Urine biomarkers informative of human kidney allograft rejection and tolerance

Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices

INTRODUCTION

The successes in the field of pediatric kidney transplantation over the past 60 years have been extraordinary. Year over year, there have been significant improvements in short-term graft survival. However, improvements in longer-term outcomes have been much less apparent. One important contributor has been the phenomenon of low-level rejection in the absence of clinical manifestations-so-called subclinical rejection (SCR).

METHODS

Traditionally, rejection has been diagnosed by changes in clinical parameters, including but not limited to serum creatinine and proteinuria. This review examines the shortcomings of this approach, the effects of SCR on kidney allograft outcome, the benefits and drawbacks of surveillance biopsies to identify SCR, and new urine and blood biomarkers that define the presence or absence of SCR.

RESULTS

Serum creatinine is an unreliable index of SCR. Surveillance biopsies are the method most utilized to detect SCR. However, these have significant drawbacks. New biomarkers show promise. These biomarkers include blood gene expression profiles and donor derived-cell free DNA; urine gene expression profiles; urinary cytokines, chemokines, and metabolomics; and other promising blood and urine tests.

CONCLUSION

Specific emphasis is placed on studies carried out in pediatric kidney transplant recipients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03719339.

Biomarkers in Kidney Transplantation: A Rapidly Evolving Landscape

The last decade has seen an explosion in clinical research focusing on the use of noninvasive biomarkers in kidney transplantation. Much of the published literature focuses on donor-derived cell-free DNA (dd-cfDNA). Although initially studied as a noninvasive means of identifying acute rejection, it is now clear that dd-cfDNA is more appropriately described as a marker of severe injury and irrespective of the etiology, elevated dd-cfDNA ≥0.5% portends worse graft outcomes. Blood gene expression profiling is also commercially available and has mostly been studied in the context of early identification of subclinical rejection, although additional data is needed to validate these findings. Torque teno virus, a ubiquitous DNA virus, has emerged as a biomarker of immunosuppression exposure as peripheral blood Torque teno virus copy numbers might mirror the intensity of host immunosuppression. Urinary chemokine tests including C-X-C motif chemokine ligand 9 and C-X-C motif chemokine ligand 10 have recently been assessed in large clinical trials and hold promising potential for early diagnosis of both subclinical and acute rejection, as well as, for long-term prognosis. Urinary cellular messenger RNA and exosome vesicular RNA based studies require additional validation. Although current data does not lend itself to conclusion, future studies on multimodality testing may reveal the utility of serial surveillance for individualization of immunosuppression and identify windows of opportunity to intervene early and before the irreversible allograft injury sets in.

Unveiling systemic responses in kidney transplantation: interplay between the allograft transcriptome and serum proteins

Immunity, as defined by systems biology, encompasses a holistic response throughout the body, characterized by intricate connections with various tissues and compartments. However, this concept has been rarely explored in kidney transplantation. In this proof-of-concept study, we investigated a direct association between the allograft phenotype and serum protein signatures. Time-matched samples of graft biopsies and blood serum were collected in a heterogeneous cohort of kidney-transplanted patients (n = 15) for bulk RNA sequencing and proteomics, respectively. RNA transcripts exhibit distinct and reproducible, coregulated gene networks with specific functional profiles. We measured 159 serum proteins and investigated correlations with gene expression networks. Two opposing axes-one related to metabolism and the other to inflammation-were identified. They may represent a biological continuum between the allograft and the serum and correlate with allograft function, but not with interstitial fibrosis or proteinuria. For signature validation, we used two independent proteomic data sets (n = 21). Our findings establish a biological link between the allograft transcriptome and the blood serum proteome, highlighting systemic immune effects in kidney transplantation and offering a promising framework for developing allograft-linked biomarkers.

Immune monitoring of allograft status in kidney transplant recipients

Kidney transplant patients require careful management of immunosuppression to avoid rejection while minimizing the risk of infection and malignancy for the best long-term outcome. The gold standard for monitoring allograft status and immunosuppression adequacy is a kidney biopsy, but this is invasive and costly. Conventional methods of allograft monitoring, such as serum creatinine level, are non-specific. Although they alert physicians to the need to evaluate graft dysfunction, by the time there is a clinical abnormality, allograft damage may have already occurred. The development of novel and non-invasive methods of evaluating allograft status are important to improving graft outcomes. This review summarizes the available conventional and novel methods for monitoring allograft status after kidney transplant. Novel and less invasive methods include gene expression, cell-free DNA, urinary biomarkers, and the use of artificial intelligence. The optimal method to manage patients after kidney transplant is still being investigated. The development of less invasive methods to assess allograft function has the potential to improve patient outcomes and allow for a more personalized approach to immunosuppression management.

Evaluation of Immunocompetence and Biomarkers of Tolerance in Chimeric and Immunosuppression-free Kidney Allograft Recipients

BACKGROUND

Thirty-seven patients have received a living-donor kidney transplant in a phase 2 study designed to induce tolerance with facilitated allogeneic hematopoietic stem cell transplant. The study protocol is based on tolerogenic CD8 + /T-cell receptor - facilitating cells (FCR001; also including hematopoietic stem cells and αβ-T-cell receptor + T cells) and low-dose, nonmyeloablative conditioning. Persistent chimerism allowing full immunosuppression (IS) withdrawal was achieved in 26 patients (time off IS 36-123 mo).

METHODS

We evaluated biomarkers of tolerance through urinary cell mRNA profiling and immunocompetence to respond to vaccination in these patients. We also assessed kidney function and metabolic parameters compared with standard-of-care patients on IS.

RESULTS

Persistently chimeric patients retained chimerism after removal of IS and remained rejection free without donor HLA-specific antibody development. The presence of donor chimerism at >50% correlated with a signature of tolerance in urinary cell mRNA profiles, with a uniquely elevated increase in the ratio of cytotoxic T lymphocyte-associated protein 4 to granzyme B mRNA. Tolerance was associated with protection from recurrence of immune-mediated causes of kidney disease. Tolerant participants were safely vaccinated, developed protective immune responses, and did not lose chimerism after vaccination. When compared with kidney transplant recipients treated with standard IS, tolerant participants showed stable kidney function and reduced medication use for hypertension and hyperlipidemia.

CONCLUSIONS

These results suggest that elimination of IS has distinct advantages in living-donor kidney allograft recipients.

Selective modulation of gene expression in activated normal human peripheral blood mononuclear cells by store-operated calcium entry blocker BTP2

Calcium is a critical signaling molecule in many cell types including immune cells. The calcium-release activated calcium channels (CRAC) responsible for store-operated calcium entry (SOCE) in immune cells are gated by STIM family members functioning as sensors of Ca2+ store content in the endoplasmic reticulum. We investigated the effect of SOCE blocker BTP2 on human peripheral blood mononuclear cells (PBMC) stimulated with the mitogen phytohemagglutinin (PHA). We performed RNA sequencing (RNA-seq) to query gene expression at the whole transcriptome level and identified genes differentially expressed between PBMC activated with PHA and PBMC activated with PHA in the presence of BTP2. Among the differentially expressed genes, we prioritized genes encoding immunoregulatory proteins for validation using preamplification enhanced real time quantitative PCR assays. We performed multiparameter flow cytometry and validated by single cell analysis that BTP2 inhibits cell surface expression CD25 at the protein level. BTP2 reduced significantly PHA-induced increase in the abundance of mRNAs encoding proinflammatory proteins. Surprisingly, BTP2 did not reduce significantly PHA-induced increase in the abundance of mRNAs encoding anti-inflammatory proteins. Collectively, the molecular signature elicited by BTP2 in activated normal human PBMC appears to be tipped towards tolerance and away from inflammation.

Urinary dipeptidyl peptidase-4 is a useful marker for tubulitis, and it is released from the tubular cells of kidney transplant recipients

Background

Biomarkers are needed to diagnose kidney rejection in transplant recipients. We evaluated whether dipeptidyl peptidase-4 (DPP-4) could serve as a biomarker of rejection.

Methods

We determined DPP-4 concentrations and enzymatic activities in serum and urine, as well as DPP-4 expression in 49 kidney biopsy samples from 28 kidney transplant recipients. This study was approved by the ethical standards of the institutional research committee and comply with Helsinki declaration. All patients provided their informed consent. Donors were not from prisoners and were not paid or coerced.

Results

Serum and urinary DPP-4 activities closely correlated with DPP-4 concentrations, but were suppressed by DPP-4 inhibitors. Urinary DPP-4 concentrations increased with acute T cell-mediated rejection (ATCMR; p = 0.030) and higher Banff t and i scores (p < 0.001), and correlated with urinary protein/creatinine ratios (r = 0.450), and inversely with estimated glomerular filtration rate (r =  − 0.604). The area under the receiver operator characteristics curves for urinary DPP-4 concentrations with either Banff t3 or i3 scores were 0.811 (95% confidence interval: 0.687–0.934). The expression of DPP-4 in renal tubular cells was decreased in patients with ATCMR and higher in those with Banff t, i, ct, ci, ah, and ti scores, but was not associated with interstitial fibrosis/tubular atrophy.

Conclusions

We speculated that ATCMR leads to DPP-4 release from tubular cells into urine, resulting in a decrease in tubular cell expression. If so, then ATCMR would induce the elevation of urinary DPP-4 and could therefore serve as a biomarker of tubulitis.

Integrated Immunologic Monitoring in Solid Organ Transplantation: The Road Toward Torque Teno Virus-guided Immunosuppression

Potent immunosuppressive drugs have been introduced into clinical care for solid organ transplant recipients. It is now time to guide these drugs on an individual level to optimize their efficacy. An ideal tool simultaneously detects overimmunosuppression and underimmunosuppression, is highly standardized, and is straightforward to implement into routine. Randomized controlled interventional trials are crucial to demonstrate clinical value. To date, proposed assays have mainly focused on the prediction of rejection and were based on the assessment of few immune compartments. Recently, novel tools have been introduced based on a more integrated approach to characterize the immune function and cover a broader spectrum of the immune system. In this respect, the quantification of the plasma load of a highly prevalent and apathogenic virus that might reflect the immune function of its host has been proposed: the torque teno virus (TTV). Although TTV control is driven by T cells, other major immune compartments might contribute to the hosts' response. A standardized in-house polymerase chain reaction and a conformité européenne-certified commercially available polymerase chain reaction are available for TTV quantification. TTV load is associated with rejection and infection in solid organ transplant recipients, and cutoff values for risk stratification of such events have been proposed for lung and kidney transplantation. Test performance of TTV load does not allow for the diagnosis of rejection and infection but is able to define at-risk patients. Hitherto TTV load has not been used in interventional settings, but two interventional randomized controlled trials are currently testing the safety and efficacy of TTV-guided immunosuppression.

Longitudinal monitoring of mRNA levels of regulatory T cell biomarkers by using non-invasive strategies to predict outcome in renal transplantation

BACKGROUND

Acute T-cell mediated rejection (aTCMR) is still an issue in kidney transplantation, for it is associated with chronic rejection, graft loss, and overall worse outcomes. For these reasons, a standard non-invasive molecular tool to detect is desirable to offer a simpler monitoring of kidney transplant recipients (KTRs). The purpose of our study was to examine, in peripheral blood before and after transplantation, the expression patterns of regulatory T cell (Treg)-related genes: the forkhead box P3 (FOXP3) and the two CTLA-4 isoforms (full-length and soluble) to predict acute rejection onset, de novo donor-specific antibodies (DSA) development and renal dysfunction 1 year after transplantation.

METHODS

We profiled by using a relative quantification analysis (qRT-PCR) circulating mRNA levels of these biomarkers in peripheral blood of 89 KTRs within the first post-transplant year (at baseline and 15, 60 and 365 days, and when possible at the acute rejection) and compared also the results with 24 healthy controls.

RESULTS

The three mRNA levels drastically reduced 15 days after transplantation and gradually recovered at 1 year in comparison with baseline, with very low levels at the time of aTCMR for FOXP3 (RQ = 0.445, IQR = 0.086-1.264, p = 0.040), maybe for the pro-apoptotic role of FOXP3 during inflammation. A multivariate Cox regression analysis evidenced a significant relation between aTCMR onset and thymoglobuline induction (HR = 6.749 p = 0.041), everolimus use (HR = 7.017, p = 0.007) and an increased risk from the solCTLA-4 expression at 15 days, mainly considering recipients treated with Mycophelolic acid (HR = 13.94 p = 0.038, 95%CI:1.157-167.87). Besides, solCTLA-4 also predisposed to graft dysfunction (eGFR< 60 mL/min/1.73m²) at 1 year (AOR = 3.683, 95%CI = 1.145-11.845, p = 0.029). On the other hand, pre-transplant solCTLA-4 levels showed a protective association with de novo DSAs development (HR = 0.189, 95%CI = 0.078-0.459, p < 0.001).

CONCLUSIONS

mRNA levels of Treg-associated genes, mainly for solCTLA-4, in peripheral blood could put forward as candidate non-invasive biomarkers of cellular and humoral alloreactivity in clinical transplantation and might help shape immunosuppression, tailor monitoring and achieve better long-term outcomes of kidney transplantation in the wake of "precision medicine".

Urinary Biomarkers for Kidney Allograft Injury

The current standard of serum creatinine and biopsy to monitor allograft health has many limitations. The most significant drawback of the current standard is the lack of sensitivity and specificity to allograft injuries, which are diagnosed only after significant damage to the allograft. Thus, it is of critical need to identify a biomarker that is sensitive and specific to the early detection of allograft injuries. Urine, as the direct renal ultrafiltrate that can be obtained noninvasively, directly reflects intrarenal processes in the allograft at greater accuracy than analysis of peripheral blood. We review transcriptomic, metabolomic, genomic, and proteomic discovery-based approaches to identifying urinary biomarkers for the noninvasive detection of allograft injuries, as well as the use of urine cell-free DNA in the QSant urine assay as a sensitive surrogate for the renal allograft biopsy for rejection diagnosis.

Expanding the Non-Invasive Diagnosis of Acute Rejection in Kidney Transplants Through Detection of Donor-Derived DNA in Urine: Proof-of-Concept Study

Background

Approximately 10%-20% of kidney transplant (KT) recipients suffer from acute rejection (AR); thus, sensitive and accurate monitoring of allograft status is recommended. We evaluated the clinical utility of donor-derived DNA (dd-DNA) detection in the urine of KT recipients as a non-invasive means for diagnosing AR.

Methods

Urine samples serially collected from 39 KT recipients were tested for 39 single-nucleotide variant loci selected according to technical criteria (i.e., high minor allele frequency and low analytical error) using next-generation sequencing. The fraction of dd-DNA was calculated and normalized by the urine creatinine (UCr) level (%dd-DNA/UCr). The diagnostic performance of %dd-DNA/UCr for AR was assessed by ROC curve analysis.

Results

There was an increasing trend of %dd-DNA/UCr in the AR group before subsequent graft injury, which occurred before (median of 52 days) histological rejection. The serum creatinine (SCr) level differed significantly between the AR and non-AR groups at two and four months of follow-up, whereas %dd-DNA/UCr differed between the groups at six months of follow-up. The combination of %dd-DNA/UCr, SCr, and spot urine protein (UPtn)/UCr showed high discriminating power, with an area under the ROC curve of 0.93 (95% confidence interval: 0.81-1.00) and a high negative predictive value of 100.0%.

Conclusions

Although the dd-DNA-based test cannot eliminate the need for biopsy, the high negative predictive value of this marker could increase the prebiopsy probability of detecting treatable injury to make biopsy an even more effective diagnostic tool.

Investigating the Role of BAFF and Its Receptors in Renal Transplant Recipients with Chronic Antibody-Mediated Rejection

Background

Kidney transplantation is the best treatment option for end stage renal disease (ESRD), but graft rejection is still a big obstacle that occurs in spite of immunosuppressive therapy. B cells are considered as the major reason for renal graft rejection because of antibody production. Due to their roles in B cell function, we intended to evaluate the B cell activating factor (BAFF) and its receptors including BAFF receptor (BAFF-R), B cell maturation antigen (BCMA), and transmembrane activator and cyclophilin ligand interactor (TACI) in renal transplant patients.

Method

The study included 40 kidney allograft patients with cAMR, 40 stable kidney allograft patients, and 8 healthy volunteers with normal kidney function. The percentage and absolute number of CD19⁺ B cells were analyzed by flow cytometry, the serum level of BAFF was analyzed by ELISA, and mRNA expressions of BAFF and BAFF receptors (BAFF-R, BCMA, and TACI) were measured using quantitative real-time PCR.

Results

The percentage and the absolute number of B cells decreased significantly in stable and cAMR patients compared to healthy individuals. The serum level and gene expression of BAFF, as well as the mRNA level of BCMA, were increased significantly in both cAMR and stable patients compared to healthy volunteers. There was an overexpression of TACI mRNA in cAMR patients compared to stable patients.

Conclusions

Both soluble protein and mRNA transcript of BAFF increased in transplant recipients. However, BAFF neither at the serum level nor at the mRNA transcript level cannot be a good biomarker for the prediction of cAMR. In addition, expression of TACI, compared to other receptors of BAFF, confers a potential to be used in distinguishing cAMR and stable kidney transplant patients.

A Practical Guide to the Clinical Implementation of Biomarkers for Subclinical Rejection Following Kidney Transplantation

Noninvasive biomarkers are needed to monitor stable patients following kidney transplantation (KT), as subclinical rejection, currently detectable only with invasive surveillance biopsies, can lead to chronic rejection and graft loss. Several biomarkers have recently been developed to detect rejection in KT recipients, using different technologies as well as varying clinical monitoring strategies defined as "context of use (COU)." The various metrics utilized to evaluate the performance of each biomarker can also vary, depending on their intended COU. As the use of molecular biomarkers in transplantation represents a new era in patient management, it is important for clinicians to better understand the process by which the incremental value of each biomarkers is evaluated to determine its potential role in clinical practice. This process includes but is not limited to an assessment of clinical validity and utility, but to define these, the clinician must first appreciate the trajectory of a biomarker from bench to bedside as well as the regulatory and other requirements needed to navigate this course successfully. This overview summarizes this process, providing a framework that can be used by clinicians as a practical guide in general, and more specifically in the context of subclinical rejection following KT. In addition, we have reviewed available as well as promising biomarkers for this purpose in terms of the clinical need, COU, assessment of biomarker performance relevant to both the need and COU, assessment of biomarker benefits and risks relevant to the COU, and the evidentiary criteria of the biomarker relevant to the COU compared with the current standard of care. We also provide an insight into the path required to make biomarkers commercially available once they have been developed and validated so that they used by clinicians outside the research context in every day clinical practice.

Targeted Urine Metabolomics for Monitoring Renal Allograft Injury and Immunosuppression in Pediatric Patients

Despite new advancements in surgical tools and therapies, exposure to immunosuppressive drugs related to non-immune and immune injuries can cause slow deterioration and premature failure of organ transplants. Diagnosis of these injuries by non-invasive urine monitoring would be a significant clinical advancement for patient management, especially in pediatric cohorts. We investigated the metabolomic profiles of biopsy matched urine samples from 310 unique kidney transplant recipients using gas chromatography-mass spectrometry (GC-MS). Focused metabolite panels were identified that could detect biopsy confirmed acute rejection with 92.9% sensitivity and 96.3% specificity (11 metabolites) and could differentiate BK viral nephritis (BKVN) from acute rejection with 88.9% sensitivity and 94.8% specificity (4 metabolites). Overall, targeted metabolomic analyses of biopsy-matched urine samples enabled the generation of refined metabolite panels that non-invasively detect graft injury phenotypes with high confidence. These urine biomarkers can be rapidly assessed for non-invasive diagnosis of specific transplant injuries, opening the window for precision transplant medicine.

Identification of Candidate Biomarkers for Transplant Rejection from Transcriptome Data: A Systematic Review

BACKGROUND

Traditional methods for rejection control in transplanted patients are considered invasive, risky, and prone to sampling errors. Using molecular biomarkers as an alternative protocol to biopsies, for monitoring rejection may help to mitigate some of these problems, increasing the survival rates and well-being of patients. Recent advances in omics technologies provide an opportunity for screening new molecular biomarkers to identify those with clinical utility.

OBJECTIVE

This systematic literature review (SLR) aimed to summarize existing evidence derived from large-scale expression profiling regarding differentially expressed mRNA and miRNA in graft rejection, highlighting potential molecular biomarkers in transplantation.

METHODS

The study was conducted following PRISMA methodology and the BiSLR guide for performing SLR in bioinformatics. PubMed, ScienceDirect, and EMBASE were searched for publications from January 2001 to January 2018, and studies (i) aiming at the identification of transplant rejection biomarkers, (ii) including human subjects, and (iii) applying methodologies for differential expression analysis from large-scale expression profiling were considered eligible. Differential expression patterns reported for genes and miRNAs in rejection were summarized from both cross-organ and organ-specific perspectives, and pathways enrichment analysis was performed for candidate biomarkers to interrogate their functional role in transplant rejection.

RESULTS

A total of 821 references were collected, resulting in 604 studies after removal of duplicates. After application of inclusion and exclusion criteria, 33 studies were included in our analysis. Among the 1517 genes and 174 miRNAs identifed, CXCL9, CXCL10, STAT1, hsa-miR-142-3p, and hsa-miR-155 appeared to be particularly promising as biomarkers in transplantation, with an increased expression associated with transplant rejection in multiple organs. In addition, hsa-miR-28-5p was consistently decreased in samples taken from rejected organs.

CONCLUSION

Despite the need for further research to fill existing knowledge gaps, transcriptomic technologies have a relevant role in the discovery of accurate biomarkers for transplant rejection diagnostics. Studies have reported consistent evidence of differential expression associated with transplant rejection, although issues such as experimental heterogeneity hinder a more systematic characterization of observed molecular changes. Special attention has been giving to large-scale mRNA expression profiling in rejection, whereas there is still room for improvements in the characterization of miRnome in this condition.

PROSPERO REGISTRATION NUMBER

CRD42018083321.

Pathology of the kidney allograft

The kidney biopsy still represents the best approach to diagnose renal transplant complications. It is considered the gold standard in the diagnosis of rejection and non-rejection complications. Although invasive, it is a safe procedure with a very low complication rate. With adequate sampling, changes related to antibody-mediated rejection (ABMR) and T-cell mediated rejection (TCMR) can be identified. However, the pathologist needs to be aware of the many other complications, not related to rejection, that can affect the allograft function. Examples include viral infections, drug toxicity, systemic diseases such as hypertension and diabetes, and recurrent or de novo glomerulopathy, among others. In this article, we review the recent classification of pathology of the kidney allograft, with reference to recent consensus reached at the most recent Banff renal allograft classification meetings, and also highlight common non-rejection complications of the kidney transplant.

Assessment of 19 Genes and Validation of CRM Gene Panel for Quantitative Transcriptional Analysis of Molecular Rejection and Inflammation in Archival Kidney Transplant Biopsies

Background: There is an urgent need to develop and implement low cost, high-throughput standardized methods for routine molecular assessment of transplant biopsies. Given the vast archive of formalin-fixed and paraffin-embedded (FFPE) tissue blocks in transplant centers, a reliable protocol for utilizing this tissue bank for clinical validation of target molecules as predictors of graft outcome over time, would be of great value.

Methods: We designed and optimized assays to quantify 19 target genes, including previously reported set of tissue common rejection module (tCRM) genes. We interrogated their performance for their clinical utility for detection of graft rejection and inflammation by analyzing gene expression microarrays analysis of 163 renal allograft biopsies, and subsequently validated in 40 independent FFPE archived kidney transplant biopsies at a single center.

Results: A QPCR (Fluidigm) and a barcoded oligo-based (NanoString) gene expression platform were compared for evaluation of amplification of gene expression signal for 19 genes from degraded RNA extracted from FFPE biopsy sections by a set protocol. Increased expression of the selected 19 genes, that reflect a combination of specific cellular infiltrates (8/19 genes) and a graft inflammation score (11/19 genes which computes the tCRM score allowed for segregation of kidney transplant biopsies with stable allograft function and normal histology from those with histologically confirmed acute rejection (AR; p = 0.0022, QPCR; p = 0.0036, barcoded assay) and many cases of histological borderline inflammation (BL). Serial biopsy shaves used for gene expression were also processed for in-situ hybridization (ISH) for a subset of genes. ISH confirmed a high degree of correlation of signal amplification and tissue localization.

Conclusions: Target gene expression amplification across a custom set of genes can identify AR independent of histology, and quantify inflammation from archival kidney transplant biopsy tissue, providing a new tool for clinical correlation and outcome analysis of kidney allografts, without the need for prospective kidney biopsy biobanking efforts.

Urinary nanosensors of early transplant rejection

Nanoparticle sensors of the activity of the protease granzyme B detect early T-cell-mediated rejection of transplanted skin grafts in mice via the release of a proteolytically cleaved fluorescence reporter that filters into urine.

Clinical Operational Tolerance and Immunosuppression Minimization in Kidney Transplantation: Where Do We Stand?

BACKGROUND

The 20th century represents a breakthrough in the transplantation era, since the first kidney transplantation between identical twins was performed. This was the first case of tolerance, since the recipient did not need immunosuppression. However, as transplantation became possible, an immunosuppression-free status became the ultimate goal, since the first tolerance case was a clear exception from the hard reality nowadays represented by rejection.

METHODS

A plethora of studies was described over the past decades to understand the molecular mechanisms responsible for rejection. This review focuses on the most relevant studies found in the literature where renal tolerance cases are claimed. Contrasting, and at the same time, encouraging outcomes are herein discussed and a glimpse on the main renal biomarkers analyzed in this field is provided.

RESULTS

The activation of the immune system has been shown to play a central role in organ failure, but also it seems to induce a tolerance status when an allograft is performed, despite tolerance is still rare to register. Although there are still overwhelming challenges to overcome and various immune pathways remain arcane; the immunosuppression minimization might be more attainable than previously believed.

CONCLUSION

. Multiple biomarkers and tolerance mechanisms suspected to be involved in renal transplantation have been investigated to understand their real role, with still no clear answers on the topic. Thus, the actual knowledge provided necessarily leads to more in-depth investigations, although many questions in the past have been answered, there are still many issues on renal tolerance that need to be addressed.

Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio Predict Acute Cellular Rejection in the Kidney Allograft

Background

Kidney transplantation is the treatment of choice for end stage kidney disease, but acute rejection remains a limiting factor in optimizing allograft and patient survival. Needle biopsy is the current standard of care for this diagnosis. The potential for complications with repeat biopsies limits the ability to obtain temporal immune surveillance of the allograft. The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been shown to be strong predictors of inflammation and of worse prognosis in a variety of conditions.

Material/Methods

This is a single center retrospective case control study which included all patients who underwent a “for -cause biopsy” of a transplanted kidney. NLR and PLR were calculated 1 month prior, at the time, and 6 months and 1 year after the biopsy.

Results

A total of 159 biopsies were reviewed; 127 (79.9%) of these satisfied all inclusion and exclusion criteria, and 63.0% of the sample cohort (n=80) demonstrated acute cellular rejection (ACR). Patients without evidence of ACR had an average NLR of 26.8, which was approximately 7-fold greater than those patients with findings of ACR (P<0.01). A similar trend was found for PLR, where patients without ACR had a 5.5-fold greater PLR compared to those with rejection (P<0.01). The ROC showed AUC of 0.715 and 0.716 respectively. The NLR cutoff of 9.5 had a positive predictive value (PPV) of 80% and a negative predictive value (NPV) of 77.8%; the PLR cutoff of 380 had a PPV of 75% and a NPV of 100%.

Conclusions

This study showed that NLR and PLR are easily obtainable and reproducible predictors of ACR in the kidney allograft. Serial monitoring of these ratios will help identify subclinical inflammation before evidence of allograft dysfunction.