Acute renal allograft rejection with severe tubulitis (Banff 1997 grade IB)

Evolution of human kidney allograft pathology diagnostics through 30 years of the Banff classification process

The second half of the previous century witnessed a tremendous rise in the number of clinical kidney transplants worldwide. This activity was, however, accompanied by many issues and challenges. An accurate diagnosis and appropriate management of causes of graft dysfunction were and still are, a big challenge. Kidney allograft biopsy played a vital role in addressing the above challenge. However, its interpretation was not standardized for many years until, in 1991, the Banff process was started to fill this void. Thereafter, regular Banff meetings took place every 2 years for the past 30 years. Marked changes have taken place in the interpretation of kidney allograft biopsies, diagnosis, and classification of rejection and other non-rejection pathologies from the original Banff 93 classification. This review attempts to summarize those changes for increasing the awareness and understanding of kidney allograft pathology through the eyes of the Banff process. It will interest the transplant surgeons, physicians, pathologists, and allied professionals associated with the care of kidney transplant patients.

Unsatisfactory reproducibility of interstitial inflammation scoring in allograft kidney biopsy

Interstitial inflammation scoring is incorporated into the Banff Classification of Renal Allograft Pathology and is essential for the diagnosis of T-cell mediated rejection. However, its reproducibility, including inter-rater and intra-rater reliabilities, has not been carefully investigated. In this study, eight renal pathologists from different hospitals independently scored 45 kidney allograft biopsies with varying extents of interstitial inflammation. Inter-rater reliabilities and intra-rater reliabilities were investigated by kappa statistics and conditional agreement probabilities. Individual pathologists' scoring patterns were examined by chi-squared tests and proportions tests. The mean pairwise kappa values for inter-rater reliability were 0.27, 0.30, and 0.26 for the Banff i score, ti score, and i-IFTA, respectively. No rater pair performed consistently better or worse than others on all three scorings. After dichotomizing the scores into two groups (none/mild and moderate/severe inflammation), the averaged conditional agreements ranged from 47.1% to 50.0%. The distributions of the scores differed, but some pathologists persistently scored higher or lower than others. Given the important role of interstitial inflammation scoring in the diagnosis of T-cell mediated rejection, transplant practitioners should be aware of the possible clinical implications of the far-from-optimal reproducibility.

Proposed Definitions of T Cell-Mediated Rejection and Tubulointerstitial Inflammation as Clinical Trial Endpoints in Kidney Transplantation

The diagnosis of acute T cell-mediated rejection (aTCMR) after kidney transplantation has considerable relevance for research purposes. Its definition is primarily based on tubulointerstitial inflammation and has changed little over time; aTCMR is therefore a suitable parameter for longitudinal data comparisons. In addition, because aTCMR is managed with antirejection therapies that carry additional risks, anxieties, and costs, it is a clinically meaningful endpoint for studies. This paper reviews the history and classifications of TCMR and characterizes its potential role in clinical trials: a role that largely depends on the nature of the biopsy taken (indication vs protocol), the level of inflammation observed (e.g., borderline changes vs full TCMR), concomitant chronic lesions (chronic active TCMR), and the therapeutic intervention planned. There is ongoing variability—and ambiguity—in clinical monitoring and management of TCMR. More research, to investigate the clinical relevance of borderline changes (especially in protocol biopsies) and effective therapeutic strategies that improve graft survival rates with minimal patient morbidity, is urgently required. The present paper was developed from documentation produced by the European Society for Organ Transplantation (ESOT) as part of a Broad Scientific Advice request that ESOT submitted to the European Medicines Agency for discussion in 2020. This paper proposes to move toward refined definitions of aTCMR and borderline changes to be included as primary endpoints in clinical trials of kidney transplantation.

Acute cellular rejection treatment outcomes stratified by Banff grade in pediatric kidney transplant

INTRODUCTION

There are limited data to guide optimal treatment strategies for acute cellular rejection (ACR) based on Banff grade for pediatric kidney transplant recipients. This report reviews a large pediatric transplant center's experience with ACR.

MATERIALS AND METHODS

A retrospective analysis of pediatric kidney transplant recipients at our center from 2007 to 2014 was performed. Primary outcomes were incidence of graft failure and graft function one year following ACR based on Banff grade and treatment received.

RESULTS

A total of 204 patients were reviewed, of which 65 received rejection treatment with either an oral steroid cycle (n = 16), intravenous steroid pulse (n = 28), or anti-thymocyte globulin (rATG, n = 21). Overall, patients received rATG for treatment of more severe rejection associated with impaired graft function and as a group experienced statistically significant improvements in eGFR over the year following treatment, though most did not regain baseline graft function.

DISCUSSION

Our data suggest that rATG is partially effective in treating ACR, but our study was underpowered to determine the effect of different treatments based on Banff grade. Since there is limited literature to guide clinical treatment of ACR in children, large transplant centers should collaborate to evaluate outcomes and establish evidence-based practice.

Bowman capsulitis predicts poor kidney allograft outcome in T cell-mediated rejection

Acute T cell-mediated rejection (TCMR) is an important cause of renal allograft loss. The Banff classification for tubulointerstitial (type I) rejection is based on the extent of both interstitial inflammation and tubulitis. Lymphocytes may also be present between parietal epithelial cells and Bowman capsules in this setting, which we have termed "capsulitis." We conducted this study to determine the clinical significance of capsulitis. We identified 42 patients from the pathology archives at The University of Chicago with isolated Banff type I TCMR from 2010 to 2015. Patient demographic data, Banff classification, and graft outcome measurements were compared between capsulitis and noncapsulitis groups using Mann-Whitney U test. Capsulitis was present in 26 (62%) and was more frequently seen in Banff IB than in IA TCMR (88% versus 44%, P = .01). Patients with capsulitis had a higher serum creatinine at biopsy (4.6 versus 2.9 mg/dL, P = .04) and were more likely to progress to dialysis (42% versus 13%, P = .06), with fewer recovering their baseline serum creatinine (12% versus 38%, P = .08). Patients with both Banff IA TCMR and capsulitis have clinical outcomes similar to or possibly worse than Banff IB TCMR compared with those with Banff IA and an absence of capsulitis. Capsulitis is an important pathologic parameter in the evaluation of kidney transplant biopsies with potential diagnostic, prognostic, and therapeutic implications in the setting of TCMR.

Efficacy of Acute Cellular Rejection Treatment According to Banff Score in Kidney Transplant Recipients: A Systematic Review

Supplemental digital content is available in the text.

Background

The poor prognosis classically associated with Banff grade 2 acute cell-mediated rejection (CMR) may be due to unrecognized antibody-mediated damage. We thus performed a systematic review of the literature to determine the rate of response to treatment in kidney transplant recipients with pure CMR, stratified by Banff class.

Methods

In addition to a manual search, databases interrogated included Excerpta Medica Database (EMBASE), Medical Literature Analysis and Retrieval System Online (MEDLINE), Evidence-Based Medicine (EBM) databases, Central, PubMed and CINAHL. Studies providing functional and/or histological response rates to the treatment of CMR rejection by Banff class (1997 or more recent) were included.

Results

Among the 746 articles identified, 5 articles were included in the final review. Two studies excluded some, and 2 excluded all features of antibody-mediated rejection, while providing data on functional recovery. The absence of functional recovery was reported in 4% of borderline, 15% for Banff grade 1A and IB pooled, 0% to 25% of Banff grade 1B alone, 11% to 20% of Banff grade 2A, and 38% of Banff grade 2B rejections.

Conclusions

The rate of functional recovery of pure Banff IIA CMR overlapped with that of Banff grade 1 CMR, whereas Banff grade 2B showed worse prognosis. There was important heterogeneity in the definition of response to treatment and paucity of data describing the histological response to treatment stratified by Banff class. There is a pressing need to standardize outcome metrics for the reversibility of rejection in kidney transplant recipients in order to design high-quality trials for novel therapeutic alternatives.

Intimal arteritis in renal allografts: new takes on an old lesion

PURPOSE OF REVIEW

Inflammation of the arterial wall has been recognized as a key element of rejection since the early studies of pathologic changes in transplanted organs. Better elucidation of the mechanisms involved in endothelial injury has brought increasing complexity to the diagnostic classification of this lesion in the context of transplantation, and has affected the clinical management of patients with allograft rejection. Here, we examine how our understanding of the significance of intimal arteritis in renal graft biopsies has evolved in the past decades.

RECENT FINDINGS

Recognition that antidonor antibody may cause intimal arteritis has prompted revision of histologic classifications of transplant rejection. Although molecular signatures/biomarkers are being developed and proposed as new tools for aiding in the identification of cell-mediated and antibody-mediated types of rejection, histological examination is still needed to identify intimal arteritis in allograft biopsies. Outcome studies are contributing to clarify the prognostic significance of intimal arteritis in transplant rejection.

SUMMARY

Intimal arteritis remains an important histologic feature of allograft rejection, which comes in different nuances requiring tailored therapeutic approaches.

Histopathological diagnosis of acute and chronic rejection in pediatric kidney transplantation

ABO-compatible as well as ABO-incompatible kidney transplantation are well established in the pediatric population. There are particularities in the histopathological evaluation of pediatric kidney transplant biopsies as for example the recurrence of certain diseases different from the adult population. Furthermore, the challenging transition of pediatric renal transplant recipients to adulthood is associated with an increased rate of non-adherence triggered rejection episodes. With modern immunosuppressive drugs, T-cell-mediated rejection of renal allografts is well controlled. In contrast, antibody-mediated rejection (AMR) is increasingly recognized as one of the major reasons for allograft loss. However, the 2001 diagnostic Banff criteria for antibody-mediated rejection require further refinement, as the morphological spectrum of AMR expands while effective therapeutic strategies are lacking. For example, endarteritis, which traditionally has been attributed to T-cell-mediated rejection, has recently been shown to be part of the AMR spectrum in some cases. Many findings in transplant renal biopsies are not specific for a certain disease but need consideration of differential diagnoses. To use the term "chronic allograft nephropathy" as a diagnostic entity is no longer appropriate. Therefore, the precise identification of specific diseases is paramount in the assessment of transplant renal biopsies in order to enable tailored therapeutic management.

Emerging Concepts and Controversies in Renal Pathology: C4d-Negative and Arterial Lesions as Manifestations of Antibody-Mediated Transplant Rejection

The consensus classification of antibody-mediated rejection (AMR) of renal allografts developed at the Sixth Banff Conference on Allograft Pathology, in 2001, identified three findings necessary for the diagnosis of active AMR: histologic evidence, antibodies against the graft, and capillary C4d deposition. Morphologic and molecular studies have noted evidence of microvascular injury, which, in the presence of donor-specific antibodies (DSAs) but the absence of C4d deposition, is associated with development of transplant glomerulopathy and graft loss. Recent studies suggest that intimal arteritis may in some cases be a manifestation of DSA-induced graft injury. These newly recognized lesions of AMR have now been incorporated into a revised Banff diagnostic schema.

The severity of acute cellular rejection defined by Banff classification is associated with kidney allograft outcomes

BACKGROUND

It is unclear if the severity or the timing of acute cellular rejection (ACR) defined by Banff classification 2009 is associated with graft survival.

METHODS

Borderline changes, TCMR I (interstitial rejection), and TCMR II/III (vascular rejection) were defined as low, moderate, and high ACR severity, respectively. Approximately 270 patients who had at least one episode of ACR were enrolled, 270 biopsies were chosen which showed the highest ACR severity of each patient and were negative for donor-specific antibodies (DSA), C4d, and microcirculation changes (MC). Six months were used as the cutoff to define early and late ACR; 370 patients without biopsy posttransplantation were recruited in the control group.

RESULTS

Up to 8-year posttransplantation, death-censored graft survival (DCGS) rates of control, borderline, TCMR I, and TCMR II/III groups were 97.6%, 93.3%, 79.6%, and 73.6% (log rank test, P<0.001); the control group had significantly higher DCGS rate than the three ACR groups (each pairwise comparison yields P<0.05). The DCGS rate of late ACR was significantly lower compared with early ACR (63.6% vs. 87.4%, P<0.001). Intimal arteritis (Banff v-lesion) was an independent histologic risk factor correlated with long-term graft loss regardless of the timing of ACR. The v-lesions with minimal or high-grade tubulitis displayed similar graft survival (72.7% vs. 72.9%, P=0.96).

CONCLUSION

All types of ACR affect long-term graft survival. Vascular or late ACR predict poorer graft survival; the extent of tubulointerstitial inflammation (TI) is of no prognostic significance for vascular rejection.

An updated Banff schema for diagnosis of antibody-mediated rejection in renal allografts

PURPOSE OF REVIEW

To introduce the updated Banff schema for antibody-mediated renal allograft rejection and related revisions to definitions within this schema agreed upon during and immediately subsequent to the 2013 Banff Conference on Allograft Pathology.

RECENT FINDINGS

The original Banff schema for diagnosis of acute and chronic, active antibody-mediated rejection (ABMR) in renal allografts, formulated at the 2001 and 2007 Banff Conferences, has been of great assistance to pathologists and clinicians faced with an increasing awareness of the role of donor-specific alloantibodies (DSAs) in producing graft injury. This schema requires histologic (primarily microvascular inflammation and transplant glomerulopathy), immunohistologic (C4d in peritubular capillaries), and serologic (circulating DSA) evidence for a definitive diagnosis of ABMR. Still, like other Banff classifications, the 2001/2007 schema for renal ABMR is a working classification subject to revision based on new data. Increasing evidence for C4d-negative ABMR and antibody-mediated arterial lesions led to the development of a consensus at the 2013 Banff Conference for updating the schema to include these lesions. Definitions and thresholds for glomerulitis and chronic glomerulopathy were also revised to improve interobserver agreement and correlation with clinical, molecular, and serologic data.

SUMMARY

From a consensus reached at the 2013 Banff Conference, an updated schema for diagnosis of acute/active and chronic, active ABMR has been developed that accounts for recent data supporting the existence of C4d-negative ABMR and antibody-mediated intimal arteritis.

Pathologic features of antibody-mediated rejection in renal allografts: an expanding spectrum

PURPOSE OF REVIEW

This review discusses recent findings that are changing and expanding the spectrum of pathologic changes associated with antibodies directed against renal allografts.

RECENT FINDINGS

This review focuses on four lesions: subclinical antibody-mediated rejection (AMR), C4d-negative AMR, intimal arteritis, and arterial intimal fibrosis. A number of studies have identified morphologic lesions of AMR in protocol biopsies of normally functioning renal allografts, particularly in sensitized recipients, that correlate with subsequent development of chronic changes in the graft, including transplant glomerulopathy. These same studies as well as molecular studies of indication biopsies of conventional renal allografts have noted evidence of microvascular injury, which, in the presence of donor-specific antibodies (DSAs) but the absence of C4d deposition in peritubular capillaries, is associated with development of transplant glomerulopathy and graft loss. Finally, recent studies suggest that intimal arteritis, previously felt to represent a lesion of cell-mediated rejection, and bland arterial intimal fibrosis, resembling arteriosclerosis, may in some cases be manifestations of DSA-induced graft injury.

SUMMARY

Incorporation of these newly recognized lesions of AMR into a working diagnostic schema with sufficient sensitivity and specificity to minimize undertreatment and overtreatment of patients is an important challenge currently faced by renal pathologists and transplant clinicians.

Inflammation lesions in kidney transplant biopsies: association with survival is due to the underlying diseases

Assessment of kidney transplant biopsies relies on nonspecific inflammatory lesions: Interstitial infiltrates (i), tubulitis (t) and intimal arteritis (v). We studied the relationship between inflammation and prognosis in biopsies for clinical indications from 314 patients (median follow-up 25 months). We used a modified Banff classification, separately assessing inflammation (i-) in nonscarred (i-Banff), scarred (i-IFTA) and whole cortex (i-total), plus tubulitis and intimal arteritis. In early biopsies (<1 year), i- and t-lesions had no association with graft survival. In late (>1 year) biopsies, all i-scores correlated with progression to failure, due to the association of these infiltrates with progressive diseases: antibody-mediated rejection (ABMR) and glomerulonephritis. Tubulitis in nonscarred areas had no impact on survival. Severe tubulitis including scarred areas (tis3) was associated with worse survival, but reflected polyoma virus nephropathy or ABMR, not T-cell-mediated rejection. Intimal arteritis (v-lesions) had no association with allograft loss in early or late biopsies. In multivariate analysis, outcome was better predicted by the presence of progressive disease than by inflammation. Thus inflammation in late kidney transplants has no inherent prognostic impact, but predicts reduced survival because inflammation indicates actively progressing diseases. The most important predictor of outcome is the diagnosis of a progressive disease.

Microarray analysis of rejection in human kidney transplants using pathogenesis-based transcript sets

Microarrays offer potential for objective diagnosis and insights into pathogenesis of allograft rejection. We used mouse transplants to annotate pathogenesis-based transcript sets (PBTs) that reflect major biologic events in allograft rejection-cytotoxic T-cell infiltration, interferon-gamma effects and parenchymal deterioration. We examined the relationship between PBT expression, histopathologic lesions and clinical diagnoses in 143 consecutive human kidney transplant biopsies for cause. PBTs correlated strongly with one another, indicating that transcriptome disturbances in renal transplants have a stereotyped internal structure. This disturbance was continuous, not dichotomous, across rejection and nonrejection. PBTs correlated with histopathologic lesions and were the highest in biopsies with clinically apparent rejection episodes. Surprisingly, antibody-mediated rejection had changes similar to T-cell mediated rejection. Biopsies lacking PBT disturbances did not have rejection. PBTs suggested that some current Banff histopathology criteria are unreliable, particularly at the cut-off between borderline and rejection. Results were validated in 51 additional biopsies. Thus many transcriptome changes previously described in rejection are features of a large-scale disturbance characteristic of rejection but occurring at lower levels in many forms of injury. PBTs represent a quantitative measure of the inflammatory disturbances in organ transplants, and a new window on the mechanisms of these changes.

Significance of Protocol Biopsies in Living Related Renal Transplant Recipients

INTRODUCTION

Subclinical rejection (SCR) in a normally functioning renal allograft may have an impact on long-term graft outcome. SCR detection is best done by protocol biopsies in clinically normal grafts.

METHODS

We evaluated 20 stable living related renal allografts with protocol biopsies on days 7 and 90 posttransplant. SCR when detected was treated with a 3-day pulse of methylprednisolone therapy. The outcomes of these grafts were compared with 63 other clinically stable renal allografts that did not undergo protocol biopsies.

RESULTS

SCR was observed in 60% of cases. The patients who received antirejection therapy for SCR based on protocol biopsies showed better graft survival and mean serum creatinine values at the end of the follow-up period.

Post-transplant renal tubulitis: the recruitment, differentiation and persistence of intra-epithelial T cells

Tubulitis is used by the Banff protocol as a major criterion to grade acute renal allograft rejection. This review integrates results from in vitro and in vivo studies to develop a chronological model to explain the development and functions of tubular inflammation during the rejection process. Proteoglycan-immobilized chemokines are the primary motivators for the vectorial recruitment of specific immune cell populations from the blood, through the endothelium and interstitial tissues to the renal tubules. After penetration of the basement membrane, T cells encounter TGF-beta that can induce expression of the alphaEbeta7 integrin on proliferating cells. This allows adhesion to E-cadherin on the baso-lateral surfaces of tubular epithelial cells and provides an explanation for the epithelial-specific cytotoxicity observed during acute rejection. Tubular epithelium is also a rich source of IL-15 that can stimulate IL-15 receptor-expressing intratubular CD8+ T cells. This anti-apoptotic microenvironment may explain the long-term persistence of cycling T cells within intact tubules after episodes of acute rejection. These memory-like T cells may have local immunoregulatory properties, including the production of additional TGF-beta, but could also modify normal tubular homeostasis resulting in epithelial to mesenchymal transdifferentiation, tubulointerstitial fibrosis and, ultimately, graft failure.

Acute renal allograft rejection with intimal arteritis: histologic predictors of response to therapy and graft survival

BACKGROUND

Acute renal allograft rejection with intimal arteritis is designated by the widely used Banff 97 classification as type 2A or 2B depending on the extent of arteritis, without regard to interstitial inflammation or tubulitis. We examined whether the distinction between type 2A and 2B is relevant to short- and long-term clinical outcomes, and if outcomes in this subset of acute rejection also are affected by tubulitis, interstitial inflammation, and several additional histologic and clinical parameters.

METHODS

Pathology records were searched to identify cases of acute renal allograft rejection with intimal arteritis diagnosed between January 1985 and September 2000. For each case, the patient's chart was reviewed to determine the response of the rejection episode to therapy, type(s) of therapy given, and length of graft survival. All biopsies were reviewed and Banff acute and chronic indices recorded by a pathologist blinded to these data. Biopsies not showing type 2A or 2B rejection were excluded, as were repeat biopsies from the same patient and cases with recurrent glomerular disease, viral infection, donor-specific antibodies, or more than mild chronic change.

RESULTS

The initial response to anti-rejection therapy was significantly worse in patients with type 2B acute rejection (N = 29) than in those with type 2A (N = 102) by univariate and multivariate analyses, despite more aggressive treatment of type 2B rejection. In a Cox proportional hazards model the hazard ratio for graft failure for 2B versus 2A was 1.9 (P = 0.05), but this was not significant when adjusted for the initial response to therapy. Cases with minimal or mild tubulitis responded better to therapy than those with moderate or severe tubulitis, although graft survival was not significantly affected by the tubulitis score.

CONCLUSIONS

The distinction between types 2A and 2B acute rejection in the Banff 97 classification has significant prognostic value with regard to both short- and long-term clinical outcomes, although the difference in long-term graft survival is mainly related to the initial response to therapy. Reports of biopsies showing type 2A or 2B rejection also should specify the degree of tubulitis present, as the latter may significantly influence the initial response to therapy.

In vitro T cell proliferation from kidney allograft biopsies with unremarkable pathology: new strategies for an old problem

Acute rejection of renal allografts is mediated by infiltrating alloreactive T cells. The goals of this study were to correlate T cell proliferation with rejection and to determine whether T cell proliferation in the absence of rejection would predict future rejection episodes. Toward this, kidney biopsies (n=100) were cultured in the presence of interleukin-2. Cultures were examined at 4, 24, and 48 hr for T cell proliferation. A strong correlation was observed between T cell proliferation at any time point and rejection. There was not a significant correlation between T cell proliferation in biopsies with no rejection and the occurrence of a rejection episode within 2 months. However, T cell proliferation after 4 hr was a better predictor of the occurrence of rejection within 2 months compared with observations after 24 and 48 hr. Therefore, a subgroup of patients with unremarkable biopsies but T cell proliferation may be at risk for rejection and warrant closer observation and possible tailoring of immunosuppression.

International variation in the interpretation of renal transplant biopsies: report of the CERTPAP Project

BACKGROUND

The Banff working formulation of renal transplant pathology is intended to have international application. There remains a need to develop methods to harmonize the application of such grading systems between laboratories. Banff grades do not always permit precise management decisions to be made. Alternative schemes have been devised for the diagnosis of acute rejection, but there have been no independent tests of the different approaches.

METHODS

Sections from 55 renal transplant biopsies were circulated around the laboratories of 22 major transplant units for the Convergence of European Renal Transplant Pathology Assessment Procedures (CERTPAP) Project. Participating pathologists were asked to grade 32 different histological features, without any clinical information. After each circulation of five cases, feedback was provided to participants. Statistical evidence of improvement in interobserver variation was sought. At the end of the study, correlations with the original clinicopathological diagnosis were sought.

RESULTS

Interobserver variation was greater than has previously been reported. For every feature studied, some pathologists consistently under-grade or over-grade. There was relatively little evidence of improvement in interobserver variation as a result of the feedback system. No single feature permitted a reliable diagnosis of acute rejection. Applying the Banff and CCTT schemas to the histological grades showed no clear diagnostic advantage for either system, but a simple computer-based inference network, which combined data from 12 histological features, out performed either approach. Within the "protocol" biopsies studied, long-term survival correlated better with "acute" than with "chronic" histological features.

CONCLUSIONS

These results do not undermine the value of the Banff classification, but they demonstrate a need for caution when translating biopsy results between institutions. It is obvious that evaluation of biopsies in multicenter trials must be done in one center. In the management of individual patients, the need to interpret Banff grades in the light of local experience and clinical information is stressed.