Banff 07 classification of renal allograft pathology: updates and future directions

FOXP3-enriched infiltrates associated with better outcome in renal allografts with inflamed fibrosis

BACKGROUND

FOXP3-expressing regulatory T cells (Tregs) play a crucial role in maintaining allogeneic transplant tolerance in experimental models. In clinical transplantation, there are few data about their role in chronic inflammation. We hypothesized that Tregs might accumulate within the graft since enrichment of Tregs has been frequently described in chronically inflamed tissues.

METHODS

Sixty-seven biopsies, indicated by a rise in creatinine level, were studied. Thirty-four biopsies showing acute T-cell-mediated rejection and 33 displaying inflamed fibrosis were selected. Tregs frequency was calculated for each infiltrate by counting FOXP3+ and CD3+ cells on two contiguous serial sections.

RESULTS

A total of 121 infiltrates were scored with a mean of 309 CD3+ cells per infiltrate (range: 50-700). Tregs were enriched within allografts exhibiting inflamed fibrosis versus acute cellular rejection (10.6 +/- 6.8% versus 5.5 +/- 2.6%, respectively, P = 0.005). In those with inflammation within scarred areas, the subset of patients with a low FOXP3/CD3 ratio (below the median value) displayed a lower frequency of B-cell-enriched nodular cell clusters (20% versus 86%, P = 0.001) and had a significantly lower graft survival (log-rank, P = 0.02). In multivariate analysis, the low FOXP3/CD3 ratio remained an independent indicator of outcome (P = 0.03). Consistently, the FOXP3+/IL-17+ cell ratio was higher in nodular than in diffuse infiltrates.

CONCLUSIONS

Our results suggest that Tregs may dampen the graft injury in chronic (versus acute) inflammation and stress the importance of devising strategies to enhance Tregs efficiency.

Correlation of donor-specific antibodies, complement and its regulators with graft dysfunction in cardiac antibody-mediated rejection

Antibody-mediated rejection (AMR) is an immunopathologic process in which activation of complement often results in allograft injury. This study correlates C4d and C3d with HLA serology and graft function as diagnostic criteria for AMR. Immunofluorescence staining for C4d and C3d was performed on 1511 biopsies from 330 patients as part of routine diagnostic work-up of rejection. Donor-specific antibodies were detected in 95% of those with C4d+C3d+ biopsies versus 35% in the C4d+C3d- group (p = 0.002). Allograft dysfunction was present in 84% in the C4d+ C3d+ group versus 5% in the C4d+C3d- group (p < 0.0001). Combined C4d and C3d positivity had a sensitivity of 100% and specificity of 99% for the pathologic diagnosis of AMR and a mortality of 37%. Since activation of complement does not always result in allograft dysfunction, we correlated the expression pattern of the complement regulators CD55 and CD59 in patients with and without complement deposition. The proportion of patients with CD55 and/or CD59 staining was highest in C4d+C3d- patients without allograft dysfunction (p = 0.03). We conclude that a panel of C4d and C3d is diagnostically more useful than C4d alone in the evaluation of AMR. CD55 and CD59 may play a protective role in patients with evidence of complement activation.

Feto-placental adaptations to maternal obesity in the baboon

Maternal obesity is present in 20-34% of pregnant women and has been associated with both intrauterine growth restriction and large-for-gestational age fetuses. While fetal and placental functions have been extensively studied in the baboon, no data are available on the effect of maternal obesity on placental structure and function in this species. We hypothesize that maternal obesity in the baboon is associated with a maternal inflammatory state and induces structural and functional changes in the placenta. The major findings of this study were: 1) decreased placental syncytiotrophoblast amplification factor, intact syncytiotrophoblast endoplasmic reticulum structure and decreased system A placental amino acid transport in obese animals; 2) fetal serum amino acid composition and mononuclear cells (PBMC) transcriptome were different in fetuses from obese compared with non-obese animals; and 3) maternal obesity in humans and baboons is similar in regard to increased placental and adipose tissue macrophage infiltration, increased CD14 expression in maternal PBMC and maternal hyperleptinemia. In summary, these data demonstrate that in obese baboons in the absence of increased fetal weight, placental and fetal phenotype are consistent with those described for large-for-gestational age human fetuses.

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.

Scoring total inflammation is superior to the current Banff inflammation score in predicting outcome and the degree of molecular disturbance in renal allografts

Emerging molecular analysis can be used as an objective and independent assessment of histopathological scoring systems. We compared the existing Banff i-score to the total inflammation (total i-) score for assessing the molecular phenotype in 129 renal allograft biopsies for cause. The total i-score showed stronger correlations with microarray-based gene sets representing major biological processes during allograft rejection. Receiver operating characteristic curves showed that total-i was superior (areas under the curves 0.85 vs. 0.73 for Banff i-score, p = 0.012) at assessing an abnormal cytotoxic T-cell burden, because it identified molecular disturbances in biopsies with advanced scarring. The total-i score was also a better predictor of graft survival than the Banff i-score and essentially all current diagnostic Banff categories. The exception was antibody-mediated rejection which is able to predict graft loss with greater specificity (96%) but at low sensitivity (38%) due to the fact that it only applies to cases with this diagnosis. The total i-score is able to achieve moderate sensitivities (60-80%) with losses in specificity (60-80%) across the whole population. Thus, the total i-score is superior to the current Banff i-score and most diagnostic Banff categories in predicting outcome and assessing the molecular phenotype of renal allografts.

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

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

Kidney transplantation from hepatitis B surface antigen positive donors into hepatitis B surface antibody positive recipients: a prospective nonrandomized controlled study from a single center

The number of patients on renal transplant waiting list is increasing rapidly in many countries, exacerbating the shortage of organs. We conducted a study to evaluate the safety and efficacy of deceased-donor kidney transplantation from hepatitis B surface antigen (HBsAg)-positive (+) donors into hepatitis B surface antibody (anti-HBs)-positive (+) recipients. Sixty-five patients received grafts from HBsAg(+) donors, and 308 subjects received grafts from HBsAg-negative(-) donors. Posttransplantation, recipients with HBsAg(-) grafts or HBsAg(+) grafts received 400 U of hepatitis B immunoglobulin once and twice, respectively. The seven recipients who received grafts from hepatitis B virus (HBV) DNA(+) donors were treated with hepatitis B immunoglobulin 400 U weekly for 3 months and lamivudine 100 mg daily for 6 months. All patients were monitored for liver function and hepatitis B viral status. The follow-up period was 38.7 +/- 15.4 months. Although two recipients developed de novo HBV infection, neither patient developed severe liver dysfunction nor died. The incidence of liver injury (39/65 vs. 207/308, chi-square test, p > 0.05) and survival (log-rank test, p > 0.05) did not differ between the groups. We conclude that anti-HBs(+) recipients receiving HBsAg(+) grafts did as well as those receiving HBsAg(-) grafts.

Subclinical rejection in stable positive crossmatch kidney transplant patients: incidence and correlations

We reviewed 116 surveillance biopsies obtained approximately 1, 3, 6 and 12 months posttransplantation from 50 +XM live donor kidney transplant recipients to determine the frequency of subclinical cell-mediated rejection (CMR) and antibody-mediated rejection (AMR). Subclinical CMR was present in 39.7% of the biopsies at 1 month and >20% at all other time points. The presence of diffuse C4d on biopsies obtained at each time interval ranged from 20 to 30%. In every case, where histological and immunohistological findings were diagnostic for AMR, donor-specific antibody was found in the blood, challenging the long-held belief that low-level antibody could evade detection due to absorption on the graft. Among clinical factors, only recipient age was associated with subclinical CMR. Clinical factors associated with subclinical AMR were recipient age, positive cytotoxic crossmatch prior to desensitization and two mismatches of HLA DR 51, 52 and 53 alleles. Surveillance biopsies during the first year post-transplantation for these high-risk patients uncover clinically occult processes and phenotypes, which without intervention diminish allograft survival and function.

The pathogenesis and treatment of chronic allograft nephropathy

Despite improvements in immunosuppressive therapy, long-term allograft survival after kidney transplantation remains as low as 50%. Chronic allograft nephropathy (CAN) is a major cause of late graft loss in renal transplant recipients. The histopathologic signs of CAN-interstitial fibrosis, tubular atrophy, glomerulopathy and vasculopathy-are nonspecific; therefore, the 2007 Banff classification dispensed with the term CAN in favor of 'interstitial fibrosis and tubular atrophy without evidence of any specific etiology'. In this Review, however, the term CAN is used to describe a clinical syndrome that is characterized by progressive decline in renal function from 3 months after transplantation, accompanied by the development of proteinuria and hypertension. The pathogenesis of CAN is complex and incompletely understood, and involves several immunological and non-immunological factors. We discuss the contributory roles of acute rejection, donor age, anti-human-leukocyte-antigen antibodies, calcineurin inhibitor nephrotoxic effects, viral infection, hypertension and hyperlipidemia. The prevention and treatment of CAN needs multidisciplinary strategies. Early detection by means of protocol biopsy and calculation of glomerular filtration rate is the first step, followed by management of modifiable risk factors.

Pathology: donor biopsy evaluation at time of renal grafting

How can we improve the diagnostic value of donor kidney graft biopsies and the management of renal transplant recipients? A recent study developed a morphologic scoring system -- the Maryland Aggregate Pathology Index -- to help predict long-term renal graft survival from preimplantation donor organ biopsy findings.

Clinicopathologic evaluation of short-term outcome after early corticosteroid discontinuation in kidney transplantation

OBJECTIVES

Steroids have been a gold-standard drug of immunosuppressive regimens in kidney transplantation. Steroid minimization protocols have been applied to minimize the adverse effects of steroids. We have evaluated the short-term outcomes of our early steroid discontinuation regimen.

METHODS

A total of 128 recipients who received kidney from ABO-compatible, flow crossmatch-negative living-related donors were included in this study. Immunosuppressive regimens consisted of tacrolimus (TAC), mycophenolate mofetil (MMF), and basiliximab. In a cohort of recipients, designated as a steroid early discontinuation (ESD) group, only three doses of methylprednisolone (MP) were given (500, 250, 125 mg). In the other cohort of recipients, designated as a chronic steroid (CS) group, MP was given chronically, being tapered to 4 mg at one month post-transplant. TAC and mycophenolic acid (MPA) blood levels were monitored. The following data were retrospectively compared between the two groups at 1, 3, 6, 9, 12 months post-transplant: serum creatinine (sCr), urine protein per gCr (uP/Cr), the incidence of biopsy-proven acute rejection (BPAR), graft survival (GS), area-under-the-curve of blood levels of tacrolimus (TAC-AUC(0-12), ng h/mL) and mycophenolic acid (MPA-AUC(0-12), mug h/mL), MMF dose (mg), the incidence of opportunistic infection, post-transplant diabetes mellitus (PTDM), and histopathologic findings of protocol biopsy according to the Banff '07 classification.

RESULTS

sCr and uP/Cr were comparable between the two groups up to 12 months except for sCr at one month (ESD group > CS group). TAC-AUC(0-12) was significantly higher in ESD group at one month but was equivalent thereafter, while the prevalence of biopsy-proven tubulotoxicity was not different. MMF dose was comparable throughout the period between two groups. The incidence of BPAR until 12 months was equivalent. Of note, 60% of BPAR cases in ESD group occurred within one month. Prevalence of opportunistic infection or PTDM was equivalent. Graft survival was 100% in both groups. The following histopathologic scores up to 12 months were also equivalent: t, i, g, v, ci, ct, cg, cv, mm, ah, and ptc.

CONCLUSIONS

Favorable short-term outcomes were achieved both clinically and histologically using our early steroid discontinuation protocol compared with the conventional protocol with chronic steroid treatment.

[New faces of acute rejection in 2008]

Along the time, the definition of acute rejection has been modified according to the successive Banff classifications, the use of C4d and the identification of anti- HLA antibodies. Both cellular and humoral acute rejection are nowadays considered to be different with regard to definition, pathogenesis and hence treatment. The Banffclassification remains a very useful tool to improve the precision of these definitions. The new technologies such as microarrays should help to identify new aspects of acute rejection.

A case of accelerated acute rejection after ABO-compatible living unrelated kidney transplantation

A 59-yr-old Japanese woman with chronic renal failure caused by IgA nephropathy and antineutrophil cytoplasmic antibody (ANCA)-related glomerulonephritis underwent kidney transplantation from a living unrelated spousal donor. The blood type was compatible, while the human leukocyte antigen (HLA) typing showed a 5/6 locus mismatch. She had become pregnant twice by her donor and had never received blood transfusions. Complement-dependent cytotoxicity cross-match, flow cytometry cross-match (FCXM), and flow panel reactive antibody (PRA) were negative. She initially underwent one week of immunosuppression with mycophenolate mofetil (MMF) and double filtration plasmapheresis (DFPP) immediately before transplantation to reduce the risk of antibody-mediated rejection. Induction therapy consisted of MMF, tacrolimus (TAC), methylprednisolone (MP), and basiliximab. The allograft function was excellent immediately after the operation. However, the urine output and platelet count declined rapidly on post-operative day (POD) 3, while the serum creatinine (sCr) and lactate dehydrogenase levels rose gradually. Subsequently, we could not detect the diastolic arterial flow on Doppler sonography. We diagnosed accelerated acute rejection and treated her with plasma exchange (PEX), intravenous MP pulse therapy, and rituximab. The first episode biopsy on POD 7 revealed acute vascular rejection and acute antibody-mediated rejection (Banff score AMR II). Her urinary excretion increased beginning on POD 13, while the sCr level decreased gradually and reached 0.9 mg/dL on POD 22. In our retrospective analysis, the LAB screen detected donor-specific antibody (DSA). This case suggested that, for successful kidney transplantation in highly sensitized recipients, such as husband-to-wife spousal kidney transplantation with a history of pregnancy, we should keep the risk of AMR in mind, even if the sensitive antibody detection tests are negative.

Biomarkers for early and late stage chronic allograft nephropathy by proteogenomic profiling of peripheral blood

Background

Despite significant improvements in life expectancy of kidney transplant patients due to advances in surgery and immunosuppression, Chronic Allograft Nephropathy (CAN) remains a daunting problem. A complex network of cellular mechanisms in both graft and peripheral immune compartments complicates the non-invasive diagnosis of CAN, which still requires biopsy histology. This is compounded by non-immunological factors contributing to graft injury. There is a pressing need to identify and validate minimally invasive biomarkers for CAN to serve as early predictors of graft loss and as metrics for managing long-term immunosuppression.

Methods

We used DNA microarrays, tandem mass spectroscopy proteomics and bioinformatics to identify genomic and proteomic markers of mild and moderate/severe CAN in peripheral blood of two distinct cohorts (n = 77 total) of kidney transplant patients with biopsy-documented histology.

Findings

Gene expression profiles reveal over 2400 genes for mild CAN, and over 700 for moderate/severe CAN. A consensus analysis reveals 393 (mild) and 63 (moderate/severe) final candidates as CAN markers with predictive accuracy of 80% (mild) and 92% (moderate/severe). Proteomic profiles show over 500 candidates each, for both stages of CAN including 302 proteins unique to mild and 509 unique to moderate/severe CAN.

Conclusions

This study identifies several unique signatures of transcript and protein biomarkers with high predictive accuracies for mild and moderate/severe CAN, the most common cause of late allograft failure. These biomarkers are the necessary first step to a proteogenomic classification of CAN based on peripheral blood profiling and will be the targets of a prospective clinical validation study.

Rituximab and intravenous immunoglobulin treatment of chronic antibody-mediated kidney allograft rejection

Kidney transplant rejections are classified into T-cell-mediated and antibody-mediated rejections (AMR). C4d staining on allograft biopsies and solid-phase assays to measure donor-specific alloantibodies have helped to precisely define the latter. Although for acute AMRs, therapy mainly relies on plasmapheresis or immunoadsorption, no studies for treatment of chronic AMR are available. Here, we report on four kidney allograft recipients suffering from chronic AMR 1 to 27 years posttransplant, who were treated with a combination of rituximab and intravenous immunoglobulin (IVIG). Rituximab/IVIG improved kidney allograft function in all four patients, whereas donor-specific antibodies were reduced in 2 of 4 patients. However, in one patient an acute rejection episode occurred 12 months after this treatment, and another patient had severe, possibly rituximab-associated lung toxicity. Thus, rituximab/IVIG may be a useful strategy for the treatment of chronic AMR, but further randomized multicenter studies are necessary to establish its efficacy and safety profile.

Rabbit antithymocyte globulin is more beneficial in standard kidney than in extended donor recipients

BACKGROUND

In a randomized, international study comparing rabbit antithymocyte globulin (TMG) and basiliximab (BAS) induction in renal transplant recipients at risk for delayed graft function or acute rejection (n=278), TMG was associated with less acute rejection at 1 year.

METHODS

This study analyzed outcomes stratified by standard criteria donor (SCD), extended criteria donor (ECD), and hypertensive donor. Data-capture limitations necessitated defining ECD as donor age more than 60 years or 50 to 60 years with hypertension and renal insufficiency.

RESULTS

Seventy-five recipients received ECD-kidneys (28.4% TMG vs. 25.6% BAS, P=NS) and 203 recipients received SCD-kidneys (72.6% TMG vs. 74.4% BAS, P=NS). Recipients of an ECD or hypertensive donor-kidney had similar outcomes between treatment groups. Recipients of an SCD-kidney treated with TMG had less rejection (odds ratio [OR] 0.48). Recipients of a normotensive donor-kidney treated with TMG had less rejection (OR 0.56). Recipients of a normotensive, SCD-kidney treated with TMG had less rejection (OR 0.47) and death (OR 0.17) than their counterparts treated with BAS.

CONCLUSIONS

Contrary to its perceived niche in recipients of ECD-kidneys, TMG was most beneficial in patients who received a normotensive, deceased SCD kidney.

Direct thrombin inhibitor prevents delayed graft function in a porcine model of renal transplantation

BACKGROUND

Kidney transplantations from donors after cardiac arrest (DCA) are characterized by an increase in the occurrence of delayed graft function and primary nonfunction. In this study, Melagatran, a selective reversible direct thrombin inhibitor was used to limit renal injury in a DCA pig kidney transplantation model.

METHODS

We used a porcine model of DCA to study the effects of treatment with Melagatran in the peri-conservation period. Thromboelastography was used to check Melagatran antithrombin effect on in vitro clot formation. Reverse-transcriptase polymerase chain reaction was used to analyze the peripheral immune cells activation status. Renal function and morphologic study were performed at days 1 and 7. Finally, we analyzed the mechanisms of Melagatran protection on kidney microvasculature primary endothelial cells.

RESULTS

Prolongation of coagulation time (Ex-Tem) was observed 10 min after injection; however, Melagatran did not modulate increases of thrombin-antithrombin complexes following reperfusion. Melagatran significant treatment lowered the proinflammatory status of circulating immune cells. Animal's survival was increased in Melagatran-treated groups (9 of 10 in Melagatran groups vs. 4 of 10 in controls at day 7). Renal injury and inflammation were also significantly reduced in treated groups. We also demonstrated a direct protective effect of Melagatran against endothelial cell activation and inflammation in vitro.

CONCLUSION

Direct thrombin inhibitor administration in the periconservation period improved graft outcome and reduced renal injury in a model of DCA.

Intragraft FOXP3 protein or mRNA during acute renal allograft rejection correlates with inflammation, fibrosis, and poor renal outcome

BACKGROUND

Forkhead box (FOXP3) is considered to be a specific marker for regulatory T cells. The aim of this study was to correlate intragraft FOXP3 at mRNA and cellular levels during renal allograft rejection to response to therapy and late clinical outcome.

METHODS

Immunostainings and quantitative reverse-transcriptase polymerase chain reaction for FOXP3, CD3, and transforming growth factor (TGF)-beta were performed and results were related to histopathologic and clinical outcome.

RESULTS

A good correlation between immunohistochemical analysis and mRNA levels for both CD3 and FOXP3 was observed. Intragraft FOXP3 was significantly related to tubulitis and interstitial fibrosis. A strong correlation was found between FOXP3 and CD3 mRNA and between FOXP3 and TGF-beta mRNA. No correlation was found between FOXP3 and response to therapy.

DISCUSSION

In conclusion, intragraft FOXP3 at both cellular and molecular levels parallels T-cell infiltration during acute rejection. FOXP3 does not predict response to antirejection therapy. FOXP3 correlates with renal fibrosis, TGF-beta, and poor late renal outcome.

Clinical relevance of pretransplant donor-specific HLA antibodies detected by single-antigen flow-beads

BACKGROUND

Defining the clinical relevance of donor-specific HLA-antibodies detected by single-antigen flow-beads (SAFB) is important because these assays are increasingly used for pretransplant risk assessment and organ allocation. The aims of this study were to investigate to which extent HLA-DSA detected by SAFB represent a risk for antibody-mediated rejection (AMR) and diminished allograft survival, and to define HLA-DSA characteristics predictive for AMR.

METHODS

In this retrospective study of 334 patients with negative complement-dependent cytotoxicity crossmatches, day-of-transplant sera were analyzed by SAFB, HLA-DSA determined by virtual crossmatching, and the results correlated with the occurrence of AMR and allograft survival.

RESULTS

Sixty-seven of 334 patients (20%) had HLA-DSA. The incidence of clinical/subclinical AMR at day 200 posttransplant was significantly higher in patients with HLA-DSA than in patients without HLA-DSA (55% vs. 6%; P<0.0001). Notably, 30/67 patients with HLA-DSA (45%) did not experience clinical/subclinical AMR. Death-censored 5-year allograft survival was equal in patient without HLA-DSA and patients with HLA-DSA but no AMR (89% vs. 87%; P=0.95), whereas it was 20% lower in patients with HLA-DSA and AMR (68%; P=0.002). The number, class, and cumulative strength of HLA-DSA determined by SAFB, and prior sensitizing events were not predictive for the occurrence of AMR.

CONCLUSIONS

These results support the utility of SAFB for pretransplant risk assessment and organ allocation, and suggest that improvement of the positive predictive value of HLA-DSA defined by SAFB will require an enhanced definition of pathogenic factors of HLA-DSA.

Case-matched comparison of long-term results of non-heart beating and heart-beating donor renal transplants

BACKGROUND

Function and survival of non-heart-beating donor (NHBD) renal transplants have been shown to be comparable to those from heart-beating donors (HBDs) up to 10 years after transplantation. However, there are few data on outcome after 10 years, particularly from uncontrolled NHBD donors.

METHODS

All NHBD renal transplants (predominantly uncontrolled) performed between April 1992 and January 2002 were retrospectively matched with HBD renal transplants performed over the same period.

RESULTS

Some 112 NHBD renal transplants were compared with 164 HBD renal transplants. Delayed graft function was significantly higher in the NHBD group (83.9 versus 22.0 per cent respectively; P < 0.001). Primary non-function rates were similar (5.4 versus 1.8 per cent respectively; P = 0.164). Overall serum creatinine was significantly higher in NHBDs (P < 0.001). Median graft and patient survival was 126 months for NHBD and 159 months for HBD kidneys. Death-censored graft survival at 1, 5, 10 and 15 years was respectively 91.8, 77.5, 61.0 and 44.2 per cent for NHBD, and 91.1, 86.3, 71.7 and 58.5 per cent for HBD kidneys (P = 0.108).

CONCLUSION

Despite increased delayed graft function rates and serum creatinine levels, the long-term survival of NHBD renal transplants was similar to those from HBDs. However, there was a trend to poorer function and survival from 10 years after transplant.

Emerging role of donor-specific anti-human leukocyte antigen antibody determination for clinical management after solid organ transplantation

Preformed and de novo donor-specific HLA antibodies (DSA) have been associated with allograft dysfunction and failure. The application of solid-phase methods have increased the sensitivity and specificity of antibody detection; however the clinical significance of these DSA is under evaluation. In the present study, we summarize six cases (four renal transplant recipients, one multivisceral recipient, and one heart-and-lung transplant recipient) to illustrate the role of the histocompatibility laboratory in providing the most comprehensive workup to assess the risk of graft dysfunction associated with antibody-mediated rejection (AMR). These cases illustrate the potential risk assessment for AMR in various situations: (1) in patients exhibiting low levels of DSA pretransplantation; (2) protocol immunosuppression minimization during stepwise weaning; and (3) desensitization protocols. Furthermore, increased sensitivity of DSA determination is indicated for the interpretation of focal C4d and its clinical significance. The clinical relevance of monitoring for circulating DSA with solid-phase single-antigen assays is also discussed. These cases exemplify the rationale for all patients to be monitored for DSA post-transplantation, with the frequency adjusted based on the individual risk for AMR.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Urinary CXCL9 and CXCL10 levels correlate with the extent of subclinical tubulitis

Subclinical tubulitis has been associated with the later development of interstitial fibrosis and tubular atrophy (IF/TA), leading to diminished allograft survival. The aim of this study was to investigate how concentrations of urinary CXC-receptor 3 (CXCR3) chemokines (i.e. CXCL4/9/10/11) and CCL2 relate to the extent of subclinical tubulitis. Using ELISA, urinary CXCR3 chemokines, CCL2 and tubular injury markers (i.e. urinary NGAL and alpha1-microglobulin [alpha1 m]) were measured in patients with stable estimated GFR >or=40 mL/min exhibiting normal tubular histology (n = 24), subclinical borderline tubulitis (n = 18) or subclinical tubulitis Ia/Ib (n = 22), as well as in patients with clinical tubulitis Ia/Ib (n = 17) or IF/TA (n = 10). CXCL9 and CXCL10 were significantly higher in subclinical tubulitis Ia/Ib than in subclinical borderline tubulitis (p <or= 0.03) and normal tubular histology (p <or= 0.0002). By contrast, NGAL, alpha1-m, CXCL4, CXCL11 and CCL2 were not or only marginally distinctive across these patient groups. All urinary chemokines and tubular injury markers were higher in clinical tubulitis Ia/Ib than in normal tubular histology (p <or= 0.002), but only tubular injury markers were elevated in IF/TA. These results demonstrate a correlation of urinary CXCL9 and CXCL10 levels with the extent of subclinical tubulitis suggesting potential as noninvasive screening biomarkers.

Recent developments in kidney transplantation--a critical assessment

Rapid advances have been made in decreasing acute rejection rates and improving short-term graft survival in kidney transplant recipients. Whether these advances ultimately will lead to a commensurate improvement in long-term survival is not yet known. In recent years, greater attention has been placed on defining the precise etiology of graft loss, determining how far and with what agents we can minimize immunosuppression, and delineating the nature of both T-cell-mediated as well as antibody-mediated rejection. In addition, with the growing disparity of available organs and patients in need of a transplant, greater attention has been placed on optimizing allocation. In this minireview, we will focus on developments over the last couple of years, paying particular attention to insights, studies and observations that may attempt to elucidate some of these open questions.

Treatment of symptomatic transplant glomerulopathy with rituximab

Kidney transplant glomerulopathy (TG) has a poor outcome as there are no known effective therapies. Therefore, we investigated whether rituximab therapy (RTx) could halt progression of established TG. Fourteen kidney-transplant patients (nine of whom were men), with median age of 54 (range: 30-74) years, of whom seven had biologic markers for HCV infection, underwent a kidney biopsy (KB) at 118 months post-transplant because of impaired allograft function, associated with albuminuria (95-13430 mg/day), within nephrotic-range albuminuria in seven patients. KBs showed no evidence of acute cellular rejection but showed TG. Donor-specific anti-HLA antibodies were present in six cases. When diagnosis of TG was made, patients were placed on rituximab therapy (RTx) (2-4 injections of 375 mg/m2 week), and other concurrent immunosuppression treatments were not modified. By last follow up post-RTx (30 months), seven (50%) patients had lost their kidney within 6-26 months and the other seven had stable creatinine (182 vs. 161 micromol/l; NS), and albuminuria had decreased from 2660 to 500 mg/day (P = 0.03). There was prolonged B-cell lymphopenia (from 71 to 0/mm3) whereas immunoglobulin G, A, M levels remained stable, and four patients (28.5%) experienced severe infectious complications. We conclude that long-term RTx in kidney-transplant patients with TG is associated with allograft function/stabilization in 50% of cases.

Neutrophilic tubulitis as a marker for urinary tract infection in renal allograft biopsies with C4d deposition

BACKGROUND

Neutrophilic tubulitis accompanied by intratubular neutrophil clusters in the renal allograft is a surrogate marker for urinary tract infection (UTI). Overlapping histologic findings can occur in antibody-mediated rejection, which is characterized by peritubular capillary (PTC) deposition of C4d. This study evaluated the incidence of UTI in biopsies with concurrent neutrophilic tubulitis and PTC C4d staining.

METHODS

Thirty-three allograft biopsies from 27 patients selected for the presence of simultaneous C4d staining and neutrophilic tubulitis were correlated with urine culture (U/C) results.

RESULTS

U/C obtained on the same day as the biopsy confirmed UTI in 13 of 33 (39%) biopsies. Among 20 patients with negative U/C; prior culture results within 10 days of the biopsy were available for nine patients, and 5 of 9 (55%) were positive. Thus, UTI was confirmed in 18 of 33 (54%) biopsies. Biopsy interpretation and clinical management was confounded by changes of concurrent acute cellular rejection and antibody-mediated rejection confirmed by demonstration of donor-specific antibodies. Combined therapy with antibiotics and antirejection medications (ART) was administered to 12 of 18 (67%) patients.

CONCLUSIONS

Neutrophilic tubulitis accompanied by neutrophil clusters in the tubular lumen is a useful marker of UTI, even in the presence of PTC C4d deposition. Therapeutic response to antibiotics is limited by co-existent T-cell or antibody-mediated rejection and underlying chronic allograft nephropathy.

Predominant Th1 and cytotoxic phenotype in biopsies from renal transplant recipients with transplant glomerulopathy

Transplant glomerulopathy (TGP) appears to be a pathogenic feature of chronic antibody-mediated rejection, but the pathogenesis of this histologic entity is still poorly understood. Previous studies suggest the involvement of lymphocytes but the phenotypes of these cells have never been analyzed. Here, we report the first study of mRNAs for specific markers of CD4+ T cells including Th1 (T-bet and INFgamma), Th2 (IL4 and GATA3), Treg (Foxp3) and Th17 (IL-17 and RORgammat) subsets, cytotoxic CD8 T cells (Granzyme B) and B-cell markers (CD20) in renal biopsies from renal transplant recipients suffering interstitial fibrosis and tubular atrophy (IF/TA) with or without TGP but with a similar inflammatory score and controls including transplant recipients with normal renal function. Only INFgamma, T-bet (both functionally defined markers of Th1 CD4 T cells) and granzyme B (a CD8 cytotoxic marker) were significantly more strongly expressed in patients with TGP than in patients without TGP and normal controls. These results indicate a role of an active T-mediated inflammatory and cytotoxic process in the pathogenesis of TGP.

Transplant glomerulopathy: clinical and pathological correlations

OBJECTIVE

Chronic transplant glomerulopathy (TG) is one of the leading causes of severe posttransplantation proteinuria and graft loss. Our current knowledge about risk factors for the development of TG, as well as factors that affect its dynamics and prognosis, is poor. We sought to describe the pathological and clinical risk factors and correlations of TG as well as parameters that influenced the survival of grafts with that pathology.

MATERIALS AND METHODS

We retrospectively reevaluated 86 kidney transplant cases with TG that have been recognized on the basis of an indication biopsy since 1997. All TG as well as all pre-TG (previous) biopsies were characterized for the presence of C4d deposits in the graft.

RESULTS

Younger recipient age and minimal immunosuppression due to drug withdrawal or suboptimal drug doses/blood levels within 3 to 6 months preceding the biopsy were associated with C4d deposition in peritubular capillaries (PTC; P = .0053 and P = .0365, respectively). Diffuse PTC-itis (P = .029, RR [95% confidence interval] = 3.349 [1.131-9.919]) and total interstitial inflammation score (P = .015, RR [95% confidence interval] = 9.662 [1.784-52.329]) were observed to show a negative impact on graft survival. C4d deposition in PTC and glomeruli, the level of pretransplantation sensitization, episodes of acute rejection, and C4d in previous (pre-TG) biopsies did not influence the survival of grafts with TG.

CONCLUSIONS

Younger recipient age and minimal immunosuppression were associated with C4d positivity in grafts with TG. The survival of kidney grafts with TG was significantly affected by the magnitude of inflammation in the interstitium and PTC, but not by C4d positivity in PTC and glomeruli.

Non-invasive imaging of acute renal allograft rejection in rats using small animal F-FDG-PET

BACKGROUND

At present, renal grafts are the most common solid organ transplants world-wide. Given the importance of renal transplantation and the limitation of available donor kidneys, detailed analysis of factors that affect transplant survival are important. Despite the introduction of new and effective immunosuppressive drugs, acute cellular graft rejection (AR) is still a major risk for graft survival. Nowadays, AR can only be definitively by renal biopsy. However, biopsies carry a risk of renal transplant injury and loss. Most important, they can not be performed in patients taking anticoagulant drugs.

METHODOLOGY/PRINCIPAL FINDINGS

We present a non-invasive, entirely image-based method to assess AR in an allogeneic rat renal transplantation model using small animal positron emission tomography (PET) and (18)F-fluorodeoxyglucose (FDG). 3 h after i.v. injection of 30 MBq FDG into adult uni-nephrectomized, allogeneically transplanted rats, tissue radioactivity of renal parenchyma was assessed in vivo by a small animal PET-scanner (post operative day (POD) 1,2,4, and 7) and post mortem dissection. The mean radioactivity (cps/mm(3) tissue) as well as the percent injected dose (%ID) was compared between graft and native reference kidney. Results were confirmed by histological and autoradiographic analysis. Healthy rats, rats with acute CSA nephrotoxicity, with acute tubular necrosis, and syngeneically transplanted rats served as controls. FDG-uptake was significantly elevated only in allogeneic grafts from POD 1 on when compared to the native kidney (%ID graft POD 1: 0.54+/-0.06; POD 2: 0.58+/-0.12; POD 4: 0.81+/-0.06; POD 7: 0.77+/-0.1; CTR: 0.22+/-0.01, n = 3-28). Renal FDG-uptake in vivo correlated with the results obtained by micro-autoradiography and the degree of inflammatory infiltrates observed in histology.

CONCLUSIONS/SIGNIFICANCE

We propose that graft FDG-PET imaging is a new option to non-invasively, specifically, early detect, and follow-up acute renal rejection. This method is potentially useful to improve post-transplant rejection monitoring.

Specificity and sensitivity of screening for anti-HLA antibodies in kidney allograft dysfunction

BACKGROUND

Prospective testing for posttransplant circulating anti-HLA antibodies seems to be a critical noninvasive tool, but confirmatory data are lacking.

MATERIALS AND METHODS

Over the last 3 years, peritubular capillary (PTC) C4d deposition was prospectively sought by an immunofluorescence technique applied to frozen tissue in biopsies obtained for allograft dysfunction. Screening for circulating anti-HLA class I/II alloantibodies (AlloAb) by the flow cytometric test was performed simultaneously.

RESULTS

We evaluated 132 sets of biopsies and simultaneous serum samples. PTC C4d deposition was demonstrated in 15.9% (21/132) of biopsies. Circulating anti-HLA I/II AlloAb were detected in 25% (33/132) of serum samples. Employing receiver-operator characteristic (ROC) curves for all C4d-positive biopsies, screening for AlloAb showed a global specificity of 82% and sensitivity of 61.9%. When this analysis was restricted to biopsies obtained in the first month posttransplantation, the sensitivity increased to 81.8%, but the specificity decreased to 76.9%. After the first month posttransplantation, we observed sensitivity of 40.0% and a specificity of 86.4%. In the first month posttransplantation, all patients with a diagnosis of acute antibody-mediated rejection displayed circulating anti-HLA class I/II, but not always at the same time as the C4d-positive biopsy.

CONCLUSIONS

In the first month posttransplantation, prospective monitoring of anti-HLA antibodies may be useful. The high sensitivity allows the identification of patients at risk, affording an earlier diagnosis of antibody-mediated rejection. After the first month, the test can be used to evaluate allograft dysfunction episodes, since positivity is highly suggestive of an antibody-mediated process.

Treatment of Strongyloides stercoralis hyperinfection-associated septic shock and acute respiratory distress syndrome with drotrecogin alfa (activated) in a renal transplant recipient

We report a case of Strongyloides stercoralis hyperinfection syndrome in a renal transplant recipient complicated by septic shock, acute respiratory distress syndrome, and Klebsiella pneumoniae superinfection. The patient was treated successfully with drotrecogin alfa (activated), parenteral ivermectin, albendazole, and piperacillin/tazobactam. This outcome suggests that drotrecogin alfa (activated) may be useful therapy for transplant recipients who develop severe sepsis or septic shock secondary to potentially lethal opportunistic infections.

Focal C4d+ in renal allografts is associated with the presence of donor-specific antibodies and decreased allograft survival

Diffuse peritubular capillary C4d deposition in renal allograft biopsies is associated with donor-specific antibodies (DSA) and graft failure. The significance of focal C4d+ is unclear. We reviewed 368 biopsies from 301 patients performed for renal dysfunction or proteinuria over 5 years. Diffuse C4d+, focal C4d+ and C4d- detected by immunofluorescence occurred in 9.5%, 20.9% and 69.4% of biopsies, respectively. Patients were similar in gender, age, cause of renal disease, donor source, HLA mismatch, serum creatinine at baseline and interval from transplantation to biopsy. Diffuse and focal C4d+ were associated with acute cellular rejection (p < 0.001). Transplant glomerulopathy was associated with diffuse C4d+. DSA at the time of biopsy, were positive in 79.3% of diffusely C4d+ patients, 68.8% of those with focal C4d+ (p = 0.27) and 9.9% of patients with C4d- (p < 0.001, compared to either the focal or diffuse groups, respectively). Allograft survival at 40 months was lower in diffuse C4d+ compared to the C4d- group (p = 0.014), but not when compared to the focal C4d+ group. There was a clear trend toward worse graft survival in patients with focal C4d+ in this time interval, but focal C4d+ compared to both diffuse C4d+ and C4d-groups was not statistically significant (p = 0.08).

Indirect CD4+ TH1 response, antidonor antibodies and diffuse C4d graft deposits in long-term recipients conditioned by donor antigens priming

Priming of recipients by DST induces long-term survival of mismatched allografts in adult rats. Despite these recipients developing inducible T regulatory cells able to transfer long-term graft survival to a secondary host, a state of chronic rejection is also observed. We revisited the molecular donor MHC targets of the cellular response in acute rejection and analyzed the cellular and humoral responses in recipients with long-term graft survival following transplantation. We found three immunodominant peptides, all derived from LEW.1W RT1.D(u) molecules to be involved in acute rejection of grafts from unmodified LEW.1A recipients. Although the direct pathway of allorecognition was reduced in DST-treated recipients, the early CD4+ indirect pathway response to dominant peptides was almost unimpaired. We also detected early and sustained antidonor class I and II antibody subtypes with diffuse C4d deposits on graft vessels. Finally, long-term accepted grafts displayed leukocyte infiltration, endarteritis and fibrosis, which evolved toward vascular narrowing at day 100. Altogether, these data suggest that the chronic graft lesions developed in long-term graft recipients are the result of progressive humoral injury associated with a persisting indirect T helper response. These features may represent a useful model for understanding and manipulating chronic active antibody-mediated rejection in human.

MicroRNA expression profiles predictive of human renal allograft status

Immune rejection of organ transplants is a life-threatening complication and is exemplified by alterations in the expression of protein-encoding genes. Because microRNAs (miRNAs) regulate the expression of genes implicated in adaptive immunity, we investigated whether acute rejection (AR) is associated with alterations in miRNA expression within allografts and whether expression profiles are diagnostic of AR and predict allograft function. Seven of 33 renal allograft biopsies (12 AR and 21 normal) were profiled using microfluidic cards containing 365 mature human miRNAs (training set), and a subset of differentially expressed miRNAs were quantified in the remaining 26 allograft biopsies (validation set). We found a strong association between intragraft expression of miRNAs and messenger RNAs (mRNAs), and that AR, and renal allograft function, could be predicted with a high level of precision using intragraft levels of miRNAs. Our investigation of miRNA expression in normal human peripheral blood mononuclear cells (PBMCs) showed that miRNAs (miR-142-5p, -155, and -223) overexpressed in AR biopsies are highly expressed in PBMCs, and that stimulation with the mitogen phytohaemagglutinin results in an increase in the abundance of miR-155 and a decrease in miR-223 and let-7c. Quantification of miRNAs in primary cultures of human renal epithelial cells (HRECs) showed that miR-30a-3p, -10b, and let-7c are highly expressed in HRECs, and that stimulation results in a decreased expression of miR-30a-3p. Our studies, in addition to suggesting a cellular basis for the altered intragraft expression of miRNAs, propose that miRNA expression patterns may serve as biomarkers of human renal allograft status.