phenotype of 107 6-week protocol biopsies from human renal allografts, using Affymetrix microarrays. Transcript changes were summarized as nonoverlapping pathogenesis-based transcript sets (PBTs) reflecting inflammation (T cells, macrophages, IFNG effects) and the injury-repair response of the parenchyma, stroma and microcirculation-increased ('injury-up') and decreased ('injury-down') transcripts. The molecular changes were highly correlated with each other, even when all rejection and borderline cases were excluded. Inflammation and injury-down PBTs correlated with histologic inflammation and tubulitis, and the inflammation transcripts were greater in kidneys diagnosed as T cell-mediated or borderline rejection. Injury-up PBTs did not correlate with histopathology but did correlate with kidney function: thus functional disturbances are represented in transcript changes but not in histopathology. PBT changes correlated with prior delayed graft function. However, there was little difference between live donor kidneys and deceased donor kidneys that had not shown delayed graft function. Molecular changes did not predict future biopsies for clinical indications, rejection episodes, functional deterioration or allograft loss. Thus while detecting T cell-mediated inflammation, the molecular phenotype of early protocol biopsies mostly reflects the injury-repair response to implantation stresses, and has little relationship to future events and outcomes.

Significance of C4d Banff Scores in Early Protocol Biopsies of Kidney Transplant Recipients with Preformed Donor-Specific Antibodies (DSA)

The significance of C4d-Banff scores in protocol biopsies of kidney transplant recipients with preformed donor-specific antibodies (DSA) has not been determined. We reviewed 157 protocol biopsies from 80 DSA+ patients obtained at 3 months and 1 year post-transplant. The C4d Banff scores (1,2,3) were associated with significant increments of microcirculation inflammation (MI) at both 3 months and 1 year post-transplant, worse transplant glomerulopathy and higher class II DSA-MFI (p < 0.01). Minimal-C4d had injury intermediate between negative and focal, while focal and diffuse-C4d had the same degree of microvascular injury. A total of 54% of patients had variation of C4d score between 3 months and 1 year post-transplant. Cumulative (3 month + 1 year) C4d scores correlated with long-term renal function worsening (p = 0.006). However, C4d staining was not a sensitive indicator of parenchymal disease, 55% of C4d-negative biopsies having evidence of concomitant MI. Multivariate analysis demonstrated that the presence of MI and class II DSA at 3 months were associated with a fourfold increased risk of progression to chronic antibody-mediated rejection independently of C4d (p < 0.05). In conclusion, the substantial fluctuation of C4d status in the first year post-transplant reflects a dynamic humoral process. However, C4d may not be a sufficiently sensitive indicator of activity, MI and DSA being more robust predictors of bad outcome.