International standardization of criteria for the histologic diagnosis of renal allograft rejection: the Banff working classification of kidney transplant pathology

Distinct morphological features of acute tubular injury in renal allografts correlate with clinical outcome

Acute tubular injury (ATI) is common in renal allografts and is related to inferior long-term allograft function. However, it is unknown which of the morphological features of ATI can predict outcome and how they should be graded. Here, we examine features of ATI systematically in protocol biopsies and biopsies for cause to define the most predictive features. Analyses included 521 protocol biopsies taken at 6 wk, 3 mo, and 6 mo after transplantation and 141 biopsies for cause from 204 patients. Features of ATI included brush border loss, tubular epithelial lucency, flattening, pyknosis, nuclei loss, and luminal debris, each graded semiquantitatively. Additional immunohistochemical stainings were performed for markers of cell injury (neutrophil gelatinase-associated lipocalin), cell death [cleaved caspase-3, fatty acid-coenzyme A ligase 4 (FACL4)], and proliferation (K_i-67). Interobserver reliability was good for pyknosis, flattening, and brush border loss and poor for lucency, nuclei loss, and luminal debris. In protocol biopsies between 6 wk and 6 mo, the degree of ATI remained virtually unchanged. Biopsies for cause had generally higher injury scores. Deceased donor source, delayed graft function, ganciclovir/valganciclovir treatment, and urinary tract infection correlated with ATI. The degree of pyknosis, flattening, and brush border loss correlated best with impaired allograft function. FACL4 expression was observed in areas of ATI. Only patients with K_i-67 expression showed stable or improved allograft function in the longitudinal assessment. Reliable assessment of ATI is possible by semiquantitative grading of tubular epithelial cell brush border loss, flattening, and pyknosis. Examination of K_i-67 expression can help determine the potential for recovery from this damage.

Isolated v-lesion in kidney transplant recipients: Characteristics, association with DSA, and histological follow-up

Isolated v-lesion (IvL) represents a rare and challenging situation in renal allograft biopsies because it is unknown whether IvL truly represents rejection, antibody- or T cell-mediated, or not. This multicentric retrospective study describes the clinicopathological features of IvL with an emphasis on the donor-specific antibody (DSA) status, histological follow-up, and graft survival. Inclusion criteria were the presence of v-lesion with minimal interstitial (i ≤ 1) and microvascular inflammation (g + ptc≤1). C4d-positive biopsies were excluded. We retrospectively found 33 IvL biopsies in 33 patients, mainly performed in the early posttransplantation period (median time 27 days) and clinically indicated in 66.7%. A minority of recipients (5/33, 15.2%) had DSA at the time of biopsy. IvL was treated by anti-rejection therapy in 21 cases (63.6%), whereas 12 (36.4%) were untreated. Seventy percent of untreated patients and 66% of treated patients showed favorable histological evolution on subsequent biopsy. Kidney graft survival in IvL was significantly higher than in a matched cohort of antibody-mediated rejection with arteritis. In conclusion, IvL is not primarily antibody-mediated and may show a favorable evolution. The heterogeneity of IvL pathophysiology on early biopsies should prompt DSA testing as well as close clinical and histological follow-up in all patients with IvL.

[The pathology of renal transplants]

In order to make an objective assessment of the histopathology of a renal biopsy during a kidney transplant, all the various elements involved in the process must be understood. It is important to know the characteristics of the donor organ, especially if the donor is older than 65. The histopathological features of the donor biopsy, especially its vascular status, are often related to an initial poor function of the transplanted kidney. The T lymphocyte inflammatory response is characteristic in acute cellular rejection; the degree of tubulitis, together with the amount of affected parenchyme, are important factors. The proportion of cellular sub-populations, such as plasma cells and macrophages, is also important, as they can be related to antibody-mediated humoral rejection. Immunofluorescent or immunohistochemical studies are necessary to rule out C4d deposits or immunogloblulins. The presence of abundant deposits of C4d in tubular basement membranes supports a diagnosis of humoral rejection, as does the presence of capillaritis, glomerulitis which, together with vasculitis, are typical diagnostic findings in C4d negative cases. Interstitial fibrosis, tubular atrophy and glomerular sclerosis, although non-specific, imply a chronic phase. Transplant glomerulopathy and multilamination in more than 6 layers of the tubular and glomerular basement membranes are quasi-specific characteristics of chronic humoral rejection. Electron microscopy is essential to identify of these pathologies as well as to demonstrate the presence of other glomerular renal diseases.

A Humanized Mouse Model Generated Using Surplus Neonatal Tissue

Here, we describe the NeoThy humanized mouse model created using non-fetal human tissue sources, cryopreserved neonatal thymus and umbilical cord blood hematopoietic stem cells (HSCs). Conventional humanized mouse models are made by engrafting human fetal thymus and HSCs into immunocompromised mice. These mice harbor functional human T cells that have matured in the presence of human self-peptides and human leukocyte antigen molecules. Neonatal thymus tissue is more abundant and developmentally mature and allows for creation of up to ∼50-fold more mice per donor compared with fetal tissue models. The NeoThy has equivalent frequencies of engrafted human immune cells compared with fetal tissue humanized mice and exhibits T cell function in assays of ex vivo cell proliferation, interferon γ secretion, and in vivo graft infiltration. The NeoThy model may provide significant advantages for induced pluripotent stem cell immunogenicity studies, while bypassing the requirement for fetal tissue.

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Neonatal tissue is a viable alternative to fetal for mouse humanization

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Over 1,000 NeoThy mice can be made from one neonatal thymus donor

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The NeoThy enables robust pre-clinical immunogenicity studies of iPSC therapies

Proceedings of the 2nd BEAT-PCD conference and 3rd PCD training school: part 1

Primary ciliary dyskinesia (PCD) is a rare heterogenous condition that causes progressive suppurative lung disease, chronic rhinosinusitis, chronic otitis media, infertility and abnormal situs. 'Better Experimental Approaches to Treat Primary Ciliary Dyskinesia' (BEAT-PCD) is a network of scientists and clinicians coordinating research from basic science through to clinical care with the intention of developing treatments and diagnostics that lead to improved long-term outcomes for patients. BEAT-PCD activities are supported by EU funded COST Action (BM1407). The second BEAT-PCD conference, and third PCD training school were held jointly in April 2017 in Valencia, Spain. Presentations and workshops focussed on advancing the knowledge and skills relating to PCD in: basic science, epidemiology, diagnostic testing, clinical management and clinical trials. The multidisciplinary conference provided an interactive platform for exchanging ideas through a program of lectures, poster presentations, breakout sessions and workshops. Three working groups met to plan consensus statements. Progress with BEAT-PCD projects was shared and new collaborations were fostered. In this report, we summarize the meeting, highlighting developments made during the meeting.

Polyomavirus BK Nephropathy-Associated Transcriptomic Signatures: A Critical Reevaluation

Background

Recent work using DNA microarrays has suggested that genes related to DNA replication, RNA polymerase assembly, and pathogen recognition receptors can serve as surrogate tissue biomarkers for polyomavirus BK nephropathy (BKPyVN).

Methods

We have examined this premise by looking for differential regulation of these genes using a different technology platform (RNA-seq) and an independent set 25 biopsies covering a wide spectrum of diagnoses.

Results

RNA-seq could discriminate T cell–mediated rejection from other common lesions seen in formalin fixed biopsy material. However, overlapping RNA-seq signatures were found among all disease processes investigated. Specifically, genes previously reported as being specific for the diagnosis of BKPyVN were found to be significantly upregulated in T cell–mediated rejection, inflamed areas of fibrosis/tubular atrophy, as well as acute tubular injury.

Conclusions

In conclusion, the search for virus specific molecular signatures is confounded by substantial overlap in pathogenetic mechanisms between BKPyVN and nonviral forms of allograft injury. Clinical heterogeneity, overlapping exposures, and different morphologic patterns and stage of disease are a source of substantial variability in “Omics” experiments. These variables should be better controlled in future biomarker studies on BKPyVN, T cell–mediated rejection, and other forms of allograft injury, before widespread implementation of these tests in the transplant clinic.

The causes, significance and consequences of inflammatory fibrosis in kidney transplantation: The Banff i-IFTA lesion

Inflammation within areas of interstitial fibrosis and tubular atrophy (i-IFTA) is associated with adverse outcomes in kidney transplantation. We evaluated i-IFTA in 429 indication- and 2052 protocol-driven biopsy samples from a longitudinal cohort of 362 kidney-pancreas recipients to determine its prevalence, time course, and relationships with T cell-mediated rejection (TCMR), immunosuppression, and outcome. Sequential histology demonstrated that i-IFTA was preceded by cellular interstitial inflammation and followed by IF/TA. The prevalence and intensity of i-IFTA increased with developing chronic fibrosis and correlated with inflammation, tubulitis, and immunosuppression era (P < .001). Tacrolimus era-based immunosuppression was associated with reduced histologic inflammation in unscarred and scarred i-IFTA compartments, ameliorated progression of IF, and increased conversion to inactive IF/TA (compared with cyclosporine era, P < .001). Prior acute (including borderline) TCMR and subclinical TCMR were followed by greater 1-year i-IFTA, remaining predictive by multivariate analysis and independent of humoral markers. One-year i-IFTA was associated with accelerated IF/TA, arterial fibrointimal hyperplasia, and chronic glomerulopathy and with reduced renal function (P < .001 versus no i-IFTA). In summary, i-IFTA is the histologic consequence of active T cell-mediated alloimmunity, representing the interface between inflammation and tubular injury with fibrotic healing. Uncontrolled i-IFTA is associated with adverse structural and functional outcomes.

The bridge between transplantation and regenerative medicine: Beginning a new Banff classification of tissue engineering pathology

The science of regenerative medicine is arguably older than transplantation-the first major textbook was published in 1901-and a major regenerative medicine meeting took place in 1988, three years before the first Banff transplant pathology meeting. However, the subject of regenerative medicine/tissue engineering pathology has never received focused attention. Defining and classifying tissue engineering pathology is long overdue. In the next decades, the field of transplantation will enlarge at least tenfold, through a hybrid of tissue engineering combined with existing approaches to lessening the organ shortage. Gradually, transplantation pathologists will become tissue-(re-) engineering pathologists with enhanced skill sets to address concerns involving the use of bioengineered organs. We outline ways of categorizing abnormalities in tissue-engineered organs through traditional light microscopy or other modalities including biomarkers. We propose creating a new Banff classification of tissue engineering pathology to standardize and assess de novo bioengineered solid organs transplantable success in vivo. We recommend constructing a framework for a classification of tissue engineering pathology now with interdisciplinary consensus discussions to further develop and finalize the classification at future Banff Transplant Pathology meetings, in collaboration with the human cell atlas project. A possible nosology of pathologic abnormalities in tissue-engineered organs is suggested.

T cell-mediated rejection is a major determinant of inflammation in scarred areas in kidney allografts

Inflammation in fibrosis areas (i-IF/TA) of kidney allografts is associated with allograft loss; however, its diagnostic significance remains to be determined. We investigated the clinicohistologic phenotype and determinants of i-IF/TA in a prospective cohort of 1539 kidney recipients undergoing evaluation of i-IF/TA and tubulitis in atrophic tubules (t-IF/TA) on protocol allograft biopsies performed at 1 year posttransplantation. We considered donor, recipient, and transplant characteristics, immunosuppression, and histological diagnoses in 2260 indication biopsies performed within the first year posttransplantation. Nine hundred forty-six (61.5%) patients presented interstitial fibrosis/tubular atrophy (IF/TA Banff grade > 0) at 1 year posttransplant, among whom 394 (41.6%) showed i-IF/TA. i-IF/TA correlated with concurrent t-IF/TA (P < .001), interstitial inflammation (P < .001), tubulitis (P < .001), total inflammation (P < .001), peritubular capillaritis (P < .001), interstitial fibrosis (P < .001), and tubular atrophy (P = .02). The independent determinants of i-IF/TA were previous T cell-mediated rejection (TCMR) (P < .001), BK virus nephropathy (P = .007), steroid therapy (P = .039), calcineurin inhibitor therapy (P = .011), inosine-5'-monophosphate dehydrogenase inhibitor therapy (P = .011), HLA-B mismatches (P = .012), and HLA-DR mismatches (P = .044). TCMR patients with i-IF/TA on posttreatment biopsy (N = 83/136, 61.0%) exhibited accelerated progression of IF/TA over time (P = .01) and decreased 8-year allograft survival (70.8% vs 83.5%, P = .038) compared to those without posttreatment i-IF/TA. Our results support that i-IF/TA may represent a manifestation of chronic active TCMR.

Lorraine Racusen and Kim Solez Awarded the Gold Medal of the Catalan Transplant Society

In March 2017, a joint meeting between The Catalan Society of Transplantation and the Banff Foundation was held at the University of Barcelona. This was an opportunity for the Catalan Society of Transplantation to recognize the crucial contributions to transplant pathology made by Lorraine Racusen and Kim Solez, who created and actively contributed to the development of the International Banff Classification System. The ceremony of the Gold Medal took place on March 31 at the University of Barcelona; it consisted of a presentation of the contributions of Lorraine Racusen and Kim Solez to the development of transplant pathology. In this article, the presentation of these awardees with the Gold Medal of the Catalan Society of Transplantation is summarized.

Pediatric renal transplant biopsy with ultrasound guidance: the 'core' essentials

This review provides a comprehensive and practical approach to pediatric percutaneous renal transplant biopsies, highlighting techniques and strategies to optimize adequate sample yield and ensure patient safety. In children with end-stage renal disease, transplantation is the preferred choice of therapy, providing for overall lower long-term morbidity and mortality compared with dialysis. In the ongoing management of renal transplant patients, core tissue sampling via a percutaneous renal biopsy remains the gold standard when transplant dysfunction is suspected. Indications for renal transplant biopsy and techniques/tools for adequate sample yield are discussed. Strategies for common challenges such as poor visualization and renal transplant mobility are addressed. We discuss the clinical signs, techniques and imaging findings for common complications including hematomas, arteriovenous fistulas and pseudoaneurysms. Although the percutaneous renal transplant biopsy procedure is generally safe with rare complications, care must be taken to ensure major complications are promptly recognized and treated. Adequate tissue samples obtained via renal biopsy are imperative to promptly identify transplant rejection to provide valuable information for patient diagnosis, treatment and outcomes. Radiologist and nephrologist attention to proper ultrasound techniques and optimal biopsy tools are critical to ensure tissue adequacy and minimize complications.

Real Time Central Assessment of Kidney Transplant Indication Biopsies by Microarrays: The INTERCOMEX Study

The authors conducted a prospective trial to assess the feasibility of real time central molecular assessment of kidney transplant biopsy samples from 10 North American or European centers. Biopsy samples taken 1 day to 34 years posttransplantation were stabilized in RNAlater, sent via courier overnight at ambient temperature to the central laboratory, and processed (29 h workflow) using microarrays to assess T cell- and antibody-mediated rejection (TCMR and ABMR, respectively). Of 538 biopsy samples submitted, 519 (96%) were sufficient for microarray analysis (average length, 3 mm). Automated reports were generated without knowledge of histology and HLA antibody, with diagnoses assigned based on Molecular Microscope Diagnostic System (MMDx) classifier algorithms and signed out by one observer. Agreement between MMDx and histology (balanced accuracy) was 77% for TCMR, 77% for ABMR, and 76% for no rejection. A classification tree derived to provide automated sign-outs predicted the observer sign-outs with >90% accuracy. In 451 biopsy samples where feedback was obtained, clinicians indicated that MMDx more frequently agreed with clinical judgment (87%) than did histology (80%) (p = 0.0042). In 81% of feedback forms, clinicians reported that MMDx increased confidence in management compared with conventional assessment alone. The authors conclude that real time central molecular assessment is feasible and offers a useful new dimension in biopsy interpretation. ClinicalTrials.gov NCT#01299168.

Graft loss among renal-transplant recipients with early reduction of immunosuppression for BK viremia

AIM

To review the incidence of graft loss and acute rejection among renal transplant recipients with early reduction of immunosuppression for BK viremia.

METHODS

We performed a retrospective analysis of consecutive de-novo kidney-only transplants from January 2009 to December 2012 to evaluate the incidence of Polyoma-virus associated nephropathy (PyVAN). Recipient plasma was screened for BKV DNA via quantitative polymerase chain reaction (PCR) at months 1, 3, 6, 9 and 12 post-transplant and on worsening graft function. Immunosuppression was reduced at ≥ 3-log copies/mL. Those with viremia of ≥ 4-log copies/mL (presumptive PyVAN) underwent renal transplant biopsy. Presumptive PyVAN (PP) and definitive PyVAN (DP; biopsy-proven) were treated by immunosuppression reduction (IR) only.

RESULTS

Among 319 kidney transplant recipients, the median age was 53 years (range 19-83), 65.8% were male, and 58.9% were white. Biopsy-proven acute rejection was found in 18.5% within 0-168 wk. Death-censored graft loss occurred in 5.3% (n = 17) and graft loss attributable to PyVAN was 0.6% (n = 2). Forty-seven patients were diagnosed with PP (14.7%) and 18 (5.6%) with DP. Graft loss among participants with PyVAN (8.5%) and those without (4.8%) was not significantly different. Deceased donor kidney transplantation (OR = 2.3, 95%CI = 1.1-4.6) and AR (OR = 2.3, 95%CI = 1.2-4.7) were associated with PyVAN in the multivariate analysis. BK viremia between 3 and 4-log copies/mL occurred in 27 patients, all of whom underwent IR. Of these, 16 (59%) never developed PyVAN while 11 (41%) developed PyVAN (4 DP, 7 PP) within a range of 11-39 wk.

CONCLUSION

Instituting an early reduction of immunosuppression, in the absence of adjunctive antivirals, is effective at preventing PyVAN and may be associated with a lower incidence of graft-loss without a reciprocal increase in the incidence of acute rejection.

De novo immune complex deposition in kidney allografts: a series of 32 patients

Immune complex deposition in kidney allografts can include both recurrent and de novo processes. Recurrent glomerulonephritis is a well-recognized phenomenon and has been shown to be a common cause of allograft failure. De novo immune complex-mediated disease remains relatively poorly characterized, likely owing to the less frequent use of immunofluorescence and electron microscopy in the transplant setting. We performed a retrospective review of kidney allograft biopsies showing glomerular immune complex deposition. Cases with de novo deposits were identified and further organized into two groups depending on whether the immune complex deposition could be clinically and/or histologically classified. Thirty-two patients with de novo immune complex deposition were identified over a 7-year period. A broad range of immune complex-mediated injuries were observed, the majority (63%) of which could be readily classified either clinically or histologically. These included cases of membranous glomerulonephropathy, IgA nephropathy, infection-related glomerulonephritis and glomerulonephritis related to an underlying autoimmune process. A smaller subset of patients (37%) demonstrated immune complex deposition that was difficult to histologically or clinically classify. These patients typically showed mild mesangial immune complex deposition with co-dominant IgG and IgM staining by immunofluorescence microscopy. The presence of concurrent antibody-mediated rejection and donor-specific antibody positivity was significantly higher in the unclassifiable group. The significance of these deposits and their possible relationship to allograft rejection deserves further investigation.

Quantification of Interstitial Fibrosis in Renal Allografts and Clinical Correlates of Long-Term Graft Function

BACKGROUND

The present study investigated interstitial fibrosis (IF) in 144 kidney recipients 0 h and 1 year post transplantation and assessed relationships with Banff code scores, clinical parameters, and long-term graft function.

METHODS

A quantitative analysis of IF was performed using the computer-assisted imaging of Sirius red-stained biopsy samples. Percent IF (%IF) in the cortical region was assessed at 0 h and 1 year, and an increase in the ratio of %IF from 0 h to 1 year was calculated. The relationship between %IF and Banff code scores was analyzed. Demographics and trough concentrations of tacrolimus were tested as risk factors in the top 20 patients with increases in %IF. The influence of increases in the ratio of %IF at 1 year on long-term graft function and survival was also assessed in these 20 patients.

RESULTS

Median %IF at 0 h and 1 year were 1.55 and 2.80%, respectively. No correlation was found between %IF and Banff code scores. The mean increase in the ratio of %IF from 0 h to 1 year was 4.31-fold. The increase in %IF in the top 20 patients correlated with diabetes mellitus. Graft function, but not graft survival, was lower in the top 20 patients for 10 years post transplantation.

CONCLUSIONS

A correlation was not found between %IF and Banff code scores. Greater increases in %IF within 1 year post transplantation may influence long-term graft survival. Computer-analyzed increases in %IF at 1 year may be a surrogate marker for long-term graft function.

Defining the phenotype of antibody-mediated rejection in kidney transplantation: Advances in diagnosis of antibody injury

The diagnostic criteria for antibody-mediated rejection (ABMR) are constantly evolving in light of the evidence. Inclusion of C4d-negative ABMR has been one of the major advances in the Banff Classification in recent years. Currently Banff 2015 classification requires evidence of donor specific antibodies (DSA), interaction between DSA and the endothelium, and acute tissue injury (in the form of microvasculature injury (MVI); acute thrombotic microangiopathy; or acute tubular injury in the absence of other apparent cause). In this article we review not only the ABMR phenotypes acknowledged in the most recent Banff classification, but also the phenotypes related to novel pathogenic antibodies (non-HLA DSA, antibody isoforms and subclasses, complement-binding functionality) and molecular diagnostic tools (gene transcripts, metabolites, small proteins, cytokines, and donor-derived cell-free DNA). These novel tools are also being considered for the prognosis and monitoring of treatment response. We propose that improved classification of ABMR based on underlying pathogenic mechanisms and outcomes will be an important step in identifying patient-centered therapies to extend graft survival.

Polyclonal and monoclonal antibodies for treating acute rejection episodes in kidney transplant recipients

BACKGROUND

Registry data shows that the incidence of acute rejection has been steadily falling. Approximately 10% to 35% of kidney recipients will undergo treatment for at least one episode of acute rejection within the first post-transplant year. Treatment options include pulsed steroid therapy, the use of an antibody preparation, the alteration of background immunosuppression, or combinations of these options. Over recent years, new treatment strategies have evolved, and in many parts of the world there has been an increase in use of tacrolimus and mycophenolate and a reduction in the use of cyclosporin and azathioprine use as baseline immunosuppression to prevent acute rejection. There are also global variations in use of polyclonal and monoclonal antibodies to treat acute rejection. This is an update of a review published in 2006.

OBJECTIVES

The aim of this systematic review was to: (1) to evaluate the relative and absolute effects of different classes of antibody preparation in preventing graft loss and resolving cellular or humoral rejection episodes when used as a treatment for first episode of rejection in kidney transplant recipients; (2) evaluate the relative and absolute effects of different classes of antibody preparation in preventing graft loss and resolving cellular or humoral rejection episodes when used as a treatment for steroid-resistant rejection in kidney transplant recipients; (3) determine how the benefits and adverse events vary for each type of antibody preparation; and (4) determine how the benefits and harms vary for different formulations of antibody within each type.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 18 April 2017 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in all languages comparing all mono- and polyclonal antibody preparations, given in combination with any other immunosuppressive agents, for the treatment of cellular or humoral graft rejection, when compared to any other treatment for acute rejection were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias of the included studies and extracted data. Statistical analyses were performed using a random-effects model and results expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 new studies (18 reports, 346 participants) in this update, bring the total number of included studies to 31 (76 reports, 1680 participants). Studies were generally small, incompletely reported, especially for potential harms, and did not define outcome measures adequately. The risk of bias was inadequate or unclear risk for random sequence generation (81%), allocation concealment (87%) and other bias (87%). There were, however, a predominance of low risk of bias for blinding (75%) and incomplete outcome data (80%) across all the studies. Selective reporting had a mixture of low (58%), high (29%), and unclear (13%) risk of bias.Seventeen studies (1005 participants) compared therapies for first acute cellular rejection episodes. Antibody therapy was probably better than steroid in reversing acute cellular rejection (RR 0.50, 95% CI 0.30 to 0.82; moderate certainty) and preventing subsequent rejection (RR 0.70, 95% CI 0.50 to 0.99; moderate certainty), may be better for preventing graft loss (death censored: (RR 0.80, 95% CI 0.57 to 1.12; low certainty) but there was little or no difference in death at one year. Adverse effects of treatment (including fever, chills and malaise following drug administration) were probably reduced with steroid therapy (RR 23.88, 95% CI 5.10 to 111.86; I2 = 16%; moderate certainty).Twelve studies (576 patients) investigated antibody treatment for steroid-resistant rejection. There was little or no benefit of muromonab-CD3 over ATG or ALG in reversing rejection, preventing subsequent rejection, or preventing graft loss or death. Two studies compared the use of rituximab for treatment of acute humoral rejection (58 patients). Muromonab-CD3 treated patients suffered three times more than those receiving either ATG or T10B9, from a syndrome of fever, chills and malaise following drug administration (RR 3.12, 95% CI 1.87 to 5.21; I2 = 31%), and experienced more neurological side effects (RR 13.10 95% CI 1.43 to 120.05; I2 = 36%) (low certainty evidence).There was no evidence of additional benefit from rituximab in terms of either reversal of rejection (RR 0.94, 95% CI 0.54 to 1.64), or graft loss or death 12 months (RR 1.0, 95% CI 0.23 to 4.35). Rituximab plus steroids probably increases the risk of urinary tract infection/pyelonephritis (RR 5.73, 95% CI 1.80 to 18.21).

AUTHORS' CONCLUSIONS

In reversing first acute cellular rejection and preventing graft loss, any antibody is probably better than steroid, but there is little or no difference in subsequent rejection and patient survival. In reversing steroid-resistant rejection there was little or no difference between different antibodies over a period of 12 months, with limited data beyond that time frame. In treating acute humoral rejection, there was no evidence that the use of antibody therapy conferred additional benefit in terms of reversal of rejection, or death or graft loss.Although this is an updated review, the majority of newer included studies provide additional evidence from the cyclosporin/azathioprine era of kidney transplantation and therefore conclusions cannot necessarily be extrapolated to patients treated with more contemporary immunosuppressive regimens which include tacrolimus/mycophenolate or sirolimus. However, many kidney transplant centres around the world continue to use older immunosuppressive regimes and the findings of this review remain strongly relevant to their clinical practice.Larger studies with standardised reproducible outcome criteria are needed to investigate the outcomes and risks of antibody treatments for acute rejection in kidney transplant recipients receiving contemporary immunosuppressive regimes.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Rejection of the Renal Allograft in the Absence of Demonstrable Antibody and Complement

BACKGROUND

Recent literature has stressed the prominent role of antibodies in graft loss. This study was designed to assess a growing perception that T cell-mediated rejection (TCMR) is no longer clinically relevant.

METHODS

Five hundred forty-five renal allograft recipients over a 3-year period were screened for biopsies with: (a) TCMR including borderline change (BL), (b) negative complement protein C4 degradation fragment, and (c) absence of donor-specific antibody at time of transplant, within 30 days of the biopsy, and up to 4 measurements at later time points.

RESULTS

These stringent requirements identified 28 "pure" cases of late TCMR/BL. Low-grade glomerulitis, peritubular capillaritis, or chronic transplant glomerulopathy were found in 9/28 (32%) biopsies. Serum creatinine showed complete short-term remission in 7/10 (70%) BL and 9/18 (50%) TCMR patients 1 month postbiopsy. Yet, both treated and untreated patients demonstrated further decline in graft function as assessed by serum creatinine and estimated glomerular filtration rate.

CONCLUSIONS

Late TCMR seen in 7.9% of biopsies can contribute to significant deterioration of graft function in patients in whom the dominant contribution of antibody-mediated injury has been reasonably excluded. Our data also reinforce existing literature showing that microvascular lesions do not have absolute specificity for a diagnosis of antibody-mediated rejection.

Does copy number variation of APOL1 gene affect the susceptibility to focal segmental glomerulosclerosis?

Background: APOL1 risk variants (G1 and G2) are associated with increased susceptibility to focal segmental glomerulosclerosis (FSGS) in African population. However, the two risk mutations were not found in Chinese FSGS patients. In this study, we explored the association between the copy number variation (CNV) of APOL1 gene and FSGS.

Methods: APOL1 copy number variations were detected by quantitative real-time PCR with TaqMan probes and compared between 133 FSGS patients and 123 controls. The association between CNV of APOL1 gene and clinical parameters was also investigated.

Results: The distribution of APOL1 CNV did not show significant difference between FSGS patients and controls. The creatinine and proteinuria in the high copy number group (CN ≥ 3) were higher than the other two groups, but the difference was not significant (p > .05). The FSGS pathological types were different among the three groups.

Conclusion: There was no significant difference in the distribution of APOL1 gene copy variants between FSGS patients and normal controls, and there was no significant correlation between the APOL1 gene CNV and the FSGS patients’ clinical manifestations. APOL1 CNVs may be not associated with susceptibility to FSGS.

Immunohistopathologic Characterization of Plasma Cell-Rich Acute Rejection in Living-Related Renal Transplant Recipients

OBJECTIVES

Our aim was to analyze the immunohistopathologic features of plasma cell-rich acute rejection in a living-related renal transplant setting.

MATERIALS AND METHODS

Renal allograft biopsies of 50 cases of plasma cell-rich acute rejection were reviewed, and the main immunohistopathologic features were analyzed. The biopsies were studied using light microscopy, immunofluorescence, and immunohistochemistry and reported according to Banff classification. Biopsy findings were correlated with graft function and outcome.

RESULTS

From February 2012 to December 2013, 50/1630 (3%) dysfunctional renal allograft biopsies showed plasma cell-rich acute rejection. Among acute changes, interstitial inflammation was of moderate degree in 8 cases (16%) and severe in 42 cases (84%). Mild tubulitis was found in 4 cases (8%), moderate tubulitis in 8 cases (16%), and severe tubulitis in 38 cases (76%). Glomerulitis was found in 2 cases (4%). No presence of arteritis was found. All plasma cell-rich acute rejection cases were of tubulointerstitial type, and most were of type IB. The mean percent of plasma cells on light microscopy in all cases was 28.8 ± 11.7%, and the range was 10% to 60%, with 46 cases (92%) showing plasma cell percent of ≥ 20%. The mean plasma cell percent on immunohistochemistry for CD138 was 29.0 ± 12.4%. Microvascular inflammation was found in 34 cases (68%). C4d testing was done by immunofluorescence in 22 cases (44%) and was positive in 8 cases (36%). Interstitial fibrosis/tubular atrophy was mild in 18 (36%), moderate in 28 (56%), and severe in 4 cases (8%). Plasma cell enrichment did not correlate with a variety of clinical and pathologic features (all P > .05).

CONCLUSIONS

Plasma cell enrichment is not an independent prognostic morphologic feature and may represent either T-cell-mediated or antibody-mediated rejection or a mixture of these processes. Further investigations regarding its pathogenesis, accurate categorization, and treatment are needed.

Relationship between diurnal blood pressure and renal histopathological changes in white coat hypertension

BACKGROUND

Multiple epidemiological studies have clearly demonstrated the macrovascular risks associated with white coat hypertension (WCH) or sustained hypertension (SH). In patients with WCH, there is no literature available on renal histopathological changes and that on blood pressure pattern and native kidney outcome is scant. We aimed to clarify the relationship between blood pressure variables and pathological features of kidney biopsies in living kidney donors with WCH.

METHODS

This cross-sectional study included living kidney donors with WCH (n = 10) and SH (n = 10), and 20 healthy kidney donors with similar demographic features (control group). Kidney allograft biopsy samples were obtained during transplantation and chronic glomerular, vascular and tubulointertitial changes were semiquantitatively scored according to the Banff classification.

RESULTS

The mean age of the 20 hypertensive subjects (Group 1) and controls (Group 2) was 59.3 ± 8.5 versus 59.6 ± 7.6 years and almost half were female. There was no difference in renal function parameters between the groups; however, kidney histopathology in Group 1 was worse than Group 2 with a chronicity index of 2.80 ± 1.67 versus 1.75 ± 1.16 (p = 0.02). There was no difference between histopathological scores of patients with WCH or SH (chronicity index: 2.60 ± 1.43 vs. 2.70 ± 1.70, p = 0.88). Night-to-day mean arterial pressure (MAP) ratio was significantly associated with chronicity index in patients with WCH. Moreover, WCH patients with non-dipper hypertensive pattern had a worse chronicity index.

CONCLUSIONS

Significant histopathological alterations in the kidney were observed in patients with WCH and SH, and were accentuated in WCH patients with non-dipper blood pressure pattern.

Current status of pediatric renal transplant pathology

Histopathology is still an indispensable tool for the diagnosis of kidney transplant dysfunction in adult and pediatric patients. This review presents consolidated knowledge, recent developments and future prospects on the biopsy procedure, the diagnostic work-up, classification schemes, the histopathology of rejection, including antibody-mediated forms, ABO-incompatible transplants, protocol biopsies, recurrent and de novo disease, post-transplant lymphoproliferative disorder, infectious complications and drug-induced toxicity. It is acknowledged that frequently the correct diagnosis can only be reached in consensus with clinical, serological, immunogenetical, bacteriological and virological findings. This review shall enhance the understanding of the pediatric nephrologist for the thought processes of nephropathologists with the aim to facilitate teamwork between these specialist groups for the benefit of the patient.

Early Macrophage Infiltration and Sustained Inflammation in Kidneys From Deceased Donors Are Associated With Long-Term Renal Function

Kidney transplants from living donors (LDs) have a better outcome than those from deceased donors (DDs). Different factors have been suggested to justify the different outcome. In this study, we analyzed the infiltration and phenotype of monocytes/macrophages and the expression of inflammatory and fibrotic markers in renal biopsy specimens from 94 kidney recipients (60 DDs and 34 LDs) at baseline and 4 months after transplantation. We evaluated their association with medium- and long-term renal function. At baseline, inflammatory gene expression was higher in DDs than in LDs. These results were confirmed by the high number of CD68-positive cells in DD kidneys, which correlated negatively with long-term renal function. Expression of the fibrotic markers vimentin, fibronectin, and α-smooth muscle actin was more elevated in biopsy specimens from DDs at 4 months than in those from LDs. Gene expression of inflammatory and fibrotic markers at 4 months and difference between 4 months and baseline correlated negatively with medium- and long-term renal function in DDs. Multivariate analysis point to transforming growth factor-β1 as the best predictor of long-term renal function in DDs. We conclude that early macrophage infiltration, sustained inflammation, and transforming growth factor-β1 expression, at least for the first 4 months, contribute significantly to the difference in DD and LD transplant outcome.

Clinical and pathological analyses of interstitial fibrosis and tubular atrophy cases after kidney transplantation

AIM

We carried out a clinicopathological analysis of cases presenting with interstitial fibrosis and tubular atrophy (IF/TA) after renal transplantation in an attempt to clarify the mechanisms underlying the development and prognostic significance of IF/TA.

METHODS

IF/TA was diagnosed in 35 renal allograft biopsy specimens (BS) obtained from 35 renal transplant recipients under follow up at the Department of Transplant Surgery, Kidney Center, Toda Chuo General Hospital, between January 2014 and March 2015.

RESULTS

IF/TA was diagnosed at a median of 39.9 months after the transplantation. Among the 35 patients with IF/TA, 19 (54%) had a history of acute rejection. Among the 35 BS showing evidence of IF/TA, the IF/TA was grade I in 25, grade II in 9, and grade III in 1. Arteriosclerosis of the middle-sized arteries was observed in 30 BS (86%). We then classified the 35 BS showing evidence of IF/TA according to their overall histopathological features, as follows; IF/TA alone (6 BS; 17%), IF/TA + medullary ray injury (12 BS; 34%), and IF/TA + rejection (12 BS; 34%). Loss of the renal allograft occurred during the observation period in one of the patients (3%). Of the remaining patients with functioning grafts, deterioration of the renal allograft function after the biopsies occurred in 15 patients (43%).

CONCLUSIONS

The results of our study suggests that rejection contributes to IF/TA in 30-40% of cases, medullary ray injury in 30-40% of cases, and nonspecific injury in 20% of cases. IF/TA contributes significantly to deterioration of renal allograft function.

Detection of Donor-Derived Microparticles in the Peripheral Blood of a Hand Transplant Recipient During Rejection

BACKGROUND

Microparticles (MPs) are released from the plasma membrane of activated or dying cells and bear surface molecules from those cells. We examined whether donor-derived MPs in the peripheral blood of the recipient could serve as a marker of tissue damage due to rejection of a transplanted hand.

METHODS

Platelet-free plasma from the recipient of the transplanted hand was analyzed for MPs bearing the donor-specific HLA molecule A*02 using flow cytometry. Rejection status of the transplanted hand was monitored by histopathology of skin punch biopsies.

RESULTS

Donor-specific MPs expressing HLA A*02 were quantifiable in the peripheral blood of the recipient. Levels of these MPs increased with worsening rejection of the transplanted hand.

CONCLUSIONS

These findings demonstrate the ability to detect donor specific MPs through staining of graft cell-specific HLA and promote further investigation into the potential utility of flow cytometry for donor-derived MPs as a noninvasive tool to assess rejection in solid organ transplantation patients.

Renal Transplant Patients Biopsied for Cause and Tested for C4d, DSA, and IgG Subclasses and C1q: Which Humoral Markers Improve Diagnosis and Outcomes?

The association between donor specific antibodies (DSA) and renal transplant rejection has been generally established, but there are cases when a DSA is present without rejection. We examined 73 renal transplant recipients biopsied for transplant dysfunction with DSA test results available: 23 patients diffusely positive for C4d (C4d+), 25 patients focally positive for C4d, and 25 patients negative for C4d (C4d−). We performed C1q and IgG subclass testing in our DSA+ and C4d+ patient group. Graft outcomes were determined for the C4d+ group. All 23 C4d+ patients had IgG DSA with an average of 12,500 MFI (cumulative DSA MFI). The C4d− patients had average DSA less than 500 MFI. Among the patients with C4d+ biopsies, 100% had IgG DSA, 70% had C1q+ DSA, and 83% had complement fixing IgG subclass antibodies. Interestingly, IgG4 was seen in 10 of the 23 recipients' sera, but always along with complement fixing IgG1, and we have previously seen excellent function in patients when IgG4 DSA exists alone. Cumulative DSA above 10,000 MFI were associated with C4d deposition and complement fixation. There was no significant correlation between graft loss and C1q positivity, and IgG subclass analysis seemed to be a better correlate for complement fixing antibodies in the C4d+ patient group.

Current pathological perspectives on chronic rejection in renal allografts

Chronic rejection in renal transplantation clinically manifests as slow deterioration in allograft function and is a major contributor of late renal graft loss. Most cases of chronic rejection involve chronic antibody-mediated rejection (ABMR) triggered by the interaction of donor-specific alloantibodies with endothelial cells of the microcirculation. The evolution of the Banff classification involved a major revision of the ABMR criteria during the 2000s and led to the inclusion of detailed pathological characteristics of chronic ABMR in the 2013 Banff scheme, including microcirculation damage observed as newly formed basement membranes and arterial fibrous intimal proliferation. Inflammation of microvasculature including glomeruli and/or peritubular capillaries is also seen in substantial cases of chronic ABMR, defined as chronic active ABMR. Chronic active T cell-mediated rejection (TCMR) results from chronic T cell-mediated injury involving renal arteries but is less characterized under the current Banff classification, mainly due to the expanding histological criteria of chronic active ABMR. Characteristics shared by these two chronic rejection types can potentially cause diagnostic confusion. Hence, the diagnostic criteria or categories of chronic renal rejection require amendment of the current Banff classification. Assessment of rejection cases with molecular phenotyping advanced the mechanistic understanding of various dysfunctions in renal allograft, including ABMR and TCMR. Identification of disease-specific changes in gene expression by immunohistological studies, especially in chronic ABMR, has already been validated by several studies, warranting potential application to the pathological diagnostic process. This review provides an overview of current pathological perspectives on chronic rejection of renal allografts and future directions.

Incidence, risk factors, and the impact of allograft pyelonephritis on renal allograft function

BACKGROUND

The impact of allograft pyelonephritis (AGPN) on renal allograft function is controversial. In this study, we evaluated the incidence, risk factors, and the impact of AGPN on renal allograft function.

METHODS

Retrospective cohort study in adult renal allograft recipients with 1-year follow-up after transplantation (Tx). Renal allograft function was evaluated by estimated glomerular filtration rate (eGFR) (by Modification of Diet in Renal Disease formula) and 24-h urine protein excretion.

RESULTS

A total of 431 renal allograft recipients were analyzed; 57 (13.2%) developed AGPN within 1 year after Tx. Median time between Tx and AGPN was 50 days. Risk factors for AGPN were the presence of a urological catheter (odds ratio [OR] = 18.93, 95% confidence interval [CI] = 8.00-44.81, P < 0.001) and preceding asymptomatic bacteriuria (ASB) (OR = 2.16, 95% CI = 1.20-3.90, P = 0.009). In 72.7%, the causative microorganism of ASB was identical to that of the succeeding AGPN episode. Multivariable linear regression analysis showed that experiencing AGPN did not decrease the eGFR (P = 0.61) nor did increased proteinuria (P = 0.29) 1 year after Tx. For the eGFR, an interaction was found between AGPN/bacteriuria (BU) and acute rejection (AR): the group experiencing BU preceding AR had significantly (P < 0.001) lower eGFR compared with the group that experienced only AR (21 mL/min/1.73 m² vs. 48 mL/min/1.73 m² ), as a result of increased prevalence of combined rejections within the BU group.

CONCLUSION

Indwelling urological catheters and preceding ASB are associated with developing AGPN. An incident of AGPN itself does not impair renal allograft function 1 year after Tx. However, a relevant interaction occurs between BU and AR, in which the sequence of occurrence of these 2 events synergistically impairs the eGFR.

Banff Borderline Changes Suspicious for Acute T Cell-Mediated Rejection: Where Do We Stand?

The definition of Banff Borderline became ambiguous when the Banff 2005 consensus modified the lower threshold from i1t1 (10-25% interstitial inflammation with mild tubulitis) to i0t1 (0-10% interstitial inflammation with mild tubulitis). We conducted a worldwide survey among members of the Renal Pathology Society about their approach to this diagnostic category. A web-based survey was sent out to all 503 current members (153 respondents). A database search yielded which threshold for Banff i was applied in the most influential manuscripts about Borderline. Among the 139 nephropathologists using the Borderline category, 67% use the Banff 1997 definition, requiring Banff i1. Thirty-seven percent admitted to sometimes exaggerating Banff i in the presence of tubulitis, to reach a diagnosis of Borderline. Forty-eight percent were dissatisfied with the definition of Borderline. The majority of the most influential manuscripts used the 1997 definition, contrary to the current one. There is considerable dissatisfaction with Borderline, and practice in Banff i thresholds is variable. Until additional studies inform a revision, we suggest leaving it to each pathologist's discretion whether to use i0 or i1 as the minimal threshold. In order to avoid future ambiguity, a web-based synopsis of all scattered current Banff definitions and rules should be created.

Renal graft survival according to Banff 2013 classification in indication biopsies

INTRODUCTION

The impact of acute rejection in kidney graft survival is well known, but the prognosis of other diagnoses is uncertain. We evaluated the frequency and impact on graft survival of different diagnostic categories according to the Banff 2013 classification in a cohort of renal transplant recipients.

MATERIAL AND METHODS

Retrospective study of 495 renal biopsies by indication in 322 patients from 1990-2014. Two independent observers reviewed the histological reports, reclassifying according to the Banff 2013 classification.

RESULTS

Of 495 biopsies, 28 (5.7%) were not diagnostic. Of the remaining 467, 10.3% were «normal» (category 1), 19.6% antibody-mediated changes (category 2), 5.9% «borderline» changes (category 3), 8.7% T-cell-mediated rejection (category 4), 23.4% interstitial fibrosis/tubular atrophy (IFTA) (category 5) and 26.5% with other diagnoses (category 6). As time after transplantation increases, diagnoses of categories 1, 3 and 4 decrease, while categories 5 and 2 increase. Worse graft survival with category 2 diagnosis was observed (45% at 7.5 years, HR 4.29 graft loss [95% CI, 2.39-7.73]; P≤.001, compared to category 1). Grafts with «unfavourable histology» (chronic antibody-mediated rejection, moderate-severe IFTA) presented worse survival that grafts with «favourable histology» (normal, acute tubular necrosis, mild IFTA).

CONCLUSIONS

The Banff 2013 classification facilitates a histological diagnosis in 95% of indication biopsies. While diagnostic category 6 is the most common, a change in the predominant histopathology was observed according to time elapsed since transplantation. Antibody-mediated changes are associated with worse graft survival.

Posttransplant Lymphoproliferative Disorders

Posttransplant lymphoproliferative disorders (PTLD) are an acknowledged complica tion of transplantation and immunosuppression that may be difficult to distinguish from severe rejection in small biopsy specimens. In this study we compared 19 exam ples of PTLD with 20 cases of severe rejection. Antibodies to CD20, CD43, CD45, CD45RO, MB2, Epstein-Barr virus-latent membrane protein, bcl-2 , proliferating cell nuclear antigen, cytomegalovirus early antigen, and hepatitis B surface and core anti gens were employed. The results expressed as percentage of positive cases of PTLD/ rejection, were: CD20, 89/0; CD43, 63/100; CD45, 100/100; CD45RO, 5/85; MB2, 32/0; Epstein-Barr virus-latent membrane protein, 79/0. Aberrant coexpression of CD20 and CD43 was seen in 11 cases of PTLD and no cases of severe rejection. The proliferating cell nuclear antigen index was 58% in PTLD cases, and 20% in rejection; stains for bcl-2 protein were nondiscriminatory. No examples of either process were reactive for cytomegalovirus or hepatitis B antigens. These results indicate that PTLD usually has a B-cell phenotype, often with associated necrosis, while acute rejection is a T-cell process. Expression of Epstein-Barr virus-latent membrane protein, and coexpression of CD43 and CD20 are additional attributes of PTLD. Int J Surg Pathol 2(2):105-116, 1994

New Magnetic Resonance Imaging Index for Renal Fibrosis Assessment: A Comparison between Diffusion-Weighted Imaging and T1 Mapping with Histological Validation

A need exists to noninvasively assess renal interstitial fibrosis, a common process to all kidney diseases and predictive of renal prognosis. In this translational study, Magnetic Resonance Imaging (MRI) T1 mapping and a new segmented Diffusion-Weighted Imaging (DWI) technique, for Apparent Diffusion Coefficient (ADC), were first compared to renal fibrosis in two well-controlled animal models to assess detection limits. Validation against biopsy was then performed in 33 kidney allograft recipients (KARs). Predictive MRI indices, ΔT1 and ΔADC (defined as the cortico-medullary differences), were compared to histology. In rats, both T1 and ADC correlated well with fibrosis and inflammation showing a difference between normal and diseased kidneys. In KARs, MRI indices were not sensitive to interstitial inflammation. By contrast, ΔADC outperformed ΔT1 with a stronger negative correlation to fibrosis (R² = 0.64 against R² = 0.29 p < 0.001). ΔADC tends to negative values in KARs harboring cortical fibrosis of more than 40%. Using a discriminant analysis method, the ΔADC, as a marker to detect such level of fibrosis or higher, led to a specificity and sensitivity of 100% and 71%, respectively. This new index has potential for noninvasive assessment of fibrosis in the clinical setting.

The epidermal growth factor receptor pathway in chronic kidney diseases

The epidermal growth factor receptor (EGFR) pathway has a critical role in renal development, tissue repair and electrolyte handling. Numerous studies have reported an association between dysregulation of this pathway and the initiation and progression of various chronic kidney diseases such as diabetic nephropathy, chronic allograft nephropathy and polycystic kidney disease through the promotion of renal cell proliferation, fibrosis and inflammation. In the oncological setting, compounds that target the EGFR pathway are already in clinical use or have been evaluated in clinical trials; in the renal setting, therapeutic interventions targeting this pathway by decreasing ligand availability with disintegrin and metalloproteinase inhibitors or with ligand-neutralizing antibodies, or by inhibiting receptor activation with tyrosine kinase inhibitors or monoclonal antibodies are only just starting to be explored in animal models of chronic kidney disease and in patients with autosomal dominant polycystic kidney disease. In this Review we focus on the role of the EGFR signalling pathway in the kidney under physiological conditions and during the pathophysiology of chronic kidney diseases and explore the clinical potential of interventions in this pathway to treat chronic renal diseases.

Impact of the Banff 2013 classification on the diagnosis of suspicious versus conclusive late antibody-mediated rejection in allografts without acute dysfunction

BACKGROUND

The Banff classification is used worldwide to characterize pathological findings in renal allograft biopsies. During the 11th Banff meeting, relevant changes were introduced in the diagnostic criteria for Category 2 antibody-mediated rejection (ABMR). Here, we assess the effect of these changes on the diagnosis of late chronic ABMR.

METHODS

Seventy-three indication renal graft biopsies (chronic dysfunction, proteinuria and/or the presence of de novo donor-specific antibodies) from 68 kidney transplant recipients initially classified following the Banff 2009 criteria were reviewed and reclassified as per the new Banff 2013 criteria.

RESULTS

The diagnostic category changed in 18% of the study biopsies with Banff 2013. The reclassification mainly involved Category 2 cases, from which 23.5% of the biopsies from older patients with worse graft function were overlooked by Banff 2009. ABMR was ruled out in 13% of cases under the Banff 2009 criteria. A significant number of the study samples were conclusively diagnosed as ABMR (40% as per Banff 2009 and 74% as per Banff 2013; P = 0.006), because of the inclusion of microvascular inflammation and the acceptance of some ultrastructural diagnostic criteria. However, when following the criteria of the new classification, samples with histological signs of chronic ABMR, in which human leucocyte antigen donor-specific antibodies are not detected or ultrastructural studies are not performed, may be inadequately characterized.

CONCLUSIONS

The Banff 2013 classification helps in making a diagnosis of late ABMR, identifying cases, decreasing the percentage of suspected ABMR and making more conclusive diagnoses.

The Application of Digital Pathology to Improve Accuracy in Glomerular Enumeration in Renal Biopsies

Background

In renal biopsy reporting, quantitative measurements, such as glomerular number and percentage of globally sclerotic glomeruli, is central to diagnostic accuracy and prognosis. The aim of this study is to determine the number of glomeruli and percent globally sclerotic in renal biopsies by means of registration of serial tissue sections and manual enumeration, compared to the numbers in pathology reports from routine light microscopic assessment.

Design

We reviewed 277 biopsies from the Nephrotic Syndrome Study Network (NEPTUNE) digital pathology repository, enumerating 9,379 glomeruli by means of whole slide imaging. Glomerular number and the percentage of globally sclerotic glomeruli are values routinely recorded in the official renal biopsy pathology report from the 25 participating centers. Two general trends in reporting were noted: total number per biopsy or average number per level/section. Both of these approaches were assessed for their accuracy in comparison to the analogous numbers of annotated glomeruli on WSI.

Results

The number of glomeruli annotated was consistently higher than those reported (p<0.001); this difference was proportional to the number of glomeruli. In contrast, percent globally sclerotic were similar when calculated on total glomeruli, but greater in FSGS when calculated on average number of glomeruli (p<0.01). The difference in percent globally sclerotic between annotated and those recorded in pathology reports was significant when global sclerosis is greater than 40%.

Conclusions

Although glass slides were not available for direct comparison to whole slide image annotation, this study indicates that routine manual light microscopy assessment of number of glomeruli is inaccurate, and the magnitude of this error is proportional to the total number of glomeruli.

Immune response and histology of humoral rejection in kidney transplantation

The adaptive immune response forms the basis of allograft rejection. Its weapons are direct cellular cytotoxicity, identified from the beginning of organ transplantation, and/or antibodies, limited to hyperacute rejection by preformed antibodies and not as an allogenic response. This resulted in allogenic response being thought for decades to have just a cellular origin. But the experimental studies by Gorer demonstrating tissue damage in allografts due to antibodies secreted by B lymphocytes activated against polymorphic molecules were disregarded. The special coexistence of binding and unbinding between antibodies and antigens of the endothelial cell membranes has been the cause of the delay in demonstrating the humoral allogenic response. The endothelium, the target tissue of antibodies, has a high turnover, and antigen-antibody binding is non-covalent. If endothelial cells are attacked by the humoral response, immunoglobulins are rapidly removed from their surface by shedding and/or internalization, as well as degrading the components of the complement system by the action of MCP, DAF and CD59. Thus, the presence of complement proteins in the membrane of endothelial cells is transient. In fact, the acute form of antibody-mediated rejection was not demonstrated until C4d complement fragment deposition was identified, which is the only component that binds covalently to endothelial cells. This review examines the relationship between humoral immune response and the types of acute and chronic histological lesion shown on biopsy of the transplanted organ.

Pre-transplant end-stage renal disease-related immune risk profile in kidney transplant recipients predicts post-transplant infections

BACKGROUND

End-stage renal disease (ESRD) is associated with premature aging of the T-cell system. Nevertheless, the clinical significance of pre-transplant ESRD-related immune senescence is unknown.

METHODS

We studied whether immune risk phenotype (IRP), a typical feature of immune senescence, may affect post-transplant infectious complications. A total of 486 patients were prospectively studied during the first year post transplant. IRP was defined as positive cytomegalovirus serology with at least 1 of the following criteria: CD4/CD8 ratio <1 and/or CD8 T-cell count >90th percentile.

RESULTS

We found that 47 patients (9.7%) had pre-transplant IRP. IRP+ patients did not differ from IRP- patients for any clinical characteristics, but exhibited more pronounced immune senescence. Both opportunistic infections (43% vs. 6%, P < 0.001) and severe bacterial infection (SBI) (40% vs. 25%, P = 0.028) were more frequent in IRP(+) patients. In multivariate analysis, IRP was predictive of both opportunistic infection (hazard ratio [HR] 2.97 [95% confidence interval {CI} 1.53-5.76], P = 0.001), and SBI (HR 2.33 [95% CI 1.34-3.92], P = 0.008). Acute rejection rates were numerically much lower in IRP+ patients. A total of 418 patients (86%) had biological evaluation 1 year post transplant. Among 41 IRP+ patients, 35 (85%) remained IRP+ 1 year post transplant.

CONCLUSION

Pre-transplant IRP is associated with an increased risk of post-transplant infection.

Total inflammation in early protocol kidney graft biopsies does not predict progression of fibrosis at one year post-transplant

INTRODUCTION

There is an uncertainty whether total inflammation in early protocol kidney graft biopsies is associated with fibrosis progression. We investigated whether total inflammation, both in fibrotic and non-fibrotic areas, at week 6 would predict fibrosis progression at one yr post-transplant.

METHODS

We included 156 single adult ABO compatible kidney recipients with adequate week 6 and one yr transplant protocol biopsies (312 biopsies). Biopsies were scored according to the current Banff criteria. In addition, fibrosis and inflammation in fibrotic and non-fibrotic areas were scored in a 10-grade semi-quantitative eyeballing system from 0% to 100%.

RESULTS

Fibrosis increased significantly from week 6 to one yr both by the 10-grade scoring system from 0.69 ± 1.07 to 1.45 ± 1.86, (mean ± SD), p < 0.001 and by Banff interstitial fibrosis (ci) scoring 0.81 ± 0.65 to 1.13 ± 0.87, p < 0.001. The 10-grade scoring system detected a larger proportion of fibrosis progressors than the Banff scoring 40.4% vs. 35.5%, p < 0.001. No significant positive association was found between inflammation at week 6 and progression of fibrosis in either of the scoring systems.

CONCLUSIONS

Total inflammation in kidney transplant biopsies at week 6 did not predict progression of fibrosis at one yr post-transplant.

Augmentation of Transient Donor Cell Chimerism and Alloantigen-Specific Regulation of Lung Transplants in Miniature Swine

Donor alloantigen infusion induces T cell regulation and transplant tolerance in small animals. Here, we study donor splenocyte infusion in a large animal model of pulmonary transplantation. Major histocompatibility complex-mismatched single lung transplantation was performed in 28 minipigs followed by a 28-day course of methylprednisolone and tacrolimus. Some animals received a perioperative donor or third party splenocyte infusion, with or without low-dose irradiation (IRR) before surgery. Graft survival was significantly prolonged in animals receiving both donor splenocytes and IRR compared with controls with either donor splenocytes or IRR only. In animals with donor splenocytes and IRR, increased donor cell chimerism and CD4(+) CD25(high+) T cell frequencies were detected in peripheral blood associated with decreased interferon-γ production of leukocytes. Secondary third-party kidney transplants more than 2 years after pulmonary transplantation were acutely rejected despite maintained tolerance of the lung allografts. As a cellular control, additional animals received third-party splenocytes or donor splenocyte protein extracts. While animals treated with third-party splenocytes showed significant graft survival prolongation, the subcellular antigen infusion showed no such effect. In conclusion, minipigs conditioned with preoperative IRR and donor, or third-party, splenocyte infusions may develop long-term donor-specific pulmonary allograft survival in the presence of high levels of circulating regulatory T cells.

The Revised (2013) Banff Classification for Antibody-Mediated Rejection of Renal Allografts: Update, Difficulties, and Future Considerations

The Banff 2013 classification (Banff 2013) for antibody-mediated rejection (ABMR) in renal allografts represents the first major revision of the original Banff classification for ABMR that was published in 2003. The main impetus for this revision was the need to include C4d-negative ABMR, although this revised classification contains a number of additional features based on findings reported from 2007 to 2013. Since its publication, several studies have examined the validity of different aspects of Banff 2013 and compared it to earlier (2003, 2007) versions of the Banff ABMR classification. Recent evidence, albeit limited, indicates that Banff 2013 represents an improvement over the previous versions, enhancing our ability to accurately diagnose cases of acute/active and chronic active ABMR on renal allograft biopsy. Molecular studies appear to justify the threshold value of glomerulitis plus peritubular capillaritis score ≥2 required by Banff 2013 for the diagnosis of C4d-negative ABMR; however, other aspects of the classification, including its overall interobserver reproducibility, the clinical significance of the category of C4d staining without evidence of rejection, and whether surrogate markers might potentially substitute for the requirement for the presence of donor-specific antibodies, require additional investigation.

Impact of specimen adequacy on the assessment of renal allograft biopsy specimens

The Banff classification was introduced to achieve uniformity in the assessment of renal allograft biopsies. The primary aim of this study was to evaluate the impact of specimen adequacy on the Banff classification. All renal allograft biopsies obtained between July 2010 and June 2012 for suspicion of acute rejection were included. Pre-biopsy clinical data on suspected diagnosis and time from renal transplantation were provided to a nephropathologist who was blinded to the original pathological report. Second pathological readings were compared with the original to assess agreement stratified by specimen adequacy. Cohen's kappa test and Fisher's exact test were used for statistical analyses. Forty-nine specimens were reviewed. Among these specimens, 81.6% were classified as adequate, 6.12% as minimal, and 12.24% as unsatisfactory. The agreement analysis among the first and second readings revealed a kappa value of 0.97. Full agreement between readings was found in 75% of the adequate specimens, 66.7 and 50% for minimal and unsatisfactory specimens, respectively. There was no agreement between readings in 5% of the adequate specimens and 16.7% of the unsatisfactory specimens. For the entire sample full agreement was found in 71.4%, partial agreement in 20.4% and no agreement in 8.2% of the specimens. Statistical analysis using Fisher's exact test yielded a P value above 0.25 showing that - probably due to small sample size - the results were not statistically significant. Specimen adequacy may be a determinant of a diagnostic agreement in renal allograft specimen assessment. While additional studies including larger case numbers are required to further delineate the impact of specimen adequacy on the reliability of histopathological assessments, specimen quality must be considered during clinical decision making while dealing with biopsy reports based on minimal or unsatisfactory specimens.