Significance of the Banff borderline biopsy

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.

Mast Cells in Kidney Transplant Biopsies With Borderline T Cell-mediated Rejection and Their Relation to Chronicity

Mast cells are potential contributors to chronic changes in kidney transplants (KTx). Here, the role of mast cells (MCs) in KTx is investigated in patients with minimal inflammatory lesions.

Methods

Fourty-seven KTx biopsies (2009-2018) with borderline pathological evidence for T cell-mediated rejection according to the Banff'17 Update were retrospectively included and corresponding clinical data was collected. Immunohistochemistry for tryptase was performed on formalin-fixed paraffin-embedded sections. Cortical MCs were counted and corrected for area (MC/mm²). Interstitial fibrosis was assessed by Sirius Red staining and quantified using digital image analysis (QuPath).

Results

Increased MC number was correlated to donor age (spearman's r = 0.35, P = 0.022), deceased donor kidneys (mean difference = 0.74, t [32.5] = 2.21, P = 0.035), and delayed graft function (MD = 0.78, t [33.9] = 2.43, P = 0.020). Increased MC number was also correlated to the amount of interstitial fibrosis (r = 0.42, P = 0.003) but did not correlate with transplant function over time (r = -0.14, P = 0.36). Additionally, transplant survival 2 y post-biopsy was not correlated to MC number (mean difference = -0.02, t [15.36] = -0.06, P = 0.96).

Conclusions

MC number in suspicious (borderline) for acute T cell-mediated rejection is correlated to interstitial fibrosis and time post-transplantation, suggesting MCs to be a marker for cumulative burden of tissue injury. There was no association between MCs and transplant function over time or transplant survival 2 y post-biopsy. It remains unclear whether MCs are just a bystander or have pro-inflammatory or anti-inflammatory effects in the KTx with minimal lesions.

Challenges Posed by the Banff Classification: Diagnosis and Treatment of Chronic Active T-Cell-Mediated Rejection

The three primary sites of acute T-cell-mediated rejection (TCMR) in transplanted kidneys are the tubular epithelial cells, interstitium, and the vascular endothelial cells. The pathology of acute lesions is characterized by inflammatory cell infiltration; the final diagnosis suggested by the Banff 2019 classification is guided by grading of tubulitis (the t score), interstitial inflammation (the i score), and endarteritis (the v score). Consistent major issues when using the Banff classification are the etiological classifications of interstitial fibrosis and tubular atrophy (IFTA). From 2015 to 2019, technological advances (i.e., genetic analysis in paraffin sections) increased our understanding of IFTA status in patients with smoldering acute TCMR and the roles played by inflammatory cell infiltration (the i-IFTA score) and tubulitis (the t-IFTA score) in IFTA. These two scores were introduced when establishing the diagnostic criteria for chronic active TCMR. Despite the increase in complexity and the lack of a consensus treatment for chronic active TCMR, the Banff classification may evolve as new techniques (i.e., genetic analysis in paraffin sections and deep learning of renal pathology) are introduced. The Banff conference proceeded as follows. First, lesions were defined. Next, working groups were established to better understand the lesions and to derive better classification methods. Finally, the new Banff classification was developed. This approach will continue to evolve; the Banff classification will become a very useful diagnostic standard. This paper overviews the history of TCMR diagnosis using the Banff classification, and the clinical importance, treatment, and prospects for acute and chronic active TCMR.

Protocol Biopsy After Kidney Transplant: Clinical Application and Efficacy to Detect Allograft Rejection

Background Kidney transplant rejection is a major cause of graft dysfunction and failure. In recent years, there has been increased interest in renal allograft protocol biopsies to allow earlier detection of acute or chronic graft dysfunction or rejection to improve long-term graft survival and reduce graft failure. This study aimed to determine if renal allograft protocol biopsies performed within the first 12 months after transplantation help detect subclinical graft dysfunction or rejection. Methods We performed a retrospective analysis utilizing SUNY Upstate University Hospital data from January 2016 to March 2022 to assess transplant outcomes and biopsies. The study population was divided into two subgroups: non-protocol biopsies and protocol biopsies within the 12 months post-transplant. Results A total of 332 patients met our inclusion criteria and were included in the study. Patients were divided into two subgroups: 135 patients (40.6%) in the protocol biopsy group and 197 patients (59.4%) with non-protocol indication biopsies during the first year after the transplant. The overall number of rejection episodes reported was eight episodes (4.6%) in the protocol biopsy group and 56 episodes (18.3%) in the non-protocol indication biopsy group, which was significantly higher in the non-protocol biopsy group (P=0.001). Antibody-mediated rejection (ABMR) and T-cell-mediated rejection (TCMR) diagnoses were significantly higher in the non-protocol biopsy group (P=0.03 and P=0.03, respectively). We also mentioned a trend in terms of mixed antibody-mediated rejection and T-cell-mediated rejection diagnosis (P=0.07). One year after the rejection, the mean glomerular filtration rate (GFR) was 56.78 mL/min/1.73m² in the protocol biopsy group and 49.14 mL/min/1.73m² in the non-protocol indication biopsy group, and there was no significant difference anymore (P=0.11). The patient survival rate was not significantly higher in the protocol biopsy group compared to the non-protocol indication biopsy group (P=0.42). Conclusion This study suggests that performing protocol biopsies does not significantly benefit rejection rates, graft survival, or renal function within the first 12 months post-transplant. Given these results and the small but non-zero risk of complications associated with protocol biopsies, they should be reserved for those patients at high risk of rejection. It may be more feasible and beneficial to utilize less invasive tests, such as DSA and dd-cfDNA testing, for early diagnosis of a rejection episode.

The Histological Spectrum and Clinical Significance of T Cell-mediated Rejection of Kidney Allografts

T cell-mediated rejection (TCMR) remains a significant cause of long-term kidney allograft loss, either indirectly through induction of donor-specific anti-HLA alloantibodies or directly through chronic active TCMR. Whether found by indication or protocol biopsy, Banff defined acute TCMR should be treated with antirejection therapy and maximized maintenance immunosuppression. Neither isolated interstitial inflammation in the absence of tubulitis nor isolated tubulitis in the absence of interstitial inflammation results in adverse outcomes, and neither requires antirejection treatment. RNA gene expression analysis of biopsy material may supplement conventional histology, especially in ambiguous cases. Lesser degrees of tubular and interstitial inflammation (Banff borderline) may portend adverse outcomes and should be treated when found on an indication biopsy. Borderline lesions on protocol biopsies may resolve spontaneously but require close follow-up if untreated. Following antirejection therapy of acute TCMR, surveillance protocol biopsies should be considered. Minimally invasive blood-borne assays (donor-derived cell-free DNA and gene expression profiling) are being increasingly studied as a means of following stable patients in lieu of biopsy. The clinical benefit and cost-effectiveness require confirmation in randomized controlled trials. Treatment of acute TCMR is not standardized but involves bolus corticosteroids with lymphocyte depleting antibodies for severe, refractory, or relapsing cases. Arteritis may be found with acute TCMR, active antibody-mediated rejection, or mixed rejections and should be treated accordingly. The optimal treatment ofchronic active TCMR is uncertain. Randomized controlled trials are necessary to optimally define therapy.

Borderline Changes in Renal Transplantation: Are We Aware of the Real Impact in Graft Survival?

BACKGROUND

Borderline changes suspicious for acute T-cell-mediated rejection (BC) are frequently seen on biopsy specimens, but their clinical significance and clinical management are still controversial. Our goal was to compare clinical outcomes of kidney transplant recipients with biopsy-proven BC vs acute T-cell-mediated rejection (aTCMR) and the influence of treating BC on graft outcomes.

METHODS

A retrospective cohort study was performed in all kidney transplant recipients with biopsy-proven BC and aTCMR between January 2012 and December 2018, according to Banff 2017 criteria; patients with concomitant antibody-mediated rejection were excluded.

RESULTS

We included 85 patients, 30 with BC (35.3%) and 55 with aTCMR (64.7%). There was no difference between groups regarding demographics, HLA matching and sensitization, immunosuppression, or time of transplant. Treatment with steroids was started in 15 patients with BC (50%) and in all patients with aTCMR, with 4 of the latter additionally receiving thymoglobulin (7.2%). At 1 year post biopsy, overall graft survival was 71%, and despite presenting better estimated glomerular filtration rate (eGFR) at biopsy (33.3 ± 23.4 vs 19.9 ± 13.2 mL/min/1.73 m², P = .008), patients in the BC group presented the same graft survival as the aTCMR group according to Kaplan-Meyer survival curves. When analyzing the BC group (n = 30) and comparing the patients who were treated (n = 15) vs a conservative approach (n = 15), graft survival at 1 year was 87% for treated patients and 73% for nontreated patients (P = .651), with no difference in eGFR for patients with functioning graft. However, at longer follow-up, survival curves showed a trend for better graft survival in treated patients (70.2 ± 9.2 vs 38.4 ± 8.4 months, P = .087).

CONCLUSION

Our study showed that patients with BC did not present better graft survival or graft function at 1 year after biopsy or at follow-up compared with the aTCMR group, despite better eGFR at diagnosis. We found a trend for better graft survival in patients with BC treated with steroids compared with a conservative approach. These results reinforce the importance of borderline changes in graft outcomes and that the decision to treat can influence long-term outcomes.

Three-month course of intragraft transcriptional changes in kidney allografts with early histological minimal injury - a cohort study

The tubulitis with/without interstitial inflammation not meeting criteria for T-cell-mediated rejection (minimal allograft injury) is the most frequent histological findings in early transplant biopsies. The course of transcriptional changes in sequential kidney graft biopsies has not been studied yet. Molecular phenotypes were analyzed using the Molecular Microscope^® Diagnostic System (MMDx) in 46 indication biopsies (median 13 postoperative days) diagnosed as minimal allograft injury and in corresponding follow-up biopsies at 3 months. All 46 patients with minimal injury in early biopsy received steroid pulses. MMDx interpreted indication biopsies as no-rejection in 34/46 (74%), T-cell-mediated rejection (TCMR) in 4/46 (9%), antibody-mediated rejection in 6/46 (13%), and mixed rejection in 2/46 (4%) cases. Follow-up biopsies were interpreted by MMDx in 37/46 (80%) cases as no-rejection, in 4/46 (9%) as TCMR, and in 5/46 (11%) as mixed rejection. Follow-up biopsies showed a decrease in MMDx-assessed acute kidney injury (P = 0.001) and an increase of atrophy-fibrosis (P = 0.002). The most significant predictor of MMDx rejection scores in follow-up biopsies was the tubulitis classifier score in initial biopsies (AUC = 0.84, P = 0.002), confirmed in multivariate binary regression (OR = 16, P = 0.016). Molecular tubulitis score at initial biopsy has the potential to discriminate patients at risk for molecular rejection score at follow-up biopsy.

Clinical and Pathological Analyses of Borderline Changes Cases after Kidney Transplantation

<b><i>Aim:</i></b> We aimed to perform a clinicopathological analysis of cases presenting with borderline changes (BC) after renal transplantation and discuss whether BC might be clinically or pathologically important. <b><i>Materials and Methods:</i></b> BC was diagnosed in 22 renal allograft biopsy specimens obtained from 20 renal transplant recipients between April 2010 and March 2019 after follow-up at the Department of Transplant Surgery, Kidney Center, Toda Chuo General Hospital. <b><i>Results:</i></b> BC was diagnosed at a median of 500 days following transplantation. Among the 22 renal allograft biopsy specimens showing evidence of BC, tubulitis was observed in all specimens. Interstitial inflammation was present in 18 specimens (82%), peritubular capillaritis in 14 (64%), interstitial fibrosis (ci) and tubular atrophy (ct) in 4 (18%), and C4d deposition in the peritubular capillary was present in 6 specimens (27%). Glomerulitis and intimal arteritis were not observed. There was no renal graft loss during the observation period, but deterioration of renal allograft function after biopsy occurred in 9 patients (45%). <b><i>Conclusions:</i></b> In BC, tubulitis and interstitial inflammation were the main constituents. Because glomerulitis was not observed in our study, we suspect that BC contributes to acute T-cell-mediated rejection. Although BC did not lead to renal graft loss, renal graft function deterioration was seen in nearly half of the patients after the renal graft biopsy. We conclude that BC is important clinically and pathologically and needs to be monitored and treated appropriately.

Treatment of borderline infiltrates with minimal inflammation in kidney transplant recipients has no effect on allograft or patient outcomes

In 2005, the Banff committee expanded the "borderline changes" category to include lesions with minimal (<10%) inflammation: "i0" borderline infiltrates. Clinical significance and optimal treatment of i0 borderline infiltrates are not known. Data suggest that i0 borderline infiltrates may have a more favorable prognosis than borderline infiltrates with higher grades of interstitial inflammation. In this single-center, retrospective, observational study, we assessed 90 renal transplant recipients with i0 borderline infiltrates on biopsies indicated for graft dysfunction. We studied the impact of treatment with corticosteroids on allograft function, allograft survival, and patient survival. We found no differences between treated and untreated groups with respect to eGFR at 4 weeks and 6 months after biopsy. Follow-up biopsies, available in 67% of patients, were negative for rejection in almost half of all cases, regardless of treatment status. The frequencies of persistent borderline infiltrates (38%) and higher-grade T cell-mediated rejection (1A or greater, 14%) on follow-up biopsies were similar between the two groups. There were no differences in rejection-free allograft survival, death-censored graft failure, or patient mortality among treated vs non-treated i0 borderline patients. Our findings suggest that the natural history of i0 borderline infiltrates, in relatively low immunologic risk patients, is not affected by corticosteroid treatment.

Early subclinical tubulitis and interstitial inflammation in kidney transplantation have adverse clinical implications

This prospective observational cohort study compared the impact of subclinical tubulitis with or without interstitial inflammation to interstitial inflammation alone and to no inflammation in early post kidney transplant biopsies. A study cohort of 415 patients (living and deceased donor recipients) was divided into three groups on the basis of their three-month biopsy: 149 patients with No Inflammation (NI), 83 patients with Isolated Interstitial Inflammation (IIF), and 183 patients with Tubulitis [(with or without interstitial inflammation) (TIF) but not meeting criteria for Banff IA]. TIF was further divided into 56 patients with tubulitis without interstitial inflammation (TIF0) and 127 patients with tubulitis alongside interstitial inflammation (TIF1). TIF was significantly associated with higher incidence of subsequent T-cell mediated rejection (clinical or subclinical) at one year compared to IIF (31% vs 15%) and NI (31% vs 17%). Chronicity on one-year biopsy was significantly higher in TIF compared to IIF (22% vs 11%) and NI (22% vs 7%). De novo donor-specific antibody development was significantly higher in TIF compared to NI (6% vs 0.7%). Tubulitis subgroups (TIF0 and TIF1) revealed comparable effects on de novo donor-specific antibody and interstitial fibrosis/tubular atrophy development. However, tubulitis with interstitial inflammation had a significantly higher incidence of subsequent rejection and posed an increased hazard for the composite end point (subsequent acute rejection and death censored graft loss) compared to other groups [adjusted hazard 2.1 (95% confidence interval 1.2-3.5)]. Thus, subclinical tubulitis is a marker of adverse immunological events, but tubulitis with interstitial inflammation has a worse prognosis. Hence, the Banff 1997 (TIF1) and Banff 2005 classifications (TIF) for borderline change may have different implications.

The clinical and pathological significance of borderline T cell-mediated rejection

The pathological diagnosis of borderline rejection (BL-R) denotes possible T cell-mediated rejection (TCMR), but its clinical significance is uncertain. This single-center, cross-sectional cohort study compared the functional and histological outcomes of consecutive BL-R diagnoses (n = 146) against normal controls (n = 826) and acute TCMR (n = 55) from 551 renal transplant recipients. BL-R was associated with the following: contemporaneous renal dysfunction, acute tubular necrosis, and chronic tubular atrophy (P < .001); progressive tubular injury with fibrosis by longitudinal sequential histology (45.3% at 1 year); increased subsequent acute rejection (39.4%), allograft failure (P < .001), and patient mortality (P = .007). BL-R detected by biopsy indicated for impaired function was followed by suboptimal functional recovery (46.3%), persistent inflammation (27.2%), and acute rejection episodes (50.0%) despite antirejection treatment in 83.3%. By 1 year after BL-R, the incidence of new-onset microvascular inflammation (9.3%), C4d staining (22.3%), transplant glomerulopathy (13.3%), and de novo donor-specific antibodies (31.5%) exceeded normal controls (P < .05-.001). BL-R inflammation in protocol biopsy persisted in 28.0% and progressed to acute rejection in 32.6%; however, it resolved in 61.6% of the untreated cases. In summary, BL-R is a heterogeneous diagnostic grouping, ranging from mild inconsequential inflammation to clinically significant TCMR, which is capable of immune-mediated tubular injury resulting in inferior functional, immunological, and histological consequences.

[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.

Borderline Changes on Dysfunctional Renal Allograft Biopsies: Clinical Relevance in a Living Related Renal Transplant Setting

OBJECTIVES

Our aim was to determine the clinical significance of borderline lymphocytic infiltrates on indicated renal allograft biopsies in a living related renal transplant setting.

MATERIALS AND METHODS

The study was conducted at the histopathology department of Sindh Institute of Urology and Transplantation. A retrospective review of 421 renal transplant patients was conducted from October 2007 to September 2008 to identify patients in whom a histologic diagnosis of borderline changes was made on dysfunctional renal allograft biopsies. Demographic, clinical, and laboratory data; biopsy findings; treatments given; and responses to treatment were collected and analyzed. Standard biopsy indications determined the need for graft biopsies. Biopsies were reported according to Banff criteria.

RESULTS

Mean age was 26.92 ± 9.14 years (range, 10-45) for recipients and 38.46 ± 9.16 years (range, 19-50) for donors. Males were predominant among recipients (84.6% vs 15.4%), and females were predominant among donors (57.7% vs 42.3%). The best serum creatinine levels were 1.79 ± 1.15 mg/dL (range, 0.83-6.12). These were achieved after a median of 3 days (interquartile range, 2-7.25). Dysfunctional biopsies exhibiting borderline infiltrates were performed at a median duration of 5.5 days (interquartile range, 3-14.25). Mean serum creatinine at the time of biopsy was 2.34 ± 1.43 mg/dL (range, 1.25-8.25). The biopsies showed borderline cellular infiltrates (interstitial inflammation 1 [i1] and tubulitis 1 and [t1] lesions). All recipients except one received antirejection treatment (antithymocyte globulin, n = 5; escalation of mycophenolate mofetil dosage, n = 1; pulse steroids, n = 19); all recipients responded with a decline in serum creatinine toward baseline, with a mean serum creatinine of 1.31 ± 0.42 mg/dL (range, 0.40-2.71). This response was achieved at a median duration of 9.73 ± 5.32 days (range, 1-23) after starting treatment.

CONCLUSIONS

The borderline cellular infiltrates on dysfunctional renal allograft biopsies signify evolving phases of acute cellular rejection. These infiltrates responded favorably to antirejection treatment in our setting.

Using Molecular Phenotyping to Guide Improvements in the Histologic Diagnosis of T Cell-Mediated Rejection

Recognition that some lesions typical of T cell-mediated rejection (TCMR) also occur in antibody-mediated rejection requires revision of the histologic TCMR definition. To guide this process, we assessed the relative importance of various lesions and the performance of new histology diagnostic algorithms, using molecular TCMR scores as histology-independent estimates of true TCMR. In 703 indication biopsies, random forest analysis and logistic regression indicated that interstitial infiltrate (i-lesions) and tubulitis (t-lesions) were the key histologic predictors of molecular TCMR, with arteritis (v-lesions) having less importance. Histology predicted molecular TCMR more accurately when diagnoses were assigned by strictly applying the Banff rules to the lesion scores and redefining isolated v-lesion TCMR. This improved prediction from area under the curve (AUC) 0.70 with existing rules to AUC 0.80. Further improvements were achieved by introducing more categories to reflect inflammation (AUC 0.84), by summing the lesion scores (AUC 0.85) and by logistic regression (AUC 0.90). We concluded that histologic assessment of TCMR can be improved by placing more emphasis on i- and t-lesions and incorporating new algorithms for diagnosis. Nevertheless, some discrepancies between histologic and molecular diagnoses persist, partially due to the inherent nonspecificity of i- and t-lesions, and molecular methods will be required to help resolve these cases.

Chronic allograft injury by subclinical borderline change: evidence from serial protocol biopsies in kidney transplantation

Purpose

This study investigated the impact of subclinical borderline changes on the development of chronic allograft injury in patients using a modern immunosuppression protocol.

Methods

Seventy patients with stable renal allograft function and who underwent protocol biopsies at implantation, 10 days and 1 year after transplantation were included and classified based on biopsy findings at day 10. The no rejection (NR) group included 33 patients with no acute rejection. The treatment (Tx) group included 21 patients with borderline changes following steroid pulse therapy, and the nontreatment (NTx) group included 16 patients with borderline changes nontreated.

Results

The Banff Chronicity Score (BChS) and modified BChS (MBChS) were not different among the three groups at implantation (P = 0.48) or on day 10 (P = 0.96). Surprisingly, the NTx group had more prominent chronic scores at the 1-year biopsy, including BChS (3.07 ± 1.33, P = 0.005) and MBChS (3.14 ± 1.41, P = 0.008) than those in the Tx and NR group, and deterioration of BChS was more noticeable in the NTx group (P = 0.037), although renal function was stable (P = 0.66). No difference in chronic injury scores was observed between the Tx and NR groups at the 1-year biopsy.

Conclusion

Subclinical borderline changes can be a risk factor for chronic allograft injury and should be considered for antirejection therapy.

The nature of biopsies with "borderline rejection" and prospects for eliminating this category

In kidney transplantation, many inflamed biopsies with changes insufficient to be called T-cell-mediated rejection (TCMR) are labeled "borderline", leaving management uncertain. This study examined the nature of borderline biopsies as a step toward eventual elimination of this category. We compared 40 borderline, 35 TCMR and 116 nonrejection biopsies. TCMR biopsies had more inflammation than borderline but similar degrees of tubulitis and scarring. Surprisingly, recovery of function after biopsy was similar in all categories, indicating that response to treatment is unreliable for defining TCMR. We studied the molecular changes in TCMR, borderline and nonrejection using microarrays, measuring four published features: T-cell burden; a rejection classifier; a canonical TCMR classifier; and risk score. These reassigned borderline biopsies as TCMR-like 13/40 (33%) or nonrejection-like 27/40 (67%). A major reason that histology diagnosed molecularly defined TCMR as borderline was atrophy-scarring, which interfered with assessment of inflammation and tubulitis. Decision tree analysis showed that i-total >27% and tubulitis extent >3% match the molecular diagnosis of TCMR in 85% of cases. In summary, most cases designated borderline by histopathology are found to be nonrejection by molecular phenotyping. Both molecular measurements and histopathology offer opportunities for more precise assignment of these cases after clinical validation.

Identification of lesions indicating rejection in kidney transplant biopsies: tubulitis is severely under-detected by conventional microscopy

BACKGROUND

In the current international Banff classification of kidney transplant rejection, tubulitis and intimal arteritis are regarded as the key histological features of acute rejection. Grade 1 tubulitis can sometimes be seen in biopsies that do not represent acute rejection; but in the case of intimal arteritis, just one lymphocyte can justify anti-rejection treatment. Our aim was to audit reliability and accuracy of recognizing tubulitis and intimal arteritis using the approach recommended by the Banff classification and correlate any discrepancies with subsequent graft function.

METHODS

This is a retrospective review of all kidney transplant biopsies reported as negative for rejection from 1 January 2009 to 31 December 2009 to assess the presence or absence of occult tubulitis and arteritis. Lymphocytes were immunostained with CD3, using Periodic Acid Schiff as a counterstain. Sections were reviewed to detect missed intimal arteritis and tubulitis. Discrepancies between the report and the immunostain results were analysed by biopsy type and broken down by the reporting pathologist. The graft function of any patient with missed lesions was checked to test for adverse impact on the patient.

RESULTS

'Missed' tubulitis was found in 68% of biopsies, but only two such cases subsequently developed biopsy-proven acute rejection. Only one case of missed intimal arteritis was found (1%) and the subsequent clinical course suggested that this was probably early rejection. There was no significant difference between the reporting pathologists.

CONCLUSIONS

We conclude that tubulitis is missed very frequently, but the Banff classification seems to be 'calibrated' to allow for this and it does not seriously affect the identification of clinically significant acute rejection. Immunostaining is therefore not indicated in routine practice because (by Banff criteria) it would result in over-diagnosis of rejection. Intimal arteritis can indicate acute rejection even if extremely mild.

Rejection and function and chronic allograft dysfunction

Despite the impressive reduction in early acute rejection rates over the past decades, chronic allograft dysfunction remains a key issue after renal transplantation. A number of factors, such as the quality of the original organ, ischemia/reperfusion injury, and/or (treated) acute rejection, will adversely affect renal structure, causing early (but often mild) tubular atrophy and interstitial fibrosis. It remains, however, controversial whether subclinical acute rejection or borderline changes imply a different functional prognosis with longer times of follow-up, if cases with late clinical acute rejection, inadequate dosing, and/or incompliance with drug prescription are excluded. Serum creatinine and immunosuppressant trough levels constitute the current standard biomarkers for assessing and renal function and systemic drug exposure, respectively. Serum creatinine is a notoriously unreliable marker for the glomerular filtration rate; changes in creatinine concentration occur late in disease progression and do not accurately represent the ongoing underlying renal damage. Trough level monitoring without information on the patient's absorption profile or the related systemic drug exposure is equally unreliable for guiding initial calcineurin inhibitor dosing or for controlling systemic drug exposure while tapering. Until more sophisticated biomarkers to guide clinical immunosupprression become available, protocol biopsies may prove to be most useful in patients with an increased risk for (late) acute rejection.

Borderline rejection after renal transplantation--to treat or not to treat

According to the Banff classification of renal allograft pathology, the category borderline changes defines changes insufficient for a diagnosis of acute rejection. The relationship between borderline changes and acute renal allograft rejection still remains unclear. The appropriate clinical management for patients showing such changes is controversial. One possible interpretation of the high incidence of subacute tubulitis is that these changes in the absence of graft dysfunction are of no consequence and that treatment with intensified immunosuppression is unnecessary and perhaps harmful. Another view, consistent with the high incidence of CAN in late protocol biopsy studies, is that immunosuppression has become so powerful, that rejection may not even be manifested by a rising serum creatinine. Borderline changes should be used as part of an algorithm, but not as the only criterion, for therapeutic decision making. Based on the weak evidence of existing studies, in our patients with clinical borderline rejection, we have to weigh the individual immunological risk against the potential side effects of increased immunosuppression. Even in the knowledge that a majority of patients with borderline infiltrates will not progress into rejection, in many transplant centers, borderline rejection is treated with additional steroids or augmentation of maintenance immunosuppression.

Diagnosing rejection in renal transplants: a comparison of molecular- and histopathology-based approaches

The transcriptome has considerable potential for improving biopsy diagnoses. However, to realize this potential the relationship between the molecular phenotype of disease and histopathology must be established. We assessed 186 consecutive clinically indicated kidney transplant biopsies using microarrays, and built a classifier to distinguish rejection from nonrejection using predictive analysis of microarrays (PAM). Most genes selected by PAM were interferon-gamma-inducible or cytotoxic T-cell associated, for example, CXCL9, CXCL11, GBP1 and INDO. We then compared the PAM diagnoses to those from histopathology, which are based on the Banff diagnostic criteria. Disagreement occurred in approximately 20% of diagnoses, principally because of idiosyncratic limitations in the histopathology scoring system. The problematic diagnosis of 'borderline rejection' was resolved by PAM into two distinct classes, rejection and nonrejection. The diagnostic discrepancies between Banff and PAM in these cases were largely due to the Banff system's requirement for a tubulitis threshold in defining rejection. By examining the discrepancies between gene expression and histopathology, we provide external validation of the main features of the histopathology diagnostic criteria (the Banff consensus system), recommend improvements and outline a pathway for introducing molecular measurements.

Intragraft levels of Foxp3 mRNA predict progression in renal transplants with borderline change

The optimal therapeutic management of borderline lymphocytic infiltrates in renal allografts, described by Banff criteria, is unknown, largely because of the inability to predict clinical outcome in these cases. For determination of molecular factors that may predict outcome in cases of borderline change histology, mRNA levels of Foxp3, Granzyme B, IFN-gamma, IL-23, and RORgammat were measured in renal tissue from 46 untreated patients. Twenty-five patients were considered "nonprogressive," defined by a serum creatinine that remained <110% of baseline during the 40 d after biopsy. Twenty-one patients were considered "progressive," defined by an increase in serum creatinine >110% from baseline and by repeat histologic examination within 40 d showing progression toward acute rejection. Only Foxp3 mRNA levels were significantly higher in nonprogressors than in progressors (P = 0.001). Analysis of receiver operating characteristic curves demonstrated that the outcome for patients with biopsies showing borderline change could be predicted with 90% sensitivity and 79.1% specificity using the optimal Foxp3 mRNA cutoff value. Our findings suggest that the measurement of Foxp3 mRNA offers a means of improving prediction of outcome of borderline change.

Immunosuppressive drug therapy and subclinical acute renal allograft rejection: impact and effect

The incidence of subclinical acute rejection (SCAR) varies between 5% and 15% with current maintenance immunosuppressive drug regimens. Despite many similarities between SCAR and clinical acute rejection exist, the inflammatory activated cell infiltrates are not completely identical while graft cytokine profiles and counteractive immune responses are characterized by subtle differences that could explain why SCAR is not accompanied by immediate graft dysfunction. Evidence that SCAR contributes to chronic allograft damage (interstitial fibrosis and tubular atrophy) and negatively affects graft outcome is counterbalanced by the scarcity of controlled data proving the beneficial effect of SCAR treatment. The development of sensitive and specific noninvasive methods to monitor the immune status of the graft by using mRNA determinations, gene expression analysis (microarrays), proteomic analysis, and magnetic resonance spectroscopy, can help to ultimately replace protocol biopsies and also contribute to the further unraveling of the complex underlying immunological mechanisms responsible for SCAR. The latter would enable clinicians to preemptively make strategic adjustments to immunosuppressive therapy in an attempt to further improve renal allograft survival and clinical care of the transplant patient.

Chronic allograft nephropathy

PURPOSE OF REVIEW

Despite dramatic declines in acute rejection and early graft failure, long-term outcomes after kidney transplantation have improved little during the past 25 years. Most late allograft failure is attributed to chronic allograft nephropathy, but this is a clinicopathological description and not a diagnosis, and its pathogenesis and treatment are largely unknown.

RECENT FINDINGS

Recent studies suggest that acute rejection during the first few months, and calcineurin inhibitor toxicity thereafter, may both contribute to chronic allograft nephropathy. There is also accumulating evidence that injury from antibody-mediated rejection may play an important pathogenic role in at least some patients with chronic allograft nephropathy, particularly those with transplant glomerulopathy. Therapeutic measures, including protocols to reduce calcineurin inhibitor exposure, remain largely unproven.

SUMMARY

Understanding why so many kidney allografts fail, despite effective preventive measures for early acute rejection, is one of the most important areas of research in kidney transplantation today.

SWOT analysis of Banff: strengths, weaknesses, opportunities and threats of the international Banff consensus process and classification system for renal allograft pathology

The Banff process defined the diagnostic histologic lesions for renal allograft rejection and created a standardized classification system where none had existed. By correcting this deficit the process had universal impact on clinical practice and clinical and basic research. All trials of new drugs since the early 1990s benefited, because the Banff classification of lesions permitted the end point of biopsy-proven rejection. The Banff process has strengths, weaknesses, opportunities and threats (SWOT). The strength is its self-organizing group structure to create consensus. Consensus does not mean correctness: defining consensus is essential if a widely held view is to be proved wrong. The weaknesses of the Banff process are the absence of an independent external standard to test the classification; and its almost exclusive reliance on histopathology, which has inherent limitations in intra- and interobserver reproducibility, particularly at the interface between borderline and rejection, is exactly where clinicians demand precision. The opportunity lies in the new technology such as transcriptomics, which can form an external standard and can be incorporated into a new classification combining the elegance of histopathology and the objectivity of transcriptomics. The threat is the degree to which the renal transplant community will participate in and support this process.

To Biopsy or Not to Biopsy? Should We Screen the Histology of Stable Renal Grafts?

Chronic allograft dysfunction is currently the main cause of late allograft failure. Recent encouraging evidence suggests that it may be possible to delay the development of graft damages if adequate management is initiated early in the course of the disease. These observations have renewed interest in the performance of protocol biopsies as routine follow-up procedure for the screening of renal transplants. In the present review, we summarize the available data from the literature to determine the pros and cons of protocol renal allograft biopsies. On the basis of this evidence, we discuss the ethical concerns raised by this procedure.

Renal pathology in the pediatric transplant patient

Renal transplantation is a therapeutic goal for children with advanced chronic kidney disease. There are many causes of renal dysfunction in children with allografts--the transplanted kidney can develop a variety of morphologic alterations leading to dysfunction. Evaluation of the kidney biopsy is one of the best methods of determining the cause of graft dysfunction. Rejection is a major cause of renal allograft failure in children. The morphologic hallmarks of acute antibody-mediated and cell-mediated rejection and chronic allograft nephropathy have been codified in classification strategies that are useful in adults and children. Viral infection and Epstein-Barr virus-driven posttransplant lymphoproliferative disease also occur in the pediatric transplanted kidney. Drug toxicity from immunosuppressive agents also causes characteristic morphologic alterations in the renal allograft. As the survival of pediatric heart and liver transplant patients improves, the incidence of immunosuppression therapy-related disease in the native kidney in these patients will likely become more important clinically. In addition to renal lesions related to the allograft state, glomerular disease can recur or occur de novo in renal allografts. Here, we describe the pathology of the more common morphologic lesions in kidneys of children with a renal allograft.

The significance of subclinical rejection and the value of protocol biopsies

Subclinical rejection (SCR) is diagnosed by protocol histology with a maximal prevalence occurring early after transplantation, falling to low levels by 1 year. Needle-core biopsy is safe, and the histology obtained fairly reflects subclinical immune activity. Several studies have consistently shown that SCR is associated with chronic tubulointerstitial damage, subsequent renal dysfunction and reduced graft survival. SCR is effectively treated by pulse corticosteroid therapy, although increased baseline immunosuppression may be necessary. A single randomized clinical trial of biopsy and corticosteroid therapy demonstrated significantly improved early structural and functional outcomes, and a (nonsignificant) 17% risk reduction in 4-year graft survival. Three possible approaches include: no protocol biopsies (usually accompanied by powerful immunosuppression); biopsies only in high-risk recipients (who may be difficult to reliably predict) or universal screening protocol biopsy (comprehensive but limited by cost and resource utilization). The appropriate screening methodology for a transplant unit is both a clinical and an economic decision; influenced by the SCR prevalence and potential gains of treatment, against costs and resource utilization. Further trials to quantify the cost-benefit balance in a typical, heterogeneous recipient population using modern immunosuppression are required.

Renal allograft biopsies with borderline changes: predictive factors of clinical outcome

The clinical outcome and appropriate management for patients showing 'borderline changes' on allograft biopsy after renal transplantation is still controversial. In an attempt to identify predictive factors of clinical outcome of patients with such lesions, we reviewed the clinical course of 91 patients with borderline changes. Multivariate analysis revealed significant and independent effects of histological stage (i + t < or = or > 2) and time to borderline changes (< or = or > 3 months after transplant) on serum creatinine levels at 1 year from borderline changes episodes (respectively, p = 0.04 and p = 0.02) and only a significant effect of time to borderline changes on serum creatinine levels at 2 years (p = 0.005). Renal function at 1 year and 2 years as 5- and 8-year graft survival were not significantly different in the group of patients treated with antirejection therapy (T group, n = 49) compared with the untreated group (UT group, n = 42). This study strongly suggests that borderline changes with histological score (i + t) > 2 and late episodes of borderline changes should be considered to be of poor prognosis.

Indicators of Acute Rejection on Tc-99m DTPA Renal Scintigraphy

INTRODUCTION

Specific criteria for diagnosing an acute rejection episode (ARE) are not present on renal scintigraphy. However, a deterioration in renal function observed on serial imaging is suggestive of an ARE during the early posttransplantation period. In this study, we evaluated Tc-99m DTPA renal scintigraphy findings among patients with renal allograft dysfunction. The aim was to define criteria for ARE on a single imaging study alone.

MATERIALS AND METHODS

This study included 82 patients with renal allograft dysfunction, each of whom had a specific biopsy-proven pathology. From the background-corrected Tc-99m DTPA renal time-activity curves, the following parameters were computed: the ratio of counts at peak perfusion to that at plateau (P:PL) and the ratio of counts at peak perfusion to that at peak uptake (P:U). The images were inspected visually for excretion patterns and other morphological changes.

RESULTS

A specific renogram pattern, that is an increase in perfusion to uptake ratio together with a nearly flat uptake curve and preserved peak/plateau pattern, was observed in 67% of low-grade AREs. In contrast, a flat uptake curve usually occurred together with a loss of peak/plateau pattern in a high-grade ARE. The findings that were highly specific for ARE on visual inspection were little or no collecting system activity, pelvic hypoactivity, and indistinctness of the corticomedullary junction.

CONCLUSIONS

Our results indicate that in low-grade ARE, there is decreased filtration relative to perfusion as evidenced by a decrease in the perfusion-to-uptake ratio with loss of a peak/plateau pattern. A hypoactive pelvis with little activity in the collecting systems may be due to edema in the renal interstitium and pelvicalyceal structures.

Predictive factors of acute rejection after early cyclosporine withdrawal in renal transplant recipients who receive mycophenolate mofetil: results from a prospective, randomized trial

The aim of this randomized, open-labeled trial was to compare the incidence of acute rejection after an early (3 mo posttransplantation) withdrawal of cyclosporine (CsA) or mycophenolate mofetil (MMF) in renal transplantation. Among 218 eligible recipients, 108 nonsensitized, rejection-free patients who were under a triple drug regimen (CsA-MMF-prednisone) and had received a first kidney from a deceased donor were enrolled. At 3 mo after graft, they were gradually withdrawn from CsA (MMF group, n = 54) or MMF (CsA group, n = 54). A graft biopsy and a pharmacokinetic study of CsA and mycophenolic acid were systematically performed before the randomization. At 1 yr, graft and patient survival rates were 100% in each group. Renal function was improved in the MMF group compared with the CsA group (Cockcroft calculated clearance 64.7 +/- 18.7 versus 56.5 +/- 18.0 ml/min; P = 0.023). However, the probability of acute rejection was higher in the MMF group (18.5 versus 5.6%; P = 0.045). The 10 patients who developed acute rejection after CsA withdrawal had a significantly higher incidence of borderline changes on the randomization biopsy than the 44 rejection-free patients (five of 10 versus eight of 44; P = 0.034), and they displayed a lower area under the curve of mycophenolic acid (43 +/- 9 versus 58 +/- 22 mg/h per L; P = 0.045). Multivariate analysis confirmed that borderline changes and area under the curve of mycophenolic acid were significant risk factors of acute rejection after CsA discontinuation. It is concluded that a systematic graft biopsy and a pharmacokinetic study of mycophenolic acid are needed to reduce the risk for acute rejection after CsA withdrawal.

Clinical significance of an early protocol biopsy in living-donor renal transplantation: ten-year experience at a single center

We report here our 10-year experience of a biopsy performed at day 14 after transplantation in 304 patients with stable graft function. The factors that may have influenced subclinical rejection were analyzed according to histology. The incidence of subclinical rejection was 13.2%. Addition of mycophenolate mofetile (MMF) as a primary immunosuppressant significantly decreased the incidence of subclinical rejection compared with patients without such treatment (odds ratio, 0.23; p < 0.05). On the other hand, HLA-DR antigen mismatch (odds ratio, 2.39) and unrelated donor (odds ratio, 2.10) were also significantly associated with decreased subclinical rejection (p < 0.05). The incidence of acute rejection in patients with normal findings was lower than in those with borderline changes or subclinical rejection (0.23 +/- 0.05 vs. 0.48 +/- 0.07 and 0.60 +/- 0.11, respectively; p < 0.05). The graft survival rates in patients with subclinical rejection were lower than in patients with normal or borderline changes at 1 (88.4% vs. 97.9% and 99.1%; p < 0.05), 5 (77.8% vs. 96.2% and 95.9%; p < 0.05) and 10 (62.3% vs. 96.2% and 93.7%; p < 0.05) years. Thus, a protocol biopsy performed on day 14 after transplantation is useful for predicting graft survival. Triple therapy including MMF, related donor and HLA-DR antigen match are important factors for reducing subclinical rejection in living-donor renal transplantation.

Natural History, Risk Factors, and Impact of Subclinical Rejection in Kidney Transplantation

BACKGROUND

Subclinical rejection (SCR) is defined as histologically proven acute rejection in the absence of immediate functional deterioration.

METHODS

We evaluated the impact of SCR in 961 prospective protocol kidney biopsies from diabetic recipients of a kidney-pancreas transplant (n=119) and one kidney transplant alone taken regularly up to 10 years after transplantation.

RESULTS

SCR was present in 60.8%, 45.7%, 25.8%, and 17.7% of biopsies at 1, 3, 12, and greater than 12 months after transplantation. Banff scores for acute interstitial inflammation and tubulitis declined exponentially with time. SCR was predicted by prior acute cellular rejection and type of immunosuppressive therapy (P<0.05-0.001). Tacrolimus reduced interstitial infiltration (P<0.001), whereas mycophenolate reduced tubulitis (P<0.05), and the combination effectively eliminated SCR (P<0.001). Persistent SCR of less than 2 years duration on sequential biopsies occurred in 29.2% of patients and was associated with prior acute interstitial rejection (P<0.001) and requirement for antilymphocyte therapy (P<0.05). It resolved by 0.49 +/- 0.33 years and resulted in higher grades of chronic allograft nephropathy (CAN, P<0.05). True chronic rejection, defined as persistent SCR of 2 years or more duration and implying continuous immunologic activation was found in only 5.8% of patients. The presence of SCR increased chronic interstitial fibrosis, tubular atrophy, and CAN scores on subsequent biopsies (P<0.05-0.001). SCR preceded and was correlated with CAN (P<0.001) on sequential analysis.

CONCLUSIONS

Histologic evidence of acute rejection in the absence of clinical suspicion resulted in significant tubulointerstitial damage to transplanted kidneys and contributed to CAN.

Borderline changes in the banff schema: rejection or no rejection?

The relationship between acute renal allograft rejection and histopathologic biopsy alterations recognized by the Banff Schema as "borderline changes" is not clear. Some evidence supports the contention that about one third of patients with borderline infiltrates and clinical evidence of graft dysfunction do indeed have acute rejection, which, if left untreated, progresses to a histologically more advanced stage of rejection. Several investigators recognize that not all patients with mild tubulitis respond clinically to antirejection therapy; a significant number of these biopsy specimens display additional histological alterations. The most common concurrent lesions are chronic allograft nephropathy, arteriolar lesions consistent with calcineurin inhibitor toxicity, acute tubular necrosis, and obstructive nephropathy. Management of patients with borderline changes must tightly correlate the pathologic features and the clinical information.

Histological evaluation of renal allograft protocol biopsies in the early period and 1 year after transplantation

We histologically evaluated protocol biopsy specimens of renal allografts obtained in the early period and 1 year after transplantation. The patients were divided into those with at least one history of acute rejection (AR group) and no history of rejection (NAR group), and the histopathological features in the two groups were compared. A total of 45 early protocol biopsy specimens were obtained from 40 patients, and 31 1-year biopsy specimens were obtained from 30 patients. Acute rejection (AR) or borderline change was observed in the early protocol biopsy specimens from 19 (45.2%) cases. AR or borderline change was observed in 12 of 19 (63.2%) in the AR group, and in 7/26 cases (26.9%) in the NAR group. The incidence of AR or borderline change in the AR group was higher than in the NAR group. Toxic tubulopathy was found in the early protocol biopsy in 16 cases (35.6%). The 1-year biopsies tended to reveal more complicated findings. Chronic rejection (CR) was seen in 8/16 cases (50.0%) in the AR group, and it was more frequent than NAR group (two cases, 13.3%). In conclusion, the incidences of both AR and CR were higher in the cases with a previous episode of AR. The early protocol biopsy was useful in screening for subclinical AR and toxic tubulopathy. The 1-year biopsy was useful for evaluating various types of chronic graft damage. We expect that adequate treatment based on protocol biopsy findings in each patient will lead to better graft survival.

Comparisons of clinicopathological correlations between immediate and slow graft function in renal transplant recipients

The functional recovery state of renal transplants can be divided into three types: immediate graft function (IGF), slow graft function (SGF) and delayed graft function (DGF). In contrast to the well-known clinical outcomes for IGF and DGF, the pathological findings and clinical outcomes of SGF are undetermined. This study evaluated possible clinicopathological correlations in 237 patients with SGF compared with patients with IGF. IGF and SGF were defined by serum creatinine levels (IGF < 1.2 mg/day l; SGF: >/=1.2 mg/dL) at day 14 after renal transplantation. Graft biopsy was performed on this day, and pathological classification was performed using the Banff schema. The SGF group of patients (n = 121) showed higher rates of cadaver donors and male recipients than the IGF group (n = 116), but there were no significant differences in recipient or donor age, numbers of HLA mismatches, types of immunosuppressant or follow-up periods between two groups. The SGF group showed higher serum creatinine levels at discharge, and a higher incidence of acute rejection than the IGF group (24.8% vs. 8.6%, P < 0.05) and lower graft survival rates (1 year, 93.3% vs. 100%; 5 years, 85.4% vs. 98.6%, respectively; P < 0.05). The presence of acute rejection in the SGF patients indicated a significantly decreased 5-year survival rate compared with the IGF group. The SGF group of patients with borderline pathology had a higher incidence of acute rejection than the IGF group, and significant increases in the expression of mRNA for pro-apoptotic genes (Fas-ligand, granzyme B and perforin) compared with the IGF group. In conclusion, SGF represents the activated immune state and is associated with poor graft outcome. Anti-rejection treatment or modified immunosuppressive regimen may thus be indicated for patients with SGF.

Evidence for the early involvement of interleukin 17 in human and experimental renal allograft rejection

Inflammatory processes can stimulate renal epithelial cells to release cytokines, chemoattractants and matrix proteins into the interstitium, thus contributing to interstitial injury during acute allograft rejection. To test the role of interleukin 17 (IL-17) in this process, cultured human renal epithelial cells (hRECs) were first established and treated with or without human IL-17 (hIL-17) for 2, 4, 8 and 10 h in vitro. Significant elevations of IL-6 and IL-8 levels were noted in the supernatants in a dose-dependent and time-dependent manner, as also for IL-6 mRNA expression. Secondly, using a rat acute allograft rejection model, the correlation between IL-17 expression and histopathological changes was serially studied. The results demonstrated that increased expression of IL-17 protein on infiltrating mononuclear cells (MNCs) was detectable on day 2. This corresponds to the borderline change of acute rejection according to the Banff classification, and it increased progressively to day 5. Serial study of IL-6, IL-8 and IL-17 mRNA expression of the renal allograft confirmed IL-17 mRNA expression in the allograft early on post-transplant day 2, whereas IL-6 and IL-8 expression started on day 3. Thirdly, IL-17 expression was observed in human renal allograft and urinary sediment. IL-17 protein expression was found in human subclinical (borderline) rejection renal allograft biopsy tissue and none in biopsy tissue not showing any evidence of rejection. There was also a 100% detectable rate of IL-17 mRNA expression in the MNCs of urinary sediment of patients with subclinical borderline rejection. These results demonstrate that hRECs exposed to IL-17 can produce inflammatory mediators with the potential to stimulate early alloimmune responses, which may also serve to give warning of acute renal allograft rejection.

Higher frequency of high-grade rejections in cardiac allograft patients after Quilty B lesions or grade 2/4 rejections

BACKGROUND

To better understand how different histologic patterns of allograft inflammation found on biopsies of human cardiac allografts progress to high-grade rejection, we undertook a statistical analysis of our institutional database to detect statistical patterns among different types of myocardial allograft inflammations found on sequential biopsies.

METHODS

Biopsies were analyzed for statistical associations between high-grade rejections (International Society of Heart and Lung Transplantation [ISHLT] grade > or = 3A/4) and the type of cardiac allograft inflammation found on prior biopsies. Case cross-over and case control designs were used to compare the antecedent patterns of inflammation on biopsies with high-grade rejection compared to biopsies with low-grade rejection, all within the same subject. Quilty lesions were correlated with cyclosporine levels.

RESULTS

Patients with Quilty B lesions or ISHLT grade 2/4 rejections show an increased risk for high-grade rejection on their next biopsies (Odds ratio 5.9 to 11.2). The presence of two pathological findings, especially Quilty B and grade 2/4 rejection, creates additional risk in excess of that found independently (Odds ratio >14). Quilty lesions are found only in cardiac allografts, and do not correlate with trough cyclosporine levels.

CONCLUSIONS

The morphological patterns of several types of human cardiac allograft inflammation found on sequential protocol biopsies are not randomly associated. Patients with grade 2/4 rejections and Quilty B lesions show an increased risk for high-grade rejections on their next biopsies. Quilty B lesions, similar to ISHLT grade 2/4 rejections, may represent subclinical rejection. Both are more likely to progress to a high-grade rejection.

IL-17 expression as a possible predictive parameter for subclinical renal allograft rejection

In the present study we have tried to establish the role of IL-17 in subclinical renal allograft rejection. In this animal model, renal grafts from BN (RT1n) were transplanted heterotopically into LEW (RT1l) rats. As controls, LEW grafts were transplanted into LEW rats. The histopathological examination demonstrated that the changes in the allograft kidney on day 2 were similar to those ranked as borderline changes according to the Banff classification scale. On day 2, the serum level of blood urea nitrogen (BUN) and creatinine were the same as on day 1. The examination of allograft cytokines mRNA showed that IL-17 mRNA expressed earlier on the second postoperative day, peaked at day 5, and then declined, becoming almost undetectable at day 9, when most rats died. IL-17 antigen was also proven, by histochemical staining, to be expressed early, however we could not find the same early appearance on other Th1/Th2 cytokines. In human renal biopsy samples, the IL-17 antigen could be found scattered around in the borderline changed rejected renal allografts without evidence of a serum creatinine increase, but was undetectable both in normal controls and in renal transplant tissue without signs of rejection. IL-17 mRNA was detected in the mononuclear cells of the urinary sediment of patients suffering from borderline subclinical rejection. From the above results we can hypothesize that IL-17 could serve as a predictive parameter for borderline subclinical renal allograft rejection in the future.

C4d deposition in acute rejection: an independent long-term prognostic factor

Peritubular capillary deposition of C4d has been demonstrated to be associated with both acute humoral and vascular rejection and increased graft loss. Whether it is an independent predictor of long-term graft survival rates is uncertain. The biopsies (n = 126) from all patients (n = 93) with a tissue diagnosis of acute rejection that were performed between July 1, 1995, and December 31, 1997, were classified according to Cooperative Clinical Trials in Transplantation (CCTT) criteria. Fresh frozen tissue was immunostained for C4d. There were 58 patients with CCTT type I (interstitial) rejection and 35 with CCTT type II (vascular) rejection. For 34 patients, at least one biopsy exhibited peritubular C4d deposition (C4d+ group). The C4d+ group had proportionately more female patients (P = 0.003), more patients with high (>30%) panel-reactive antibody levels (P = 0.024), more patients with resistance to conventional antirejection therapy (P = 0.010), and fewer patients with postrejection hypertension (P = 0.021) and exhibited a greater rate of graft loss (38 versus 7%, P = 0.001). Peritubular C4d deposition was associated with significantly lower graft survival rates in the CCTT type I rejection group (P = 0.003) and the CCTT type II rejection group (P = 0.003). Multivariate analyses demonstrated that peritubular C4d deposition (P = 0.0002), donor age (P = 0.0002), cold ischemic time (P = 0.0211), and HLA matches (P = 0.0460) were significant independent determinants of graft survival rates. Peritubular C4d deposition is a significant predictor of graft survival rates and is independent of histologic rejection type and a variety of clinical prognostic factors.