Acute Rejection Phenotypes in the Current Era of Immunosuppression: A Single-Center Analysis

Randomized Trial to Assess the Clinical Utility of Renal Allograft Monitoring by Urine CXCL10 Chemokine

SIGNIFICANCE STATEMENT

This study is the first randomized controlled trial to investigate the clinical utility of a noninvasive monitoring biomarker in renal transplantation. Although urine CXCL10 monitoring could not demonstrate a beneficial effect on 1-year outcomes, the study is a rich source for future design of trials aiming to explore the clinical utility of noninvasive biomarkers. In addition, the study supports the use of urine CXCL10 to assess the inflammatory status of the renal allograft.

BACKGROUND

Urine CXCL10 is a promising noninvasive biomarker for detection of renal allograft rejection. The aim of this study was to investigate the clinical utility of renal allograft monitoring by urine CXCL10 in a randomized trial.

METHODS

We stratified 241 patients, 120 into an intervention and 121 into a control arm. In both arms, urine CXCL10 levels were monitored at three specific time points (1, 3, and 6 months post-transplant). In the intervention arm, elevated values triggered performance of an allograft biopsy with therapeutic adaptations according to the result. In the control arm, urine CXCL10 was measured, but the results concealed. The primary outcome was a combined end point at 1-year post-transplant (death-censored graft loss, clinical rejection between month 1 and 1-year, acute rejection in 1-year surveillance biopsy, chronic active T-cell-mediated rejection in 1-year surveillance biopsy, development of de novo donor-specific HLA antibodies, or eGFR <25 ml/min).

RESULTS

The incidence of the primary outcome was not different between the intervention and the control arm (51% versus 49%; relative risk (RR), 1.04 [95% confidence interval, 0.81 to 1.34]; P = 0.80). When including 175 of 241 (73%) patients in a per-protocol analysis, the incidence of the primary outcome was also not different (55% versus 49%; RR, 1.11 [95% confidence interval, 0.84 to 1.47]; P = 0.54). The incidence of the individual end points was not different as well.

CONCLUSIONS

This study could not demonstrate a beneficial effect of urine CXCL10 monitoring on 1-year outcomes (ClinicalTrials.gov_ NCT03140514 ).

Biomarker-Development Proteomics in Kidney Transplantation: An Updated Review

Kidney transplantation (KT) is the optimal therapeutic strategy for patients with end-stage renal disease. The key to post-transplantation management is careful surveillance of allograft function. Kidney injury may occur from several different causes that require different patient management approaches. However, routine clinical monitoring has several limitations and detects alterations only at a later stage of graft damage. Accurate new noninvasive biomarker molecules are clearly needed for continuous monitoring after KT in the hope that early diagnosis of allograft dysfunction will lead to an improvement in the clinical outcome. The advent of “omics sciences”, and in particular of proteomic technologies, has revolutionized medical research. Proteomic technologies allow us to achieve the identification, quantification, and functional characterization of proteins/peptides in biological samples such as urine or blood through supervised or targeted analysis. Many studies have investigated proteomic techniques as potential molecular markers discriminating among or predicting allograft outcomes. Proteomic studies in KT have explored the whole transplant process: donor, organ procurement, preservation, and posttransplant surgery. The current article reviews the most recent findings on proteomic studies in the setting of renal transplantation in order to better understand the effective potential of this new diagnostic approach.

Seeking Standardized Definitions for HLA-incompatible Kidney Transplants: A Systematic Review

BACKGROUND

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

Proposed Definitions of Antibody-Mediated Rejection for Use as a Clinical Trial Endpoint in Kidney Transplantation

Antibody-mediated rejection (AMR) is caused by antibodies that recognize donor human leukocyte antigen (HLA) or other targets. As knowledge of AMR pathophysiology has increased, a combination of factors is necessary to confirm the diagnosis and phenotype. However, frequent modifications to the AMR definition have made it difficult to compare data and evaluate associations between AMR and graft outcome. The present paper was developed following a Broad Scientific Advice request from the European Society for Organ Transplantation (ESOT) to the European Medicines Agency (EMA), which explored whether updating guidelines on clinical trial endpoints would encourage innovations in kidney transplantation research. ESOT considers that an AMR diagnosis must be based on a combination of histopathological factors and presence of donor-specific HLA antibodies in the recipient. Evidence for associations between individual features of AMR and impaired graft outcome is noted for microvascular inflammation scores ≥2 and glomerular basement membrane splitting of >10% of the entire tuft in the most severely affected glomerulus. Together, these should form the basis for AMR-related endpoints in clinical trials of kidney transplantation, although modifications and restrictions to the Banff diagnostic definition of AMR are proposed for this purpose. The EMA provided recommendations based on this Broad Scientific Advice request in December 2020; further discussion, and consensus on the restricted definition of the AMR endpoint, is required.

Outcome of Husband-to-Wife Kidney Transplantation With Mutual Children: Single Center Experience Using T Cell-Depleting Induction and Review of the Literature

Few data on husband-to-wife transplantations with mutual children (H2W) exist in the current era. We investigated the outcome of H2W transplantations (n = 25) treated with T cell-depleting induction compared to women with prior pregnancies also receiving their first HLA-mismatched kidney transplant, but from a different donor source: (i) other living donor (n = 52) and (ii) deceased donor (n = 120). Seventy-four percent of the women had ≥2 pregnancies; median follow-up time was 5 years. Death-censored allograft survival was significantly lower in the H2W group compared to the other two groups (p = 0.03). Three of four graft losses in the H2W group were due to rejection. 5-year patient survival in the H2W group was high and similar compared to the other living donor group (100 vs. 98%; p = 0.28). The incidence of (sub)clinical antibody-mediated rejection was higher in the H2W group (36 vs. 20 vs. 18%) (p = 0.10). The frequency of infections was similar among the three groups. No immunological parameter was predictive for rejection or graft loss in H2W transplantations. In conclusion, H2W transplantation is a valuable option, but associated with a higher risk for allograft loss due to rejection despite T cell-depleting induction. Further research is required for better risk prediction on an individual patient level.

Short- and long-term impact of neutropenia within the first year after kidney transplantation

The aim of this retrospective single-center study was to investigate short- and long-term impact of neutropenia occurring within the first year after kidney transplantation, with a special emphasis on different neutropenia grades. In this unselected cohort, 225/721 patients (31%) developed 357 neutropenic episodes within the first year post-transplant. Based on the nadir neutrophil count, patients were grouped as neutropenia grade 2 (<1.5-1.0*10⁹ /L; n=105), grade 3 (<1.0-0.5*10⁹ /L; n=65), and grade 4 (<0.5*10⁹ /L; n=55). Most neutropenia episodes were presumably drug-related (71%) and managed by reduction/discontinuation of potentially responsible drugs (mycophenolic acid [MPA] 51%, valganciclovir 25%, trimethoprim/sulfamethoxazole 19%). Steroids were added/increased as replacement for reduced/discontinued MPA. Granulocyte colony-stimulating factor was only used in 2/357 neutropenia episodes (0.6%). One-year incidence of (sub)clinical rejection, one-year mortality as well as long-term patient and graft survival were not different among patient without neutropenia and neutropenia grade 2/3/4. However, the incidence of infections was about 3-times higher during neutropenia grade 3 and 4, but not increased during grade 2. In conclusion, neutropenia within the first year after kidney transplantation represents no increased risk for rejection and has no negative impact on long-term patient and graft survival. Adding/increasing steroids as replacement for reduced/discontinued MPA might supplement management of neutropenia.

Clinical Relevance of Corticosteroid Withdrawal on Graft Histological Lesions in Low-Immunological-Risk Kidney Transplant Patients

The impact of corticosteroid withdrawal on medium-term graft histological changes in kidney transplant (KT) recipients under standard immunosuppression is uncertain. As part of an open-label, multicenter, prospective, phase IV, 24-month clinical trial (ClinicalTrials.gov, NCT02284464) in low-immunological-risk KT recipients, 105 patients were randomized, after a protocol-biopsy at 3 months, to corticosteroid continuation (CSC, n = 52) or corticosteroid withdrawal (CSW, n = 53). Both groups received tacrolimus and MMF and had another protocol-biopsy at 24 months. The acute rejection rate, including subclinical inflammation (SCI), was comparable between groups (21.2 vs. 24.5%). No patients developed dnDSA. Inflammatory and chronicity scores increased from 3 to 24 months in patients with, at baseline, no inflammation (NI) or SCI, regardless of treatment. CSW patients with SCI at 3 months had a significantly increased chronicity score at 24 months. HbA1c levels were lower in CSW patients (6.4 ± 1.2 vs. 5.7 ± 0.6%; p = 0.013) at 24 months, as was systolic blood pressure (134.2 ± 14.9 vs. 125.7 ± 15.3 mmHg; p = 0.016). Allograft function was comparable between groups and no patients died or lost their graft. An increase in chronicity scores at 2-years post-transplantation was observed in low-immunological-risk KT recipients with initial NI or SCI, but CSW may accelerate chronicity changes, especially in patients with early SCI. This strategy did, however, improve the cardiovascular profiles of patients.

Impact of HLA Mismatching on Early Subclinical Inflammation in Low-Immunological-Risk Kidney Transplant Recipients

The impact of human leukocyte antigen (HLA)-mismatching on the early appearance of subclinical inflammation (SCI) in low-immunological-risk kidney transplant (KT) recipients is undetermined. We aimed to assess whether HLA-mismatching (A-B-C-DR-DQ) is a risk factor for early SCI. As part of a clinical trial (Clinicaltrials.gov, number NCT02284464), a total of 105 low-immunological-risk KT patients underwent a protocol biopsy on the third month post-KT. As a result, 54 presented SCI, showing a greater number of total HLA-mismatches (p = 0.008) and worse allograft function compared with the no inflammation group (48.5 ± 13.6 vs. 60 ± 23.4 mL/min; p = 0.003). Multiple logistic regression showed that the only risk factor associated with SCI was the total HLA-mismatch score (OR 1.32, 95%CI 1.06-1.64, p = 0.013) or class II HLA mismatching (OR 1.51; 95%CI 1.04-2.19, p = 0.032) after adjusting for confounder variables (recipient age, delayed graft function, transfusion prior KT, and tacrolimus levels). The ROC curve illustrated that the HLA mismatching of six antigens was the optimal value in terms of sensitivity and specificity for predicting the SCI. Finally, a significantly higher proportion of SCI was seen in patients with >6 vs. ≤6 HLA-mismatches (62.3 vs. 37.7%; p = 0.008). HLA compatibility is an independent risk factor associated with early SCI. Thus, transplant physicians should perhaps be more aware of HLA mismatching to reduce these early harmful lesions.

Screening strategy for de novo donor-specific HLA antibodies beyond the first year after kidney transplantation: Personalized or "one size fits all"?

Screening for de novo donor-specific HLA antibodies (DSAs) after kidney transplantation is widely recommended. The aim of this single-center, cross-sectional study was to investigate the frequency of therapeutic interventions triggered by de novo DSA screening. We included 464 patients screened for de novo DSA at annual visits after a median of 5 years post-transplant (range 1 to 19 years). Overall, de novo DSAs were detected in 55/464 patients (11.9%) with a stepwise increase of the prevalence from 4.9% at 1 year post-transplant to 18.9% at >10 years post-transplant. Subsequent allograft biopsies were performed in 24/55 patients (44%). The main reasons to omit biopsies were good/stable allograft function and anticipated lack of clinical consequences (eg, relevant comorbidities). Rejection processes were detected in 16/24 biopsies (67%). Therapeutic interventions were made in 18/464 screened patients (3.9%) with a significantly higher rate in the youngest quartile of patients (≤48 years; 7.9%) compared to the middle 50% (49-67 years; 3%) and the oldest quartile (≥68 years; 1.7%) (P = .03). Our study suggests that the frequency of therapeutic interventions triggered by de novo DSA screening after kidney transplantation is overall low, but significantly higher in younger patients, arguing for a personalized, age-adapted de novo DSA screening strategy.

Revisiting cytomegalovirus serostatus and replication as risk factors for inferior long-term outcomes in the current era of renal transplantation

BACKGROUND

Cytomegalovirus (CMV) serostatus and CMV replication are considered as risk factors for inferior graft and patient survival after renal transplantation, but long-term outcome data are limited. The aim of this retrospective single-centre study was to investigate the impact of CMV serostatus and CMV replication/disease on long-term outcomes in a well-defined cohort managed by a standardized CMV prevention/treatment protocol.

METHODS

We investigated 599 consecutive kidney transplantations having a CMV prevention protocol consisting of either prophylaxis (D+/R- and R+ with ATG induction) or screening/deferred therapy (R+ without ATG induction). Patients were grouped according to CMV serostatus [high risk (D+/R-): n = 122; intermediate risk (R+): n = 306; low risk (D-/R-): n = 171] and occurrence of CMV replication/disease (no CMV replication: n = 419; asymptomatic CMV replication: n = 110; CMV syndrome: n = 39; tissue-invasive CMV disease: n = 31). The median follow-up time was 6.5 years.

RESULTS

Graft and patient survival were not different among the three CMV serostatus groups as well as the four CMV replication/disease groups (P ≥ 0.44). Eighty-seven patients died, 17 due to infections (21%), but none was attributable to CMV. The overall hospitalization incidence for CMV-related infection was 3% (17/599 patients). The incidence of clinical and (sub)clinical rejection was similar among the groups (P ≥ 0.17). In a multivariate Cox proportional hazard model, neither CMV serostatus, nor CMV replication, nor CMV disease were independent predictors for patient death or graft failure, respectively.

CONCLUSIONS

This retrospective single-centre study suggests that the negative impact of CMV infection on long-term patient and allograft survival as well as on allograft rejection can be largely eliminated with current diagnostic/therapeutic management.

Precision transplant pathology

PURPOSE OF REVIEW

Transplant pathology contributes substantially to personalized treatment of organ allograft recipients. Rapidly advancing next-generation human leukocyte antigen (HLA) sequencing and pathology are enhancing the abilities to improve donor/recipient matching and allograft monitoring.

RECENT FINDINGS

The present review summarizes the workflow of a prototypical patient through a pathology practice, highlighting histocompatibility assessment and pathologic review of tissues as areas that are evolving to incorporate next-generation technologies while emphasizing critical needs of the field.

SUMMARY

Successful organ transplantation starts with the most precise pratical donor-recipient histocompatibility matching. Next-generation sequencing provides the highest resolution donor-recipient matching and enables eplet mismatch scores and more precise monitoring of donor-specific antibodies (DSAs) that may arise after transplant. Multiplex labeling combined with hand-crafted machine learning is transforming traditional histopathology. The combination of traditional blood/body fluid laboratory tests, eplet and DSA analysis, traditional and next-generation histopathology, and -omics-based platforms enables risk stratification and identification of early subclinical molecular-based changes that precede a decline in allograft function. Needs include software integration of data derived from diverse platforms that can render the most accurate assessment of allograft health and needs for immunosuppression adjustments.

Differential Impact of Delayed Graft Function in Deceased Donor Renal Transplant Recipients With and Without Donor-specific HLA-antibodies

BACKGROUND

Delayed graft function (DGF) and pretransplant donor-specific HLA-antibodies (DSA) are both regarded as risk factors for rejection and lower graft survival. However, the combined impact of DGF and DSA has not been studied in detail.

METHODS

We investigated 375 deceased donor kidney transplantations, which had DSA assignment by single-antigen bead technology and which had surveillance biopsies at 3 of 6 months. Median follow-up time was 6.1 years.

RESULTS

DGF occurred in 137 of 375 patients (37%), and DSA were present in 85 of 375 patients (23%). The incidence of DGF was similar in DSA-positive (DSApos)-patients and DSA-negative (DSAneg)-patients (40% versus 36%; P = 0.45). In DSAneg-patients, 5-year graft survival was not different with/without DGF (81% versus 83%; P = 0.48). By contrast, in DSApos-patients, 5-year graft survival was significantly lower with DGF (64% versus 79%; P = 0.01). Moreover, DSApos-patients with DGF had a higher 1-year incidence of subclinical rejection, which were mostly antibody-mediated or mixed rejection phenotypes. Graft loss due to rejection was significantly more frequent in DSApos-patients with DGF (5/34; 15%) compared to DSApos-patients without DGF (2/51; 4%), and DSAneg-patients with/without DGF (3/103; 3% and 4/187; 2%, respectively) (P = 0.005). In a multivariate Cox model, DSA with DGF was an independent predictor for graft (hazard ratio = 2.84 [95% confidence interval, 1.54-5.06]; P = 0.001) and death-censored graft loss (hazard ratio = 4.65 [95% confidence interval, 1.83-11.51]; P = 0.002).

CONCLUSIONS

DGF has a much more detrimental impact in DSApos-patients than in DSAneg-patients, which is likely related to a higher incidence of antibody-mediated rejection. If possible, the combined risks of DGF and DSA should be avoided.

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.

Reducing calcineurin inhibitor first for treating BK polyomavirus replication after kidney transplantation: long-term outcomes

BACKGROUND

Reducing immunosuppression is the mainstay of treating BK polyomavirus (BKPyV) viraemia after kidney transplantation, but the best approach, efficacy and impact are undefined. We established a standard operating procedure (SOP) treating BKPyV viraemia based on first reducing calcineurin inhibitor ('CNI first'). The aim of this study was to investigate long-term outcomes in 644 consecutive transplantations using this SOP.

METHODS

Patients were monitored for active BKPyV infection by urinary decoy cells and, if positive, by BKPyV viraemia. In case of sustained BKPyV viraemia >1000 copies/mL, immunosuppression was reduced stepwise according to the SOP. Patients were classified as 'no decoy cells' [n = 432 (66%)], 'decoy cells/no viraemia' [n = 107 (17%)] and 'viraemia' [n = 105 (17%)].

RESULTS

At 6-years post-transplant, graft survival was ∼84%, the clinical rejection rate was ∼25% and they were not different among the three groups (P = 0.14; P = 0.91). The median estimated glomerular filtration rate at the last follow-up was similar (range 49-53 mL/min, P = 0.08). Of 105 viraemic patients, 101 (96%) cleared BKPyV viraemia. In 39% of patients, viraemia clearance followed a tacrolimus reduction. A reduction of mycophenolic acid was required in 43% and discontinuation in 3%. No short-term graft loss was directly attributable to BKPyV-associated nephropathy. After a median follow-up of 5 years after clearance of BKPyV viraemia, 11/101 patients (11%) developed clinical rejection: 7 (7%) T-cell-mediated rejection and 4 (4%) antibody-mediated rejection (ABMR).

CONCLUSIONS

Immunosuppression reduction based on 'CNI first' leads to similar long-term outcomes in patients with/without BKPyV viraemia and is associated with a low risk for ABMR after clearance of BKPyV viraemia. Randomized trials are needed to compare the risks and benefits of immunosuppression reduction strategies in kidney transplant patients with BKPyV viraemia.

Non-invasive Biomarkers of Acute Rejection in Kidney Transplantation: Novel Targets and Strategies

Kidney transplantation is considered the favored treatment for patients suffering from end-stage renal disease, since successful transplantation is associated with longer survival and improved quality of life compared to dialysis. Alloreactive immune responses against the donor kidney may lead to acute rejection of the transplant. The current diagnosis of renal allograft rejection mainly relies on clinical monitoring, including serum creatinine, proteinuria, and confirmation by histopathologic assessment in the kidney transplant biopsy. These parameters have their limitations. Identification and validation of biomarkers, which correlate with or predict the presence of acute rejection, and which could improve therapeutic decision making, are priorities for the transplantation community. There is a need for alternative, less invasive but sensitive markers to diagnose acute graft rejection. Here, we provide an overview of the current status on research of biomarkers of acute kidney transplant rejection in blood and urine. We specifically discuss relatively novel research strategies in biomarker research, including transcriptomics and proteomics, and elaborate on donor-derived cell-free DNA as a potential biomarker.

The Spectrum of Histopathological Changes in the Renal Allograft - a 12 Months Protocol Biopsy Study

INTRODUCTION

Renal transplantation became a routine and successful medical treatment for Chronic Kidney Disease in the last 30 years all over the world. Introduction of Luminex based Single Antigen Beads (SAB) and recent BANFF consensus of histopathological phenotypes of different forms of rejection enables more precise diagnosis and changes the therapeutic approach. The graft biopsies, protocol or cause, indicated, remain a golden diagnostic tool for clinical follow up of kidney transplant recipients (KTR).

AIM

The study aimed to analyse the histopathological changes in renal grafts 12 months after the surgery in KTR with satisfactory kidney function.

MATERIAL AND METHODS

A 12-month protocol biopsy study was performed in a cohort of 50 Kidney transplant recipients (42 from living and 8 from deceased donors). Usual work-up for suitable donors and recipients, standard surgical procedure, basic principles of peri and postoperative care and follow up were done in all KTR. Sequential quadruple immunosuppression including induction with Anti-thymocyte globulin (ATG) or Interleukin-2R antagonist (IL-2R), and triple drug maintenance therapy with Calcineurin Inhibitors (CNI), Mycophenolate Mofetil (MMF) and Steroids were prescribed to all pts. Different forms of Glomerulonephritis (16), Hypertension (10), End Stage Renal Disease (13), Hereditary Nephropathies (6), Diabetes (3) and Vesicoureteral Reflux (2) were the underlying diseases. All biopsies were performed under ultrasound guidance. The 16 gauge needles with automated "gun" were used to take 2 cores of tissue. The samples were stained with HE, PAS, Trichrome Masson and Silver and reviewed by the same pathologist. A revised and uploaded BANFF 2013 classification in 6 categories (Cat) was used.

RESULTS

Out of 48 biopsies, 15 (31%) were considered as normal, 4 (8%), Borderline (BL-Cat 3), 5 (10%) as Interstitial Fibrosis/Tubular Atrophy (IF/TA-Cat 5), 5 (10%) were classified as non-immunological (Cat 6), 2 as a pure antibody-mediated rejection (ABMR-Cat 2) and T-cell Mediated Rejection (TCMR-Cat 4). The remaining 17 samples were classified as a "mixed" rejection: 7 (41%) ABMR + IF/TA, 5 (29%) ABMR + BL + IF/TA, 2 (11%) BL + IF/TA, 1 (5%) ABMR + BL, 1 (5%) ABMR + TCMR and 1 (5%) TCMR + IF/TA. The mean serum creatinine at the time of the biopsy was 126.7 ± 23.4 µmol/L, while GFR-MDRD 63.4 ± 20.7 ml/min, which means that the majority of the findings were subclinical. Among the non-immunological histological findings (Cat 6), 3 cases belonged to CNI toxicity, 1 to BK nephropathy and 1 to recurrence of the primary disease.

CONCLUSION

Our 12-month protocol biopsy study revealed the presence of different forms of mixed subclinical rejection. Use of recent BANFF classification and scoring system enables more precise diagnosis and subsequently different approach to the further treatment of the KTR. More correlative long-term studies including Anti HLA antibodies and Endothelial Cell Activation- Associated Transcripts (ENDAT) are needed.