Immune-activation gene expression in clinically stable renal allograft biopsies: molecular evidence for subclinical rejection

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.

A Rejection Gene Expression Score in Indication and Surveillance Biopsies Is Associated with Graft Outcome

Rejection-associated gene expression has been characterized in renal allograft biopsies for cause. The aim is to evaluate rejection gene expression in subclinical rejection and in biopsies with borderline changes or interstitial fibrosis and tubular atrophy (IFTA). We included 96 biopsies. Most differentially expressed genes between normal surveillance biopsies (n = 17) and clinical rejection (n = 12) were obtained. A rejection-associated gene (RAG) score was defined as its geometric mean. The following groups were considered: (a) subclinical rejection (REJ-S, n = 6); (b) borderline changes in biopsies for cause (BL-C, n = 13); (c) borderline changes in surveillance biopsies (BL-S, n = 12); (d) IFTA in biopsies for cause (IFTA-C, n = 20); and (e) IFTA in surveillance biopsies (IFTA-S, n = 16). The outcome variable was death-censored graft loss or glomerular filtration rate decline ≥ 30 % at 2 years. A RAG score containing 109 genes derived from normal and clinical rejection (area under the curve, AUC = 1) was employed to classify the study groups. A positive RAG score was observed in 83% REJ-S, 38% BL-C, 17% BL-S, 25% IFTA-C, and 5% IFTA-S. A positive RAG score was an independent predictor of graft outcome from histological diagnosis (hazard ratio: 3.5 and 95% confidence interval: 1.1–10.9; p = 0.031). A positive RAG score predicts graft outcome in surveillance and for cause biopsies with a less severe phenotype than clinical rejection.

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.

Transcriptome Analysis in Renal Transplant Biopsies Not Fulfilling Rejection Criteria

The clinical significance of renal transplant biopsies displaying borderline changes suspicious for T-cell mediated rejection (TCMR) or interstitial fibrosis and tubular atrophy (IFTA) with interstitial inflammation has not been well defined. Molecular profiling to evaluate renal transplant biopsies using microarrays has been shown to be an objective measurement that adds precision to conventional histology. We review the contribution of transcriptomic analysis in surveillance and indication biopsies with borderline changes and IFTA associated with variable degrees of inflammation. Transcriptome analysis applied to biopsies with borderline changes allows to distinguish patients with rejection from those in whom mild inflammation mainly represents a response to injury. Biopsies with IFTA and inflammation occurring in unscarred tissue display a molecular pattern similar to TCMR while biopsies with IFTA and inflammation in scarred tissue, apart from T-cell activation, also express B cell, immunoglobulin and mast cell-related genes. Additionally, patients at risk for IFTA progression can be identified by genes mainly reflecting fibroblast dysregulation and immune activation. At present, it is not well established whether the expression of rejection gene transcripts in patients with fibrosis and inflammation is the consequence of an alloimmune response, tissue damage or a combination of both.

Non-invasive messenger RNA transcriptional evaluation in human kidney allograft dysfunction

The aim of the present study was to evaluate messenger RNA expression in kidney allograft recipients. Forty-four kidney transplant recipients were evaluated up to three months after grafting. After transplantation, peripheral blood samples were drawn sequentially for real-time polymerase chain reaction analyses of perforin and TIM-3 genes. Biopsies were obtained to evaluate acute graft dysfunction and interpreted according to the Banff classification. Eight patients presented episodes of acute rejection. Recipients with rejection had significantly higher levels of TIM-3 mRNA transcripts compared to those without rejection (median gene expression 191.2 and 36.9 mRNA relative units, respectively; P<0.0001). Also, perforin gene expression was higher in patients with rejection (median gene expression 362.0 and 52.8 mRNA relative units; P<0.001). Receiver operating characteristic curves showed that the area under the curve (AUC) for the TIM-3 gene was 0.749 (95%CI: 0.670-0.827). Perforin gene mRNA expression provided an AUC of 0.699 (95%CI: 0.599 to 0.799). Overall accuracy of gene expression was 67.9% for the TIM-3 gene and 63.6% for the perforin gene. Combined accuracy was 76.8%. Negative predictive values were 95.3% for the TIM-3 gene, 95.5% for the perforin gene, and 95.4% in the combined analyses. Gene expression was significantly modulated by rejection treatment decreasing 64.1% (TIM-3) and 90.9% (perforin) compared to the median of pre-rejection samples. In conclusion, the longitudinal approach showed that gene profiling evaluation might be useful in ruling out the diagnosis of acute rejection and perhaps evaluating the efficacy of treatment.

Diagnostic Performance of Fas Ligand mRNA Expression for Acute Rejection after Kidney Transplantation: A Systematic Review and Meta-Analysis

Background

The value of Fas ligand (FASL) as a diagnostic immune marker for acute renal rejection is controversial; this meta-analysis aimed to clarify the role of FASL in acute renal rejection.

Methods

The relevant literature was included by systematic searching the MEDLINE, EMBASE, and Cochrane Library databases. Accuracy data for acute rejection (AR) and potential confounding variables (the year of publication, area, sample source, quantitative techniques, housekeeping genes, fluorescence staining, sample collection time post-renal transplantation, and clinical classification of AR) were extracted after carefully reviewing the studies. Data were analyzed by Meta-DiSc 1.4, RevMan 5.0, and the Midas module in Stata 11.0 software.

Results

Twelve relevant studies involving 496 subjects were included. The overall pooled sensitivity, specificity, positive likelihood ratio (LR), negative LR, and diagnostic odds ratio, together with the 95% CI were 0.64 (0.57–0.70), 0.90 (0.85–0.93), 5.66 (3.51–9.11), 0.30 (0.16–0.54), and 30.63 (14.67–63.92), respectively. The area under the summary receiver operating characteristic curve (AUC) was 0.9389. Fagan’s nomogram showed that the probability of AR episodes in the kidney transplant recipient increased from 15% to 69% when FASL was positive, and was reduced to 4% when FASL was negative. No threshold effect, sensitivity analyses, meta-regression, and subgroup analyses based on the potential variables had a significant statistical change for heterogeneity.

Conclusions

Current evidence suggests the diagnostic potential for FASL mRNA detection as a reliable immune marker for AR in renal allograft recipients. Further large, multicenter, prospective studies are needed to validate the power of this test marker in the non-invasive diagnosis of AR after renal transplantation.

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

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

A Meta-analysis of the Significance of Granzyme B and Perforin in Noninvasive Diagnosis of Acute Rejection After Kidney Transplantation

BACKGROUND

Previous studies have reported that granzyme B (GZMB) and perforin (PRF) could serve as noninvasive biomarkers in the diagnosis of acute rejection (AR) after kidney transplant. Yet, their noninvasive diagnostic value in clinical practice is still unknown.

METHODS

To assess the noninvasive diagnostic performance of GZMB and PRF for AR, we performed a systematic search. After reviewing published studies in which both GZMB and PRF were detected, data on the diagnostic accuracy of separate and combined evaluation of GZMB and PRF were pooled.

RESULTS

Across 16 studies (680 subjects), summary sensitivity, specificity, positive likelihood ratios, and negative likelihood ratios with 95% confidence intervals were calculated. For overall GZMB analysis, the indices were 0.76 (0.71-0.81), 0.86 (0.82-0.89), 4.58 (3.36-6.25), and 0.32 (0.22-0.47), respectively. For overall PRF analysis, the indices were 0.83 (0.78-0.88), 0.86 (0.82-0.89), 4.82 (3.66-6.35), and 0.26 (0.18-0.37), respectively. Subgroup analyses showed similar results compared to overall study analyses. In analyses of combined evaluation of GZMB and PRF, the above indices were 0.65 (0.53-0.76), 0.96 (0.91-0.98), 12.66 (5.83-27.50), and 0.40 (0.23-0.69), respectively, when both markers were positive. The probability of developing AR in kidney transplant recipients increased from 15% to 73% when both GZMB and PRF tests were positive and was reduced to 2% if that were negative.

CONCLUSIONS

Currently, neither GZMB nor PRF, if evaluated alone, could be a convincing noninvasive diagnostic marker for AR in clinical practice. Combined use of PRF and GZMB post-kidney transplant may be a better choice in AR evaluation to direct allograft biopsy execution and earlier therapeutic intervention.

Performance of polymerase chain reaction techniques detecting perforin in the diagnosis of acute renal rejection: a meta-analysis

Background

Studies in the past have shown that perforin expression is up-regulated during acute renal rejection, which provided hopes for a non-invasive and reliable diagnostic method to identify acute rejection. However, a systematic assessment of the value of perforin as a diagnostic marker of acute renal rejection has not been performed. We conducted this meta-analysis to document the diagnostic performance of perforin mRNA detection and to identify potential variables that may affect the performance.

Methodology/Principal Findings

Relevant materials that reported the diagnostic performance of perforin mRNA detection in acute renal rejection patients were extracted from electronic databases. After careful evaluation of the studies included in this analysis, the numbers of true positive, true negative, false positive and false negative cases of acute renal rejection identified by perforin mRNA detection were gathered from each data set. The publication year, sample origin, mRNA quantification method and housekeeping gene were also extracted as potential confounding variables. Fourteen studies with a total of 501 renal transplant subjects were included in this meta-analysis. The overall performance of perforin mRNA detection was: pooled sensitivity, 0.83 (95% confidence interval: 0.78 to 0.88); pooled specificity, 0.86 (95% confidence interval: 0.82 to 0.90); diagnostic odds ratio, 28.79 (95% confidence interval: 16.26 to 50.97); and area under the summary receiver operating characteristic curves value, 0.9107±0.0174. The univariate analysis of potential variables showed some changes in the diagnostic performance, but none of the differences reached statistical significance.

Conclusions/Significance

Despite inter-study variability, the test performance of perforin mRNA detected by polymerase chain reaction was consistent under circumstances of methodological changes and demonstrated both sensitivity and specificity in detecting acute renal rejection. These results suggest a great diagnostic potential for perforin mRNA detection as a reliable marker of acute rejection in renal allograft recipients.

Cytokine gene expression in peripheral blood mononuclear cells during acute renal allograft rejection

Many studies have explored the participation of cytokines and their genes in renal allograft rejection by using biopsy tissues. To screen for rejection, a biopsy is too invasive to perform without a clinical clue. Therefore, we studied the expression of cytokines that contribute to the early phase of allograft rejection by analyzing mRNA transcripts in sequential blood samples of peripheral blood mononuclear cells (PBMCs) 120 of 6 among patients transplanted before diagnosis of rejection. for comparison with 6 control recipients. The relative expression amount of cytokine genes encoding interleukin (IL) 2, IL-4, IL-10, IL-15, and interferon-γ were assessed using real-time reverse-transcription polymerase chain reactions. IL-2, IL-4, and IL-15 mRNA expressions in clinically stable prerejection phase of the rejection group were significantly higher than those of the control group. In the prerejection samples, the expression of mRNA encoding IL-10 negatively correlated with the expressions of IL-2, IL-4, and IL-15 mRNAs, which were not different from the positive correlations in the postoperative samples from the control group. The expression patterns of IL-2, IL-4, IL-10, and IL-15 genes in PBMCs after transplantation may help to identify acute rejection episodes before clinical deterioration to monitor the efficacy of immunosuppressive treatment.

Surveillance biopsies in children post-kidney transplant

Surveillance biopsies are increasingly used in the post-transplant monitoring of pediatric renal allograft recipients. The main justification for this procedure is to diagnose early and presumably modifiable acute and chronic renal allograft injury. Pediatric recipients are theoretically at increased risk for subclinical renal allograft injury due to their relatively large adult-sized kidneys and their higher degree of immunological responsiveness. The safety profile of this procedure has been well investigated. Patient morbidity is low, with macroscopic hematuria being the most common adverse event. No patient deaths have been attributed to this procedure. Longitudinal surveillance biopsy studies have revealed a substantial burden of subclinical immunological and non-immunological injury, including acute cellular rejection, interstitial fibrosis and tubular atrophy, microvascular lesions and transplant glomerulopathy. The main impediment to the implementation of surveillance biopsies as the standard of care is the lack of demonstrable benefit of early histological detection on long-term outcome. The considerable debate surrounding this issue highlights the need for multicenter, prospective, and randomized studies.

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.

Noninvasive Tim-3 messenger RNA evaluation in renal transplant recipients with graft dysfunction

BACKGROUND

Renal biopsies are usually needed to elucidate graft dysfunction. In this study, T-cell immunoglobulin domain, mucin domain mRNA expression in the peripheral blood leukocytes (PBL) and urinary cells (UC) were studied as a noninvasive method for the diagnosis of acute rejection (AR) of kidney transplant patients with dysfunction.

METHODS

One hundred sixty biopsies were obtained from 115 patients. Blood and urine samples were collected immediately before the biopsies. Histopathologic diagnoses were acute tubular necrosis with superimposed AR or acute tubular necrosis in patients with delayed graft function (DGF), and (AR), or calcineurin inhibitor nephrotoxicity (CIN), or interstitial fibrosis and tubular atrophy in patients with acute graft dysfunction (AGD). Fifteen protocol biopsies of stable grafts were used as controls. mRNA relative quantification was performed by real-time polymerase chain reaction.

RESULTS

Gene expression in tissue, PBL, and UC was always higher in patients with AR than in patients with the other causes of graft dysfunction (P<0.001). Significant correlations of gene expression in different compartments were observed (P<0.001). The obtained diagnostic parameters were 100% accurate in the DGF group and, respectively, for blood and urine: sensitivity (87% and 84%); specificity (95% and 96%); positive predictive value (87% and 89%); negative predictive value (93% and 94%); and accuracy (91% and 93%) for the group of patients with AGD.

CONCLUSION

T-cell immunoglobulin domain, mucin domain mRNA quantification by real-time polymerase chain reaction in PBL and UC of renal transplant patients undergoing DGF or AGD may become a useful tool for an accurate noninvasive diagnosis of AR.

Intragraft mRNA cytotoxic molecule expression in renal allograft recipients

The gene expression of the cytotoxic T-cell molecules perforin, granzyme B and Fas ligand are associated with acute rejection in renal allograft recipients. Several immune mechanisms are linked to severe systemic inflammation in brain-dead organ donors. We examined the mRNA expression of these T-cell activation biomarkers in donor kidney biopsies to evaluate if they could separate living from deceased donors and primary graft function from delayed graft function or acute rejection in the early post transplantation period. We obtained 139 cadaveric and 19 living donor kidney core biopsies post reperfusion and 78 renal allograft biopsies taken because of graft dysfunction. RNA was isolated from tissue samples and mRNA encoding perforin, granzyme B or Fas ligand and a constitutively expressed cyclophilin B, a reference gene, was measured with the use of real-time quantitative polymerase chain reaction assay, and the levels of expression was correlated with allograft status. We did not find statistically significant differences in gene expression of perforin, granzyme B or Fas ligand among deceased and living donor kidneys and the mRNA expression of these cytotoxic molecules in donor kidney biopsies did not distinguish primary allograft function or early acute rejection. Significant differences were found between acute rejection (n=17) and zero-hour samples and acute rejection and non-rejection (n=41) samples for all 3 measured transcripts. No significant difference was found between acute borderline rejection (n=16) and non-rejection samples. In conclusion, effector molecules secreted by cytotoxic T lymphocytes were not activated in deceased donor kidneys and the genes did not classify the post-transplant course.

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.

Long-term outcome of early steroid withdrawal after kidney transplantation in African American recipients monitored by surveillance biopsy

Generally chronic steroid therapy is standard care for African American (AA) kidney recipients because of their higher incidence of rejections and lower long-term graft survival. This prospective study evaluated the long-term safety and efficacy of early steroid withdrawal (ESW) in AA recipients. A total of 206 recipients were studied; 103 AA and 103 non-AA recipients monitored by serial surveillance biopsies from 1 to 60 months posttransplantation to evaluate subclinical acute rejections (SCAR) and chronic allograft injury (CAI). Biopsy-proven clinical acute rejections (BPAR) and SCAR were treated. Primary end point was BPAR and secondary end points were 5-year SCAR, CAI and survival. Incidences of BPAR was 16% versus 14% (p = 1.0), prevalence of CAI due to hypertension was 48% versus 30% (p = 0.05) and interstitial fibrosis/tubular atrophy was 47% versus 32% (p = 0.05) and the mean serum creatinine levels were 2.1 versus 1.8 mg/dL (p = 0.05) at 5-years in AA versus non-AA recipients. The incidence of SCAR was 23% versus 11% at 1 month (p = 0.04), 12% versus 3% at 3 years (p = 0.04) and 10% versus 1% at 5 years (p = 0.04) in AA and non-AA recipients, respectively. Five-year patient survivals were 81% and 88% (p = 0.09) and graft survivals were 71% and 73%(p = 0.19) in AA and non-AA groups, respectively. After early steroid withdrawal AA kidney recipients have significantly lower renal function and higher SCAR and CAI but 5-year graft survival are comparable to non-AA recipients.

Subclinical Rejection in the Initial Postoperative Period in Small Intestinal Transplantation: A Negative Influence on Graft Survival

BACKGROUND

Subclinical rejection (SCR) is a known entity in various solid organ transplants but not in intestinal transplantation.

METHODS

The purpose of this study is to characterize the presence and effect of SCR in small intestinal transplantation (Itx). A total of 151 patients who underwent Itx and maintained a functioning graft for at least 3 months after Itx were investigated. The clinicopathological characteristics associated with a SCR episode within 3 months after Itx were analyzed. Cox regression with the landmark method (the landmark time being 3 months after Itx) was used for the analyses of overall graft survival and cause-specific hazard rate of SCR.

RESULTS

A total of 2744 small intestinal transplant biopsies within 3 months after Itx were available for retrospective evaluation; 171 cases (6.2%) were determined as SCR and 78 patients (51.7%) experienced SCR episode within 3 months after Itx. Adult patients were associated with a significantly higher occurrence of a SCR episode (P=0.001). Overall graft survival at 5 years posttransplant for patients experiencing SCR within 3 months posttransplant and for patients without SCR was 37.2% and 60.2%, respectively (P=0.009). Cause-specific hazard rate analysis showed that a SCR episode was associated with a significantly higher hazard rate of death due to infection (P=0.005).

CONCLUSIONS

A SCR episode in the initial postoperative period of Itx is a significant factor for unfavorable graft prognosis, likely representing alloimmune injury ultimately resulting in patient morbidity due to infection.

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.

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.

Chronic allograft nephropathy: current concepts and future directions

The paradigm that chronic rejection causes all progressive late allograft failure has been replaced by a hypothesis of cumulative damage, where a series of time-dependent immune and nonimmune mechanisms injure the kidney and lead to chronic interstitial fibrosis and tubular atrophy, representing a final common pathway of injury and its consequent fibrotic healing response. Allograft damage is common, progressive, time-dependent, clinically important and modified by immunosuppression. Early after transplantation, tubulointerstitial damage is predominantly related to ischemia reperfusion injury, acute tubular necrosis, acute and subclinical rejection and/or calcineurin inhibitor nephrotoxicity, superimposed on preexisting donor disease. Later, cellular inflammation lessens and is replaced by microvascular and glomerular injury from calcineurin inhibitor nephrotoxicity, hypertension, immune-mediated fibrointimal vascular hyperplasia, transplant glomerulopathy and capillary injury, polyoma virus and/or recurrent glomerulonephritis. Additional mechanisms of injury include internal architectural disruption of the kidney, cortical ischemia, persistent chronic inflammation, replicative senescence, cytokine excess and fibrosis induced by epithelial-to-mesenchymal transition. Current understanding of the etiology, pathophysiology and evolution of pathological changes are detailed. An approach to histological assessment of the individual failing graft are presented and a series of postulates are defined for future studies of chronic allograft nephropathy.

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.

Quantitative detection of changes in cytokine gene expression in peripheral blood mononuclear cells correlates with and precedes acute rejection in renal transplant recipients

Immunological monitoring of transplant recipients is an attractive concept. Cytokines provide an obvious focus for research, as they are central to the human immune response. This study aimed to identify cytokines whose sequential gene expression differentiated rejectors from non-rejectors immediately following renal transplantation. Forty-five renal transplant recipients (15 rejectors) and 13 living donors were recruited. Total RNA was extracted from the peripheral blood mononuclear cells and reverse transcribed. Cytokine gene expression levels of IL-4, IL-10, TNF-alpha and TGF-beta1 were measured using TaqMan. IL-10 expression increased significantly following donor surgery. IL-4 and TNF-alpha patterns clearly differentiated between rejectors and non-rejectors. In the rejectors significant increases occurred more than 48 h before clinical graft dysfunction. Negative predictive values were 76% and 80% for IL-4 and TNF-alpha, respectively. This study has identified two cytokines (IL-4 and TNF-alpha) whose gene expression patterns differentiate between rejecting and non-rejecting renal transplant recipients making immunological monitoring possible.

Functionally significant renal allograft rejection is defined by transcriptional criteria

Renal allograft acute cellular rejection (ACR) is a T-cell mediated disease that is diagnosed histologically. However, many normally functioning allografts have T-cell infiltrates and histological ACR, and many nonimmune processes cause allograft dysfunction. Thus, neither histological nor functional criteria are sufficient to establish a significant rejection, and the fundamental features of clinical rejection remain undefined. To differentiate allograft lymphocyte infiltration from clinically significant ACR, we compared renal biopsies from patients with ACR to patients with: sub-clinical rejection (SCR, stable function with histological rejection); no rejection; and nontransplanted kidneys. Biopsies were compared histologically and transcriptionally by RT-PCR for 72 relevant immune function genes. Neither the degree nor the composition of the infiltrate defined ACR. However, transcripts up-regulated during effector T(H)1 T-cell activation, most significantly the transcription factor T-bet, the effector receptor Fas ligand and the costimulation molecule CD152 clearly (p = 0.001) distinguished the patient categories. Transcripts from other genes were equivalently elevated in SCR and ACR, indicating their association with infiltration, not dysfunction. Clinically significant ACR is not defined solely by the magnitude nor composition of the infiltrate, but rather by the transcriptional activity of the infiltrating cells. Quantitative analysis of selected gene transcripts may enhance the clinical assessment of allografts.

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.

Delta analysis of posttransplantation tubulointerstitial damage

BACKGROUND

Chronic interstitial fibrosis (CIF) is an adverse prognostic feature of chronic allograft nephropathy.

METHODS

We evaluated the evolution, onset, potential causes, and outcomes of tubulointerstitial damage using 959 protocol kidney biopsy specimens obtained regularly until 10 years after transplantation. Specimens were scored by the Banff schema and analyzed for time-specific change or "delta damage" from sequential biopsy-pairs (n=839).

RESULTS

Substantial CIF occurred within 1 year after transplantation, comprising 67.6% of the total burden accumulated during the study period. The maximal intensity of CIF formation occurred within the first 3 months, as a result of acute tubular necrosis and acute and subclinical rejection (all P<0.05), where fibrosis rates exceeded loss from tubular atrophy. By 1 year, diminished CIF formation was accompanied by declining low-level subclinical inflammation (P<0.001) and increasingly prevalent calcineurin inhibitor nephrotoxicity (P<0.01). Banff CIF correlated with tubular atrophy (r=0.82, P<0.001), with tubulointerstitial damage showing a cumulative and irreversible pattern. Mononuclear cell infiltration within areas of tubulointerstitial damage correlated with CIF (r=0.49, P<0.001), tubular atrophy (r=0.43, P<0.001), and Banff i scores (r=0.34, P<0.001) and, most importantly, heralded histologic progression (P<0.001). CIF formation preceded and correlated with glomerulosclerosis (r=0.40, P<0.001), although isotopic glomerular filtration rates underestimated the severity of tubular damage. Cyclosporine (vs. tacrolimus, P<0.001) increased delta CIF, and mycophenolate was protective (vs. azathioprine, P<0.001), independent of their immunosuppressive and nephrotoxic properties when assessed by multivariate analysis of biopsy-pairs (n=849).

CONCLUSION

CIF was a result of early ischemia-reperfusion injury, acute, subacute or persistent interstitial inflammation occurring in a time-dependent manner and was considerably modified by immunosuppressive therapy.

Kidney transplant rejection and tissue injury by gene profiling of biopsies and peripheral blood lymphocytes

A major challenge for kidney transplantation is balancing the need for immunosuppression to prevent rejection, while minimizing drug-induced toxicities. We used DNA microarrays (HG-U95Av2 GeneChips, Affymetrix) to determine gene expression profiles for kidney biopsies and peripheral blood lymphocytes (PBLs) in transplant patients including normal donor kidneys, well-functioning transplants without rejection, kidneys undergoing acute rejection, and transplants with renal dysfunction without rejection. We developed a data analysis schema based on expression signal determination, class comparison and prediction, hierarchical clustering, statistical power analysis and real-time quantitative PCR validation. We identified distinct gene expression signatures for both biopsies and PBLs that correlated significantly with each of the different classes of transplant patients. This is the most complete report to date using commercial arrays to identify unique expression signatures in transplant biopsies distinguishing acute rejection, acute dysfunction without rejection and well-functioning transplants with no rejection history. We demonstrate for the first time the successful application of high density DNA chip analysis of PBL as a diagnostic tool for transplantation. The significance of these results, if validated in a multicenter prospective trial, would be the establishment of a metric based on gene expression signatures for monitoring the immune status and immunosuppression of transplanted patients.

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.

Splicing alterations in human renal allografts: detection of a new splice variant of protein kinase Par1/Emk1 whose expression is associated with an increase of inflammation in protocol biopsies of transplanted patients

Protein kinase Emk1/Par1 (GenBank accession no. X97630) has been identified as a regulator of the immune system homeostasis. Since immunological factors are critical for the development of chronic allograft nephropathy (CAN), we reasoned that expression of Par1/Emk1 could be altered in kidney allografts undergoing CAN. In this paper, we have analysed the association among renal allograft lesions and expression of Par1/Emk1, studied by RT-PCR on total RNA from 51 protocol biopsies of transplanted kidneys, five normal kidneys, and five dysfunctional allografts. The most significant result obtained has been the detection of alterations in the normal pattern of alternative splicing of the Par1/Emk1 transcript, alterations that included loss of expression of constitutively expressed isoforms, and the inclusion of a cryptic exon to generate a new Emk1 isoform (Emk1C). Expression of Emk1C was associated with an increase in the extension of the interstitial infiltrate (0.88+/-0.33 in Emk1C([+]) vs. 0.41+/-0.50 in Emk1C([-]); P<0.011), and with a trend to display higher interstitial scarring (0.66+/-0.70 vs. 0.29+/-0.52; P=0.09) in protocol biopsies when evaluated according to the Banff schema. Moreover, a higher mean arterial pressure (MAP) was also observed (110+/-11 vs. 99+/-11 mm Hg; P=0.012). From these results we propose that Par1/Emk1 could have a role in the development of CAN in kidney allografts.

Subclinical rejection and borderline changes in early protocol biopsy specimens after renal transplantation

BACKGROUND

To determine the significance of early subclinical rejection, we reviewed protocol biopsies performed on days 7 and 28 during a 4-year period.

METHODS

The study was confined to patients (n=115) with stable graft function at the time of biopsy; 76 adequate biopsies at day 7 and 79 at day 28 were performed.

RESULTS

At day 7, 10 biopsy specimens (13%) showed acute rejection (AR) and 9 (12%) showed borderline changes. Eight of 10 patients with AR received immediate pulsed methylprednisolone (MP) and one untreated patient developed clinical rejection (CR) within 3 days. Four of nine patients whose biopsy specimens showed borderline changes received MP and three untreated patients developed CR within 3 days. At day 28, six biopsy specimens (8%) showed AR and 13 (16%) showed borderline changes. Three of six patients with AR received immediate pulsed MP and one untreated patient developed CR within 6 days. Ten of 13 patients with borderline changes had been treated for AR in the previous 3 weeks. Twelve patients with subclinical rejection or borderline changes at day 28 were never subsequently treated for rejection, and outcome at 6 years did not differ from those patients whose biopsy specimens showed no rejection.

CONCLUSIONS

Compared with some units, the incidence of subclinical rejection is low. The majority of untreated subclinical borderline changes and rejection at day 7 behaved as early clinical rejections and at day 28 as resolving clinical rejections. Untreated subclinical rejection or borderline change at day 28 was not an adverse prognostic factor for long-term outcome.

Molecular markers in subclinical acute rejection of renal transplants

In this study, we evaluated the expression of molecular markers of acute rejection in protocol biopsies of patients with and without subclinical acute rejection (SAR). Protocol biopsies were performed at 2 months (n = 21) and 12 months (n = 14) after kidney transplantation in patients with stable allograft function. After biopsy tissue RNA isolation, reverse transcription and polymerase chain reaction (RT-PCR) for the glyceraldehyde 3-phospate dehydrogenase (GAPDH), perforin, granzyme B and Fas ligand genes were performed. The Banff 97 classification was used for histological diagnosis. Creatinine concentrations at 2 months were significantly higher in patients with SAR (1.46 +/- 0.27 x 1.18 +/- 0.24; p < 0.02). Perforin transcripts were found in 15 biopsy specimens, 10 of which had histological signs of SAR (p = 0.06). Granzyme B expression was found in 10 specimens, nine of which had SAR (p < 0.01). Fas ligand was expressed in seven specimens, and six of them were classified as SAR (p < 0.01). Perforin expression had the highest sensitivity (81%) for the diagnosis of SAR. Granzyme B and Fas ligand had specificity of 90%. At 12 months, there was no significant difference in creatinine concentrations for patients with and without previous SAR (1.63 +/- 0.57 x 1.28 +/- 0.31; p = 0.10). Molecular analysis revealed that there was no statistically significant difference in the expression of perforin and granzyme B in patients with and without SAR. Fas ligand expression was observed in five samples, four of which had histological signs of SAR (p = 0.03). At 12 months, perforin expression had the highest sensitivity (83%), and Fas ligand, the highest specificity (88%) for the diagnosis of SAR. We concluded that the expression of genes that encode proteins involved in the cytolytic attack against the allograft is increased in kidneys with SAR. These findings support the understanding that SAR is an active immune process potentially deleterious to renal allografts.

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.

House keeping genes and gene expression analysis in transplant recipients: a note of caution

BACKGROUND

House keeping genes are often used as a means of standardising results obtained in gene expression investigations. This study was performed to investigate whether beta-actin, beta2-microglobulin (two genes frequently quoted as house keeping genes) and/or transferrin receptor would be suitable house keeping genes for use in gene expression analysis of renal transplant recipients.

METHODS

Sequential expression of all three genes was measured in the peripheral blood mononuclear cells of 13 living donors and 45 renal transplant recipients, pre-operatively and then daily for up to 2 weeks. Fifteen of the recipients experienced an episode of biopsy proven acute rejection. Gene expression measurement was performed using quantitative real time 'TaqMan' PCR technology.

RESULTS

Gene expression of all three genes was unchanged in the living donor cohort. However, in the transplant recipients there were significant increases in expression following transplantation in the non-rejectors, and preceding the diagnosis of acute rejection. In the latter group, levels returned to pre-transplant values after the commencement of anti-rejection therapy.

CONCLUSIONS

Beta-actin, beta2-microglobulin and transferrin receptor gene expression, although not influenced by surgery, is influenced by transplantation, acute rejection and anti-rejection therapy making these genes unsuitable as house keeping genes following renal transplantation. These findings may cast doubt on the results of some studies that used these genes for the purposes of standardisation when looking at cDNA measurement. We suggest that any group wishing to use a house keeping gene ensure that its expression is independent of study parameters prior to the start of the study.

Serial peripheral blood perforin and granzyme B gene expression measurements for prediction of acute rejection in kidney graft recipients

In the present study we investigated whether peripheral blood gene expression measurements may serve as an early and non-invasive tool to predict renal allograft rejection. Peripheral blood was collected twice weekly after transplantation and gene expression was measured using real-time polymerase chain reaction (PCR). Recipients with acute rejection (n = 17) had higher levels of perforin and granzyme B transcript on days 5-7, 8-10, 11-13, 17-19, 20-22, and 26-29, as compared to patients without rejection (n = 50, p < 0.05 in all cases). Rejection diagnosis using gene expression criteria, determined with receiver operating characteristic (ROC) curves, was possible 2-30 days before traditional diagnosis (median 11 days). The best diagnostic result was obtained from samples taken on days 8-10, with a specificity of 90% and a sensitivity of 82% for perforin, and a specificity of 87% and sensitivity of 72% for granzyme B. Decreases in perforin (p < 0.01) and granzyme B expression (p < 0.05) were observed after initiation of anti-rejection therapy. Our data indicate that gene expression measurement is a useful tool for the recognition of graft rejection in its earliest stages. Serial measurements could be implemented as a monitoring system to highlight patients at higher risk of rejection, making them candidates for biopsy or pre-emptive anti-rejection therapy.

The impact of repeated subclinical acute rejection on the progression of chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is due to both immunologic and non-immunologic factors and results in the development of nonspecific pathologic features that may even be present in long-term well-functioning renal allografts. To investigate the natural history of CAN and potential risk factors associated with progression of these histologic lesions, this study evaluated the of histologic alterations of 124 sequential protocol biopsies performed at 2, 3, and 5 yr after transplantation in 46 patients who exhibited histologic evidence of CAN in the 1-yr biopsy. The occurrence of late acute rejection (AR) greater than 4 mo posttransplant was significantly associated with the development of histologic CAN. In contrast, early clinical AR occurring within 3 mo had no impact on the subsequent development of CAN at 1 yr. Subclinical AR was evident in association with CAN in 50%, 32%, 19%, and 16% of cases with CAN at 1, 2, 3, and 5 yr, respectively. These acute lesions correlated significantly with histologic progression defined as an increased CADI score of the follow-up biopsies. Furthermore, a group of patients who exhibited repeated subclinical AR in the sequential follow-up biopsies had a lower creatinine clearance at 5 yr after transplantation and worse long-term graft survival. In contrast, the absence of evidence of acute inflammation in association with CAN at any time point was associated with minimal deterioration in renal function or progression of renal lesions during the observation period. These results suggest that the persistence of chronic active inflammation may be responsible for the histologic progression of CAN.

Comparative evaluation of 'TaqMan' RT-PCR and RT-PCR ELISA for immunological monitoring of renal transplant recipients

By sequentially monitoring cytokine gene expression (using RT-PCR ELISA technology) in peripheral blood cells of renal transplant recipients in the early post-operatively period we have shown that expression patterns correlate with clinical events, namely acute allograft rejection. This strategy may have the potential of predicting acute rejection prior to clinical detection. Unfortunately, the technique used was time consuming and only semi-quantitative and, therefore, not suitable for clinical application. In this study, we have sought to confirm the results of the early work using a real time quantitative RT-PCR technique ('TaqMan'), which may be applicable in the clinical laboratory. 'TaqMan' primers and probes were designed for Interleukin (IL)-4 and IL-10 using Primer Express software. Cytokine gene expression for both cytokines was re-measured in stored cDNA samples from 27 non-rejectors and 14 patients experiencing an episode of biopsy proven acute rejection. Compared to pre-transplant levels, IL-4 gene expression fell significantly on post-operative days 2 and 7 before returning to baseline values by day 14 in the non-rejectors. In the rejectors, the initial significant fall was again seen, but with an earlier return to pre-transplant levels at the time of rejection diagnosis. This was followed by a further significant fall in levels 48 h after the initiation of anti-rejection therapy. These different patterns for rejectors and non-rejectors were seen using both techniques. For IL-10, gene expression increased significantly following transplantation throughout the study period when compared to baseline values. This pattern was seen using both techniques. In the rejectors, there were different patterns seen depending on the technique used. When using RT-PCR ELISA, the initial rise was again seen followed by a return to baseline values at the time of rejection diagnosis followed by a further significant rise in gene expression after the start of anti-rejection treatment. The pattern resembled those of the non-rejectors when expression was measured using 'TaqMan'. This study has confirmed that sequential monitoring of cytokine gene expression, measured in peripheral blood mononuclear cells, detects significant changes that correlate with clinical events in renal transplant recipients, including acute rejection, although not all changes detected with RT-PCR ELISA were confirmed. Therefore, real time quantitative RT-PCR technology may be useful in monitoring the immunological status of these patients in the early post-operative period.

Heightened peripheral blood lymphocyte CD69 expression is neither sensitive nor specific as a noninvasive diagnostic test for renal allograft rejection

It has been reported that acute allograft rejection is associated with heightened expression of the peripheral blood lymphocyte (PBL) early activation marker CD69 and that this may serve as a potential biomarker of rejection. This study sought to determine whether PBL CD69 expression correlates with both acute clinical and subclinical renal allograft rejection as well as clinically inapparent cytomegalovirus (CMV) infection. Flow cytometric determination of PBL CD69 expression was performed at the time of clinical and protocol biopsies (n = 131) in 45 renal transplant recipients. Nineteen patients also underwent weekly monitoring of PBL CD69 expression for the initial 15 wk after transplantation. Simultaneous screening for CMV viremia was performed with a semiquantitative PCR assay. No differences were seen in either CD4+ or CD8+ lymphocyte CD69 expression between the biopsy diagnoses. CMV viremia however, independent of rejection, was associated with greater CD69 expression on CD8+ lymphocytes (17.8 +/- 10.4% versus 9.6 +/- 4.8%; P < 0.0001) but not CD4+ lymphocytes. No individuals experienced clinical CMV disease. Weekly monitoring of PBL CD69 expression did not change coincident with the diagnosis of rejection; however, CMV viremia coincided with a substantial rise in the proportion of CD8+69+ lymphocytes in a number of individuals. Thus, PBL CD69 expression is neither sensitive nor specific for the noninvasive diagnosis of renal allograft rejection. Furthermore, clinically inapparent CMV viremia is associated with heightened expression of this activation marker on CD8+ lymphocytes. This latter finding suggests that clinically inapparent CMV viremia may be a potential confounder for biomarkers of rejection that examine peripheral blood lymphocytes.

Molecular and immunohistochemical characterization of the onset and resolution of human renal allograft ischemia-reperfusion injury

BACKGROUND Following allotransplantation, renal ischemia-reperfusion (I/R) injury initiates a series of events that provokes counter-adaptive immunity. Though T cells clearly mediate allospecific immunity, the manner in which reperfusion events augment their activation has not been established. In addition, comprehensive analysis of I/R injury in humans has been limited. METHODS To evaluate the earliest events occurring following allograft reperfusion and gain insight into those factors linking reperfusion to alloimmunity, we examined human renal allografts 30 to 60 minutes postreperfusion (n=10) and compared them with allografts with normal function that had resolved their I/R injury insult (>1 month posttransplant, n=6) and to normal kidneys (living donor kidneys before procurement, n=8). Biopsies were processed both for immunohistochemical analysis as well as for transcript analysis by real-time quantitative polymerase chain reaction (RT-PCR). RESULTS Reperfusion injury was characterized by increased levels of gene transcripts known to be involved in cellular adhesion, chemotaxis, apoptosis, and monocyte recruitment and activation. T-cell-associated transcripts were generally absent. However, recovered allografts exhibited increased levels of T-cell and costimulation-related gene transcripts despite normal allograft function. Consistent with these findings, the immediate postreperfusion state was characterized histologically by tubular injury and monocyte infiltration, while the stable posttransplant state was notable for T-cell infiltration. CONCLUSIONS These data suggest that monocytes and transcripts related to their recruitment dominate the immediate postreperfusion state. This gives way to a T-cell dominant milieu even in grafts selected for their stable function and absence of rejection. These data have implications for understanding the fundamental link between I/R injury and alloimmunity.

Granzyme expression in fine-needle aspirates from liver allografts is increased during acute rejection

We investigated whether determination in fine-needle aspiration biopsy (FNAB) specimens of cells expressing granzymes (Grs) and Fas ligand would provide a reliable, easy, and quantitative measure of rejection activity in the transplanted liver. Retrospectively, 13 FNAB specimens obtained during clinical acute rejection, 10 FNAB specimens obtained during subclinical rejection, 12 FNAB specimens obtained during cytomegalovirus (CMV) infection, and 26 FNAB specimens obtained in the absence of rejection or infection were included on the study. Cytospin preparations of FNAB and peripheral-blood specimens were immunocytochemically stained for Fas-ligand and Gr, and increments in the liver were calculated by subtracting frequencies of positive cells in blood from those in FNAB specimens. Only sporadically Fas ligand-expressing, but many Gr-expressing, cells were detected in FNAB specimens. Increments in Gr-positive (Gr(+)) cells were significantly greater in FNAB specimens obtained during clinical rejection (median, 70 Gr(+) cells; range, 0 to 312 Gr(+) cells; P = .006) and tended to be greater in FNAB specimens obtained during subclinical rejection (median, 62 Gr(+) cells; range, 5 to 113 Gr(+) cells; P = .09) compared with those obtained in the absence of rejection (median, 16 Gr(+) cells; range, 0 to 103 Gr(+) cells). Increments obtained during clinical or subclinical rejection did not differ from those obtained during CMV infection (median, 27 Gr(+) cells; range, 6 to 212 Gr(+) cells). With the exclusion of specimens obtained during CMV infection, the sensitivity of Gr determination in FNAB specimens for the diagnosis of acute rejection (either clinical or subclinical) was 70%, and specificity, 69%. In FNAB specimens obtained during clinical and subclinical acute rejection episodes after liver transplantation, increased numbers of Gr-expressing cells were present; in the absence of CMV infection, their quantification provides a measure for rejection activity with moderate accuracy.