Effect of increasing baseline immunosuppression on the prevalence of clinical and subclinical rejection: a pilot study

Through the Looking Glass: Unraveling the Stage-Shift of Acute Rejection in Renal Allografts

Sub-optimal sensitivity and specificity in current allograft monitoring methodologies underscore the need for more accurate and reflexive immunosurveillance to uncover the flux in alloimmunity between allograft health and the onset and progression of rejection. QSant—a urine based multi-analyte diagnostic test—was developed to profile renal transplant health and prognosticate injury, risk of evolution, and resolution of acute rejection. Q-Score—the composite score, across measurements of DNA, protein and metabolic biomarkers in the QSant assay—enables this risk prognostication. The domain of immune quiescence—below a Q-Score threshold of 32—is well established, based on published AUC of 98% for QSant. However, the trajectory of rejection is variable, given that causality is multi-factorial. Injury and subtypes of rejection are captured by the progression of Q-Score. This publication explores the clinical utility of QSant across the alloimmunity gradient of 32–100 for the early diagnosis of allograft injury and rejection.

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection

Prognostic biomarkers of T cell-mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA-DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor-specific antibodies (P = .002). HLA-DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA-DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA-DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA-DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA-DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

Subclinical Inflammation in Renal Transplantation

The standardization of renal allograft pathology began in 1991 at the first Banff Conference held in Banff, Alberta, Canada. The first task of transplant pathologists, clinicians, and surgeons was to establish diagnostic criteria for T-cell-mediated rejection (TCMR). The histological threshold for this diagnosis was arbitrarily set at "i2t2": a mononuclear interstitial cell infiltrate present in at least 25% of normal parenchyma and >4 mononuclear cells within the tubular basement membrane of nonatrophic tubules. TCMR was usually found in dysfunctional grafts with an elevation in the serum creatinine; however, our group and others found this extent of inflammation in "routine" or "protocol" biopsies of normally functioning grafts: "subclinical" TCMR. The prevalence of TCMR is higher in the early months posttransplant and has decreased with the increased potency of current immunosuppressive agents. However, the pathogenicity of lesser degrees of inflammation under modern immunosuppression and the relation between ongoing inflammation and development of donor-specific antibody has renewed our interest in subclinical alloreactivity. Finally, the advances in our understanding of pretransplant risk assessment, and our increasing ability to monitor patients less invasively posttransplant, promises to usher in the era of precision medicine.

Graft Function and Intermediate-Term Outcomes of Kidney Transplants Improved in the Last Decade: Analysis of the United States Kidney Transplant Database

Supplemental digital content is available in the text.

Background

Previous analyses of the United States transplant database regarding long-term outcomes in kidney transplantation have shown minimal improvement in the rate of long-term graft loss. This study sought to analyze intermediate-term outcomes and graft function at 6 months in kidney transplantation in adult living and deceased donor recipients in the last decade.

Methods

Survival analysis was performed based on the year of transplant between 6 months and 3 years’ posttransplant. The Chronic Kidney Disease Epidemiology Collaboration estimated glomerular filtration rate (eGFR) was determined at 6 months.

Results

The unadjusted graft survival between 6 months and 3 years improved significantly in the latter half of the decade in both deceased and living donor kidney recipients. Cox analysis showed a 33% reduction in the rate of graft loss and that the improvement in graft survival was due to similar improvements in both death-censored graft and death with graft function survival. A 10% improvement in median eGFR occurred despite worsening donor demographics over time in both donor types. This improvement in eGFR and graft survival occurred in association with a consolidation of chronic discharge immunosuppression from a variety of combinations to over 85% of recipients receiving tacrolimus and mycophenolate derivative immunosuppression.

Conclusions

In the latter half of last decade graft survival improved in adult kidney transplant recipients. The improvement in graft survival occurred in temporal association with an improvement in median eGFR at 6 months and consolidation of discharge immunosuppression in most patients to tacrolimus and mycophenolate derivatives.

Early Steroid Withdrawal in Recipients of a Kidney Transplant From a Living Donor: Experience of a Single Mexican Center

BACKGROUND

Early steroid withdrawal (ESW) can improve lipid and hemodynamic profiles without severe acute rejection (AR) events in renal transplant patients. Our objective was to evaluate the effects of ESW on the frequency and severity of AR.

METHODS

A randomized, open-label, controlled clinical trial was performed on renal transplant recipients with a follow-up of 12 months. In the ESW group, patients were selected for corticosteroid treatment withdrawal on the fifth day post transplantation. In the Control group, patients continued with steroid treatment. All patients were over 18 years of age with panel reactive antibody (PRA) class I and II HLA <20%.

RESULTS

In total, 71 patients, 37 in the ESW group (52.1%) and 34 in the Control group (47.9%), had comparable AR incidences at the end of the follow-up (16% vs 15%) (NS) (RR = 1.20, 95% CI = 0.32-3.33). Although renal graft survival was similar between the ESW and Control groups (87% vs 94%), renal function was superior in the ESW group (85 vs 75 mL/min). Additionally, hypertension was less frequent in the ESW group (3% vs 35%), requiring the use of fewer antihypertensives (8% vs 50%).

CONCLUSIONS

ESW was also associated with better blood pressure control and similar AR risk. The ESW group exhibited stable renal function.

Protocol Biopsies: Utility and Limitations

As both T cell and antibody-mediated rejection can have a subclinical phase, protocol biopsies provide an early opportunity to intervene before the onset of clinical allograft dysfunction. Protocol biopsies are usually done after reperfusion to establish baseline, between 3 and 6 months to identify subclinical rejection, and at 6-12 months to assess chronicity and persistent inflammation that have prognostic implication. Treatment of both subclinical T cell and antibody-mediated rejection prevents progression of rejection and development of interstitial fibrosis/tubular atrophy or transplant glomerulopathy. Although subclinical rejection has become less frequent in low-risk patients on triple immunosuppression containing tacrolimus, protocol biopsies may still be useful in selected population. Protocol biopsies are more likely to benefit patients at higher risk for rejection, including those who are highly sensitized, transplanted across donor-specific antibody barriers, or on calcineurin inhibitor/corticosteroids sparing regimens. Interstitial fibrosis on protocol biopsies, especially in conjunction with persistent inflammation, predicts lower allograft survival.

The impact of calcineurin inhibitors on graft survival

The discovery of the first calcineurin inhibitor (CNI), cyclosporine, represents a watershed event in the history of immunosuppression, as it was the first drug shown to reversibly inhibit T-lymphocyte function, therefore allowing for one of the major breakthroughs in modern medicine, that of organ transplantation. Calcineurin inhibitors remain the most effective and widely used immunosuppressive agents in organ transplantation today. The 2010 OPTN/SRTR Annual Report showed that 96% of renal transplant recipients were on CNI at the time of discharge from hospital. The prolonged use of CNI, however, may result in renal toxicity, renal dysfunction and eventual renal failure in both recipients of renal and other solid organ transplants, as well as in patients treated with these agents for autoimmune diseases. This brief review, while acknowledging that CNI toxicity does indeed exist, will focus on the successful use of CNI in renal transplant recipients, highlighting recent observations that provide alternative explanations for some of the adverse outcomes that have been attributed to CNI nephrotoxicity in the past.

Urinary proteomic shotgun approach for identification of potential acute rejection biomarkers in renal transplant recipients

BACKGROUND

Acute rejection (AR) episodes in renal transplant recipients are suspected when plasma creatinine is elevated and other potential causes out ruled. Graft biopsies are however needed for definite diagnosis. Non-invasive AR-biomarkers is an unmet clinical need. The urinary proteome is an interesting source in the search for such a biomarker in this population.

METHODS

In this proof of principle study, serial urine samples in the early post transplant phase from 6 patients with biopsy verified acute rejections and 6 age-matched controls without clinical signs of rejection were analyzed by shotgun proteomics.

RESULTS

Eleven proteins fulfilled predefined criteria for regulation in association with AR. They presented detectable regulation already several days before clinical suspicion of AR (increased plasma creatinine). The regulated proteins could be grouped by their biological function; proteins related to growth and proteins related to immune response. Growth-related proteins (IGFBP7, Vasorin, EGF and Galectin-3-binding protein) were significantly up-regulated in association with AR (P = 0.03) while proteins related to immune response (MASP2, C3, CD59, Ceruloplasmin, PiGR and CD74) tended to be up-regulated ( P = 0.13).

CONCLUSION

The use of shotgun proteomics provides a robust and sensitive method for identification of potentially predictive urinary biomarkers of AR. Further validation of the current findings is needed to establish their potential clinical role with regards to clinical AR diagnosis.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT00139009.

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.

Early subclinical rejection as a risk factor for late chronic humoral rejection

BACKGROUND

Subclinical rejection and interstitial fibrosis and tubular atrophy (IF/TA) in protocol biopsies are associated with outcome. We study the relationship between histologic lesions in early protocol biopsies and histologic diagnoses in late biopsies for cause.

MATERIALS AND METHODS

Renal transplants with a protocol biopsy performed within the first 6 months posttransplant between 1988 and 2006 were reviewed. Biopsies were evaluated according to Banff criteria, and C4d staining was available in biopsies for cause.

RESULTS

Of the 517 renal transplants with a protocol biopsy, 109 had a subsequent biopsy for cause which showed the following histological diagnoses: chronic humoral rejection (CHR) (n=44), IF/TA (n=42), recurrence of the primary disease (n=11), de novo glomerulonephritis (n=7), T-cell-mediated rejection (n=4), and polyoma virus nephropathy (n=1). The proportion of retransplants (15.9% vs. 2.3%, P=0.058) and the prevalence of subclinical rejection were higher in patients with CHR than in patients with IF/TA (52.3% vs. 28.6%, P=0.0253). Demographic donor and recipient characteristics and clinical data at the time of protocol biopsy were not different between groups. Logistic regression analysis showed that subclinical rejection (relative risk, 2.52; 95% confidence interval, 1.1-6.3; P=0.047) but not retransplantation (relative risk, 6.7; 95% confidence interval, 0.8-58.8; P=0.085) was associated with CHR.

CONCLUSION

Subclinical rejection in early protocol biopsies is associated with late appearance of CHR.

The possible role of early post-transplant inflammation in later anemia in kidney transplant recipients

Delayed kidney graft function and acute rejection in the early post-transplant period affect both short and long-term allograft survival. Allograft rejection, as an inflammatory state, results in increased erythropoietin resistance, which leads to decreased haemoglobin (Hb) level. We conducted this study to evaluate whether inflammation in the early post-transplant period could predict later anemia.This is a retrospective cohort study based on the analysis of 64 existing clinical records.

PREDICTOR

White blood cells (WBC) count obtained by the end of the first week post-transplant (W1). Covariates: Donor's age, recipient's age and sex.

OUTCOME

Anemia identified at 12 months (M12) post engraftment. Median WBC count at W1 was 9,5 x103/microL (5th - 95th percentile 5,2 x103/microL -17,8 x103/microL). Mean Hb values at M12 were 129,9 +/- 20,3 g/L, in males 136,2 +/- 20,1 g/L and in females 119,4 +/- 16,2 g/L. The significant correlation was found between WBC at W1 and Hb at M12. Pearson coefficient of correlation r was -0,26, and 95% confidence interval (CI) for r was -0,47 to -0,015 (p=0,03). Univariate logistic regression showed significant association between WBC at W1 and Hb at M12 (OR 1,20; 95% CI 1,04 to 1,39, p=0,01). After the adjustment for donor's and recipient's age by transplantation and recipient's sex, multiple regression showed that WBC count remained predictive of anemia at M12 (OR 1,17; 95% CI 1,01 to 1,36, p=0,03). Early post-transplant inflammatory response predicts later anemia in kidney transplant recipients. An increase in WBC count in the first week post-transplant by 109/L increases the risk for anemia after twelve months by 17%.

Prevalence of clinical rejection after surveillance biopsies in pediatric renal transplants: does early subclinical rejection predispose to subsequent rejection episodes?

We analyzed rates of both SCR and CR in children receiving SB at three months post-transplant to determine if SCR predisposed patients to acute CR. Acute rejection was defined according to Banff criteria to include borderline classification or higher. All cases of SCR and CR were treated with anti-rejection protocols. Between October 2004 and July 2008, 89 SB were performed at three months post-transplant. Twenty-six cases of SCR were detected (29%). Sixteen patients experienced 22 episodes of biopsy-proven CR occurring after SB, including seven episodes following SCR and 15 after normal SB. The onset of CR varied from one to 27 months after SB and occurred at similar intervals for cases with SCR and normal SB. The percentage of patients remaining free of CR at 30 months post-transplant was similar in patients with SCR and normal SB. Renal function and graft survival at 30 months also were no different between patients with SCR and those with normal SB. Early-SCR, when treated with rejection protocols, is not a prognostic indicator for subsequent CR episodes.

Post-transplant monitoring of renal allografts: are we there yet?

Transplantation has emerged as the therapy of choice for many patients with end organ failure. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient to balance the risk for rejection and over-immunosuppression. This will require diagnostic tools that can detect harmful processes in the allograft early, and that can be measured repeatedly. This review will consider recent advances in our understanding of the molecular nature of these processes and how this information is being utilized to design novel diagnostic assays to non-invasively monitor allografts. Highlighted is the need for large-scale prospective multi-centre studies to validate assays that show early promise in single centre studies.

The impact of immune gene polymorphisms in kidney and liver transplantation

Since the completion of the Human Genome Project, it has become clear that genetic variation exists among individuals that can affect functional gene expression. This finding raises the possibility that differences in genetic phenotypes may account for the interindividual responses seen in the context of the alloimmune response. This review highlights studies examining the relative role of immunologic gene polymorphism in the context of renal and liver transplant outcomes (eg, acute rejection and graft survival). Furthermore, it examines the limitations and pitfalls in the study designs and concludes with the potential of single nucleotide polymorphism analysis in the future care of transplant recipients.

Genetic prediction of renal transplant outcome

PURPOSE OF REVIEW

In the present study, we reviewed recent publications regarding potential genetic predictors of transplant outcome, including acute rejection, metabolism of immunosuppressive medications, long-term transplant outcome, and posttransplant complications.

RECENT FINDINGS

Recent studies are based on the candidate gene analysis; specifically, cytokine genes and innate immune response molecules present popular targets for studies of acute rejection and long-term outcome. Pharmacogenomic studies are mostly focused on the genes of drug targets or the corresponding enzymes metabolizing the drug. Posttransplant complications (i.e. infections, diabetes, and malignancies) are associated with a variety of genes of different pathways. Most of the studies are based on just recipient, but not donor, genotype analysis. Positive results are balanced by reports of no association when evaluating the same genetic polymorphisms. Some of the reports might be affected by insufficient study design, including small sample size, lack of adjustment for potential confounders, and multiple comparisons.

SUMMARY

The field remains controversial because of differences in populations, study design, and statistical methods. Studies are based on candidate gene analysis; however, genome-wide association studies are lacking. Future research should be directed at better designed studies, larger sample size, evaluating both recipients and donors, and implementation of genome-wide association studies.

Impact of Banff borderline acute rejection among renal allograft recipients

OBJECTIVE

This study was performed to determine the incidence, treatment, and outcomes of Banff borderline acute rejection (AR) among renal transplant recipients.

PATIENTS AND METHODS

We reviewed the courses of adult kidney transplant recipients with borderline AR on clinically indicated biopsies performed at our center from January 2003 to July 2006. Patients with complete transplant records and serum creatinine values at 6 and 12 months were included in this study. The primary outcome measures were serum creatinine values at 1 to 2 weeks after treatment, and at 6 and 12 months after graft biopsy.

RESULTS

Among 428 renal graft biopsies, borderline AR was observed in 100 cases (23%). Patients were maintained on the same immunosuppression. The 86 who had complete data were included in the study. Seventy-eight percent of the patients received treatment with 3 days of methylprednisolone, while 22% were untreated. Mean serum creatinine values in the treated group were 2.9 +/- 1.0, 2.6 +/- 2.5, and 3.0 +/- 2.9 mg/dL at the time of biopsy, and at 6 and 12 months thereafter, respectively. In the untreated group, mean serum creatinine values were 2.2 +/- 1.0, 1.9 +/- 0.8, and 2.3 +/- 1.2 mg/dL during biopsy, and at 6 and 12 months thereafter, respectively. There was no significant difference in the serum creatinine at any of the measured time points between the 2 groups. Twelve patients had repeat renal graft biopsies which showed AR (6%), chronic allograft nephropathy (2.4%), and borderline changes (3.8%). Nine of the patients in the treated group eventually developed graft loss.

CONCLUSIONS

Patients with borderline AR showed a progressive increase in serum creatinine over time. They should be followed closely; immunosuppression may need to be intensified.

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: what have we learned from protocol biopsies?

Chronic allograft nephropathy, characterized by interstitial fibrosis and tubular atrophy, is still a major cause of graft loss after kidney transplantation. The complex pathophysiology of chronic allograft nephropathy is still poorly understood, and could be clarified by a more systematic performance of implantation and protocol biopsies of the renal allograft. This review highlights the contribution of implantation and protocol biopsies to our current knowledge of the complex interaction of multiple processes, ultimately leading to the development of interstitial fibrosis and tubular atrophy in the transplanted kidney. In addition, the safety and the limitations of protocol biopsies are discussed, as well as potential future directions for clinical practice and clinical research.

Lack of benefit of early protocol biopsies in renal transplant patients receiving TAC and MMF: a randomized study

We conducted a randomized, multicenter study to determine whether treatment of subclinical rejection with increased corticosteroids resulted in beneficial outcomes in renal transplant patients receiving tacrolimus (TAC), mycophenolate mofetil (MMF) and prednisone. One hundred and twenty-one patients were randomized to biopsies at 0,1,2,3 and 6 months (Biopsy arm), and 119 to biopsies at 0 and 6 months only (Control arm). The primary endpoint of the study was the prevalence of the sum of the interstitial and tubular scores (ci + ct)> 2 (Banff) at 6 months. Secondary endpoints included clinical and subclinical rejection and renal function. At 6 months, 34.8% of the Biopsy and 20.5% of the Control arm patients had a ci + ct score >or= 2 (p = 0.07). Between months 0 and 6, clinical rejection episodes were 12 in 10 Biopsy arm patients and 8 in 8 Control arm patients (p = 0.44). Overall prevalence of subclinical rejection in the Biopsy arm was 4.6%. Creatinine clearance at 6 months was 72.9 +/- 21.7 in the Biopsy and 68.90 mL/min +/- 18.35 mL/min in the Control arm patients (p = 0.18). In conclusion, we found no benefit to the procurement of early protocol biopsies in renal transplant patients receiving TAC, MMF and prednisone, at least in the short term. This is likely due to their low prevalence of subclinical rejection.

Diagnostic Tools for Monitoring Kidney Transplant Recipients

Recent advancements in immunobiology have introduced several new diagnostic tools for monitoring kidney transplant recipients. These have been added to more established tests that, although imperfect, remain important benchmarks of diagnostic utility. Both new and old tests can be characterized with regard to their practicality, and as to whether they detect aberrant function or define the cause of dysfunction. Unfortunately, no current test is both practical and specific to a particular disease entity. Accordingly, the diagnosis of graft dysfunction remains dependent on the proper use and interpretation of many studies. This article reviews the current assays that have been evaluated in the clinic for the diagnosis of renal allograft-related diseases. These are limited to assays based on routinely obtainable samples such as blood, biopsy tissue, and urine. Newer studies are presented, along with more mundane assays, to highlight the practical use of studies regardless of their degree of mechanistic sophistication.

Developing a tool for noninvasive monitoring of renal allografts

Renal transplantation has emerged as the therapy of choice for many patients with end-stage renal disease. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient at every time point post transplant, balancing the risk for rejection and over-immunosuppression. Such individualized treatment will require assays that can detect harmful processes in the allograft early and that can be measured repeatedly. In this review, advantages and disadvantages of current assays to monitor renal allografts noninvasively and how proteomic technology might contribute to the development of novel biomarkers to improve patient management will be discussed.

The aetiology and pathogenesis of chronic allograft nephropathy

Renal transplantation is the ultimate form of renal replacement therapy, and is the treatment of choice for many patients with end-stage renal failure. The advent of calcineurin inhibitor based immunosuppression resulted in the 1-year renal allograft failure rate dropping from around 50% twenty years ago to less than 10% in more recent times. Despite a massive improvement in renal allograft survival in the first year following transplantation 10-year graft survival can be as low as 50%. Chronic allograft nephropathy (CAN) is recognised as the main cause of renal allograft failure following the first year after transplantation. The diagnosis of CAN can only be made histologically. Typically biopsy specimens in grafts with CAN demonstrate an overall fibrotic appearance effecting the vascular endothelium, renal tubules, interstitium, and glomerulus. The risk factors for CAN are divided into alloimmune and alloimmune independent. Alloimmune dependent factors include acute cellular rejection, severity of rejection, subclinical rejection and HLA mismatch. Alloimmune independent factors such as delayed graft function, donor age, Cytomegalovirus infection, donor/recipient co-morbidity and of course calcineurin inhibitor toxicity are important in the development of CAN. The pathogenesis of CAN is complex, multifactorial, and unfortunately incompletely understood. There are a number of pivotal steps in the initiation and propagation of the fibrosis seen in biopsy specimens from kidneys with CAN. Endothelial activation in response to one or more of the aforementioned risk factors stimulates leukocyte activation and recruitment. Recruited leukocytes subsequently infiltrate through the endothelium and induce key effector cells to secrete excessive and abnormal extracellular matrix (ECM). Enhanced deposition of ECM is a histological hallmark of CAN. This paper aims to present a concise yet accurate and up-to-date review of the literature concerning the aetiological factors and pathological processes which are present in the generation of CAN.

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.

Treatment of subclinical rejection diagnosed by protocol biopsy of kidney transplants

BACKGROUND

Subclinical rejection (SCR) causes chronic allograft damage, which may be prevented by antirejection therapy.

METHODS

A pilot study of the effect of routine treatment of SCR was performed in 88 recipients of either a kidney (n=59) or combined kidney-pancreas transplant (n=29) undergoing protocol biopsy (PBX) surveillance at 1 and 3 months, using calcineurin inhibitors, mycophenolate mofetil, and corticosteroid therapy.

RESULTS

SCR was seen in 46.6% (41/88 patients), as 30 borderline and 11 acute SCR. From 279 transplant biopsies, the prevalence of SCR was 25% (22/88) at 1 month, 10.2% (9/88) at 3 months, and 8.3% (2/24) at 12 months PBX. Treatment included bolus intravenous or oral corticosteroids (n=20) and augmented immunosuppression, either by conversion to tacrolimus (n=6) or increased doses of maintenance therapy (n=14), whereas OKT3 was used in one case of subclinical vascular rejection. Borderline episodes were not treated in 12 patients. In biopsies taken to assess therapeutic response, persistent SCR was present in 46.1% (6/13). Treatment of SCR at 1 month was followed by lower acute Banff sum scores at 3 months PBX (P<0.01-0.0001). Early chronic damage was already present in the 1 month PBX, associated with SCR (P<0.0005 versus without SCR), although by 3 months these differences were lost. Rates of opportunistic infections and BK nephropathy were not increased by SCR treatment.

CONCLUSION

Early chronic allograft damage was associated with SCR and therapy appeared to ameliorate further immune-mediated injury, although the efficacy of corticosteroids alone may be inadequate. A controlled trial of therapy for SCR is warranted.

Untreated rejection in 6-month protocol biopsies is not associated with fibrosis in serial biopsies or with loss of graft function

Donor age, calcineurin inhibitor nephrotoxicity, and acute rejection are the most significant predictors of chronic allograft nephropathy. Protocol biopsies, both in deceased- and living-donor renal grafts, have shown that cortical tubulointerstitial fibrosis correlates with graft survival and function. The impact of not treating subclinical acute rejection (SAR) is less clear. In this study, 126 de novo renal transplant recipients were randomly assigned to receive area-under-the-curve-controlled exposure of either a cyclosporine or a tacrolimus-based immunosuppressive regimen that included steroids, mycophenolate mofetil, and basiliximab induction. Protocol biopsies were taken before and 6 and 12 mo after transplantation. The prevalence of SAR was determined retrospectively. Fibrosis was evaluated by quantitative digital analysis of Sirius red staining in serial biopsies. Donor age correlated significantly with tubulointerstitial fibrosis in pretransplantation biopsies and inferior graft function at month 6 (rtau = -0.26; P = 0.033). Acute rejection incidence was 11.5%, and no clinical late rejection occurred. The prevalence of SAR at 6 mo was 30.8% but was not associated with differences in serial quantitative Sirius red staining at 6 or 12 mo, proteinuria, or progressive loss of GFR up to 2 yr. No differences were found in donor variables, histocompatibility, rejection history, or exposure of immunosuppressants. Controlled individualized calcineurin inhibitor exposure and subsequent tapering resulted in a low early acute rejection rate and prevented late acute rejection. Because, by design, we did not treat SAR, these results provide evidence that asymptomatic infiltrates in 6-mo surveillance biopsies may not be deleterious in the intermediate term. There is need for reliable biomarkers to prove that not all cell infiltrates are equivalent or that infiltrates may change with time.

Better renal function with enhanced immunosuppression and protocol biopsies after kidney transplantation in children

Subclinical rejection may be associated with decreased graft function after renal transplantation (Tx). Detection by protocol biopsies and treatment could thus be important for the long-term prognosis. We have earlier discovered that glomerular filtration rate (GFR) declined in young children during the first 18 months. Consequently, we slightly enhanced and individualized each patient's immunosuppression. This was a retrospective study of 59 pediatric renal Tx patients between 1995 and 2001. The 35 historical controls received triple-therapy of azathioprine, methylprednisolone and cyclosporine. GFR was measured by protocol at discharge, 6 and 18 months, and a core biopsy was obtained at 18 months. The 24 study patients in addition received basiliximab, had GFR measured at 3 and 12 months, and a biopsy taken at 3 months. Based on histology and function, immunosuppression was individually adjusted. The groups were compared for GFR and histology at 18 months after Tx. There were less acute rejection episodes in the study group (0.38 vs. 1.23 per patient) and serum creatinine concentrations were lower. Subclinical rejection was detected and treated in 39% at 3 months. There were more chronic changes in the control (47%) than in the study group (29%) at 18 months. GFR was significantly higher in the study group at 18 months (87 vs. 68 mL/min/1.73 m(2)), most remarkably in patients < or =2 yr of age (99 vs. 68 mL/min/1.73 m(2)). Detection of subclinical rejection and slightly enhanced and individualized immunosuppression improved GFR 18 months after renal Tx, especially in the youngest patients.

Protocol Transplant Biopsies: Are They Really Needed?

Studies suggest that surveillance or protocol biopsies that are performed during the first year after kidney transplantation may be clinically useful in identifying early acute rejection or chronic allograft nephropathy at a point when they may be amenable to treatment. Although the benefit of this approach has yet to be evaluated in large, multicenter, prospective trials, numerous studies suggest that implementation of protocol biopsies may improve long-term graft function. In particular, a number of reports suggest that detection of chronic allograft nephropathy in early protocol biopsies is predictive of subsequent graft function and loss and that early treatment may have a dramatic effect on the outcome of the graft. Protocol biopsies also have the potential to be of great value in high-risk patients, such as those with delayed graft function, by allowing for early intervention for acute rejection. Furthermore, the procedure seems to be relatively straightforward and safe. Nevertheless, paucity of data has meant that clear proof of a benefit of early treatment of subclinical rejection and chronic allograft nephropathy detected by protocol biopsy is lacking. Moreover, the optimal timing of protocol biopsies and reliable methods to quantify the histologic changes observed in biopsy specimens have yet to be determined. This review discusses the pros and cons of protocol biopsies and considers the place of this procedure in the routine treatment of kidney transplant patients.

Significance of subclinical rejection in early renal allograft biopsies for chronic allograft dysfunction

To determine the significance of early subclinical rejection of renal allografts, we reviewed 127 biopsy specimens obtained soon after transplantation. Histological finding was categorized according to a modification of the Banff scheme as: acute rejection (AR), borderline changes (BL); non-specific inflammatory changes, (NI) and no rejection (NR). Subclinical rejection was defined as AR, BL or NI. Patients with BL or NI were divided into two groups; one was treated with high-dose methylprednisolone (MP), the other remained untreated. Freedom from chronic allograft dysfunction (defined as non-doubling of serum creatinine 5 yr after transplantation) was significantly more frequent in the NR group (89%) than in the BL (70%) and AR (64%) groups. At 1 yr after transplantation, mean serum creatinine had increased significantly only in the untreated group (p < 0.05), and re-biopsy showed that interstitial fibrosis had developed to a significantly greater extent in the untreated group than in the treated group (p < 0.01). Subclinical rejection in the early protocol biopsies correlated closely with subsequent allograft dysfunction. High-dose MP treatment for early subclinical rejection may be effective in suppressing the development of interstitial fibrosis at 1 yr after transplantation.

Sirolimus: a new option in transplantation

This review of immunosuppression in renal transplantation has allowed us to highlight the deleterious effect of calcineurin inhibitor nephrotoxicity and to emphasise the importance of sirolimus. Now, a whole new set of possibilities has opened up in immunosuppression: sirolimus-based immunosuppression without calcineurin inhibitors; sirolimus in combination with calcineurin inhibitors in reduced doses; early calcineurin inhibitor withdrawal from a regimen that combines sirolimus, calcineurin inhibitors and steroids; and calcineurin inhibitor conversion to sirolimus when the first signs of graft nephrotoxicity appear. These new strategies in immunosuppression in renal transplantation are associated with good results in graft and patient survival in year 1, and with better renal function. Therefore, we can hope for better long-term results in transplantation, with a significant increase in the graft half-life and in the patient survival.

Randomized prospective trial of early steroid withdrawal compared with low-dose steroids in renal transplant recipients using serial protocol biopsies to assess efficacy and safety

BACKGROUND

Corticosteroid therapy after renal transplantation is associated with many adverse effects. Newer immunosuppressive agents may allow for safe and effective reductions in dose or early steroid withdrawal.

METHODS

In this prospective, single-center clinical trial, 60 patients were randomized into 2 groups: control patients (n = 28), who received low doses of prednisone throughout, and study patients (n = 32), who were withdrawn from steroids 7 days posttransplant. Patients received a limited course of rabbit antilymphocyte globulin (rALG) induction therapy, tacrolimus (TAC), and mycophenolate mofetil (MMF). Patients were followed for clinical outcomes and renal function. Protocol biopsies were performed at 1, 6, and 12 months.

RESULTS

Clinical rejections occurred in 11% of controls and 13% of study patients. Renal function was well maintained and equivalent in both groups. In all, 111 protocol biopsies were performed without complications. Subclinical rejection was noted in only 2 protocol biopsies, and borderline changes were seen in 12 biopsies, all of which were distributed equally between both groups. Unsuspected acute TAC toxicity was seen in 8 biopsies. Protocol biopsies led to changes in therapy in 10% of patients. In both groups, serial protocol biopsies demonstrated increased allograft fibrosis over time, which was significant at 1 year in the steroid withdrawal group.

CONCLUSION

The immunosuppressive combination of rALG, TAC, and MMF prevents subclinical rejection and the need for high doses of steroids after transplantation. However, continual low-dose steroid therapy may aid in preventing chronic allograft fibrosis. Protocol biopsies help define the short-term and long-term risks of steroid withdrawal therapy.

The Relative Importance of Cytokine Gene Polymorphisms in the Development of Early and Late Acute Rejection and Six-Month Renal Allograft Pathology

BACKGROUND

Acute rejection episodes and 6-month protocol biopsy acute pathology are highly correlated with long-term outcomes in renal transplant recipients. Recurrent, vascular, and late rejections are particularly deleterious.

METHODS

We determined the relative contribution of human leukocyte antigen matching, cytokine genotypes, delayed graft function (DGF), and baseline immunosuppression to the development of acute rejection and allograft pathology in 118 renal transplant recipients.

RESULTS

Multivariate logistic regression modeling demonstrated that the adjusted odds ratio and 95% confidence interval for recurrent (> or =2) early rejections (0-3 months) increased linearly for high (H) > intermediate (I) > low (L) interferon-gamma (1.8; 1.1-3.2) and tumor necrosis factor (TNF)alpha (3.0; 1.3-6.9) genotype, whereas every 1 microg/L increase in the cyclosporine A level was protective (0.991; 0.984-0.999). The odds ratio for recurrent late rejections (4-6 months) increased for H > I > L TNFalpha (5.1; 1.8-14.7) genotype and DGF (7.1; 1.6-30.2), whereas H > I/L transforming growth factor-beta1 genotype decreased the relative risk (0.09: 0.02-0.49). Vascular rejection was only predicted by H > I > L TNFalpha phenotype (3.0; 1.2-7.9). The odds ratio for the 6-month Banff Acute Score (6A > or= 4) increased for H > I > L TNFalpha (2.7; 1.1-6.7) and interleukin-10 (3.4; 1.2-6.2) genotype, and DGF (3.4; 1.1-11.5). Treatment of early subclinical rejection decreased the relative risk (0.20; 0.07-0.62).

CONCLUSIONS

High transforming growth factor-beta1 producer phenotype seems to be protective against acute inflammation, whereas H and I interferon-gamma, TNFalpha, and interleukin-10 producer genotypes correlate with adverse outcomes. Cytokine genotyping identifies individuals who may benefit from more intensive surveillance and treatment posttransplant.

Protocol biopsies after kidney transplantation

Numerous studies have investigated features of allograft injury in renal biopsies obtained in stable kidney transplants. Evaluation of protocol biopsies has revealed a considerably high prevalence of subclinical acute rejection (SAR) and chronic allograft nephropathy (CAN) already in early phases after transplantation. The meanwhile well-established association of SAR and CAN in protocol biopsy with long-term allograft failure and the finding of superior allograft outcome after treatment of SAR in a randomized prospective study may point to clinical relevance of this procedure. In this review, potential benefits and risks associated with kidney allograft biopsy in stable renal transplant recipients are discussed.

Molecular diagnosis of renal-allograft rejection: correlation with histopathologic evaluation and antirejection-therapy resistance

BACKGROUND

Because histopathologic criteria cannot always predict the pathogenesis and response to curative antirejection therapy, new hope derives from the molecular analysis of intragraft immunologic markers. We studied whether the cutoff of intragraft expression level of T-cell activation markers may define subgroups of acute rejection differing either in type of rejection or clinical outcome.

METHODS

Forty-three human renal-allograft biopsies were quantified for mRNA expression of granzyme B, Fas ligand, interferon (IFN)gamma, interleukin (IL)-4, and IL-6 with a reverse-transcriptase real-time quantitative polymerase chain reaction (RT-PCR) method. Expression levels were correlated with the histopathologic rejection type according to the Banff 1997 classification criteria, and with the sensitivity to the antirejection immunosuppressive therapy, by means of receiver operating-characteristic (ROC) curves.

RESULTS

Granzyme B and Fas ligand mRNA expression up-regulation correlated with all allograft rejection types (P<0.01 for all). Moreover, granzyme B showed the highest sensitivity (90%) and specificity (78%) for the potential detection of histologic borderline changes that will require immunosuppressive therapy (area under the curve [AUC]=0.856, P<0.01). Curative antirejection-therapy resistance of overt, acute-rejection episode was significantly associated with higher Fas ligand gene expression (AUC=0.764, P<0.01, sensitivity [71%], specificity [99.5%]).

CONCLUSIONS

Real-time RT-PCR quantification of the over-expression of the granzyme B gene in kidney-graft biopsies has proved to be as reliable in detecting acute rejection as histologic assessment. Furthermore, we demonstrate that the simultaneous measurement of the mRNA up-regulation of Fas ligand might represent an efficient new tool for the prediction of pejorative outcome of acute rejection.

Insights into subclinical rejection

Several groups have performed graft biopsies at set times posttransplant ("protocol biopsies") and found unequivocal histologic criteria for acute rejection in a high proportion of patients with stable graft function. The significance of "subclinical" rejection remains controversial. Our group and others have shown that clinically silent infiltrates have inflammatory and cytotoxic potential. Furthermore, in a randomized trial, we demonstrated that treatment of subclinical rejection results in better graft histology and renal function. Although a decrease in the prevalence of subclinical rejection may reduce the rate of late graft losses, the risks and cost of protocol biopsies require that noninvasive methods for the diagnosis of subclinical rejection be developed.

Baseline Immunosuppression is Associated with Histological Findings in Early Protocol Biopsies

BACKGROUND

Protocol biopsies performed in stable renal allografts show different degrees of acute and chronic lesions that have been related with graft outcome. However, the utility of protocol biopsies to manage baseline immunosuppression has not been well characterized.

METHODS

We performed a case-control study to compare histological lesions observed in protocol biopsies in 49 patients treated with tacrolimus (TAC), mycophenolate mofetil (MMF), and prednisone to 49 patients treated with cyclosporine Neoral (CsA), MMF, and prednisone. Histological lesions were graded according to 1997 Banff criteria. The analysis was done according to an intention-to-treat basis.

RESULTS

Patients treated with TAC displayed in the protocol biopsy a lower acute score (0.61+/-1.01 vs. 1.26+/-1.45; P=0.0115) and a similar chronic score (1.57+/-1.97 vs. 1.51+/-1.59; P=NS). Transplant glomerulopathy was also lower in TAC treated patients (0.02+/-0.14 vs. 0.20+/-0.41; P=0.0037). Univariate and multivariate logistic regression analysis showed that the presence of acute inflammation was associated with tacrolimus treatment (relative risk [RR]: 0.30, 95% confidence interval [CI]: 0.11-0.84; P=0.0211) and the time of biopsy (RR per month: 0.56, 95% CI: 0.32-0.97; P=0.0394). The presence of chronic lesions was only associated with serum creatinine at the time of biopsy (RR: 1.01, 95% CI: 1.00-1.02; P=0.0439).

CONCLUSIONS

The incidence of inflammatory lesions and transplant glomerulopathy is lower in patients treated with TAC than in patients treated with CsA. These data suggest that baseline immunosuppression could influence the severity of histological lesions in stable grafts.

Improved Clinical Outcomes in Chinese Renal Allograft Recipients Receiving Lower Dose Immunosuppressants

BACKGROUND

The application of potent immunosuppressants has decreased the incidence of acute rejection and increased short- and long-term graft survival; however, these drugs cause a variety of complications. In China, many transplant centers have adopted the immunosuppressive protocols based on the white population, neglecting the differences between the races. The purpose of this study was to explore a suitable immunosuppressive regimen for Chinese renal allograft recipients.

METHODS

Two hundred cadaveric renal allograft recipients who underwent transplantation between July 1999 and October 2001 were observed. Before October 2000, 104 recipients received the conventional dose of immunosuppressants; thereafter, 96 recipients received lower dose treatment. Doses of immunosuppressive agents, the incidence of acute rejection and pulmonary infection, and patient and graft survival rates were compared between the two groups.

RESULTS

Doses of mycophenolate mofetil (MMF) and cyclosporine A (CsA) administered in the conventional dose group were significantly higher than in the lower dose group at 3 months posttransplant, as was prednisone at 6 months posttransplant. The incidence of acute rejection and subclinical rejection that was biopsy-proven or diagnosed by clinical manifestations was 17.3% and 19.8%, respectively, in the conventional dose group and the lower dose group within the first 6 months, and no significant difference was noted (P=0.55). The incidence of pulmonary infection, especially severe infection, was much higher in the conventional treatment group (40.1% and 26.9%, respectively) than that in the lower dose group (11.5% and 5.2%, respectively), and the differences were statistically significant (P<0.001). The corresponding 1-year survival rate of patients was 87.4% and 97.9% (P<0.01), and that of renal grafts was 85.5% and 96.9% (P<0.01), for patients receiving conventional dose and lower dose immunosuppressive drugs, respectively. The rate of death with a functioning allograft caused by infection in the conventional dose group was significantly higher than that in the lower dose group (12.5% vs. 0%, P<0.01).

CONCLUSIONS

The regimen of lower dose MMF, CsA, and prednisone in combination can significantly reduce the incidence of pulmonary infection, especially severe pulmonary infection, without increasing the incidence and severity of allograft rejection.

Prevalence and immunohistochemical findings of subclinical kidney allograft rejection and its association with graft outcome

Subclinical acute rejection (SAR) occurs in about 30% of stable renal transplant patients and may be a risk factor for a poor allograft outcome. In the present study, the prevalence and clinical features of subclinical rejection, and the expression of immune activation markers in surveillance graft biopsies were assessed and correlated with late graft outcomes. Protocol biopsies were obtained at 2 and 12 months post-transplant in 32 and 26 patients, respectively, with stable renal function. The Banff 1997 criteria were used for histological diagnosis. Graft function and survival and proteinuria were assessed during the 36 months of follow-up. Immunohistochemical evaluation of cell subpopulations and immunoactivation markers were performed on protocol biopsies. The prevalence of SAR at 2 months and of chronic allograft nephropathy (CAN) at 12 months in representative biopsies was 55 and 50%, respectively. Patients with SAR presented mononuclear cell infiltration with an increased expression of CD3, CD4, CD68, IL-2R and granzyme B. Kidney graft function was significantly worse in patients with SAR at 2 months who had chronic rejection on biopsy at 12 months, but SAR was not associated with a worse graft function, greater proteinuria or a lower graft survival in 3 yr of follow-up. In conclusion, we found an elevated prevalence of SAR at 2 months after transplantation with an increased expression of activation markers. Although an association of SAR with poor graft outcome was not observed, our results suggest that SAR is an immunologically active process and underscore the importance of protocol biopsies in the surveillance of transplanted kidneys.