Interleukin-6 expression after renal transplantation

Impact of interleukin-6 on T cells in kidney transplant recipients

Interleukin-6 (IL-6), a multifunctional proinflammatory cytokine, plays a key role in T cell activation, survival, and differentiation. Acting as a switch that induces the differentiation of naïve T cells into Th17 cells and inhibits their development into regulatory T cells, IL-6 promotes rejection and abrogates tolerance. Therapies that target IL-6 signaling include antibodies to IL-6 and the IL-6 receptor and inhibitors of janus kinases; several of these therapeutics have demonstrated robust clinical efficacy in autoimmune and inflammatory diseases. Clinical trials of IL-6 inhibition in kidney transplantation have focused primarily on its effects on B cells, plasma cells, and HLA antibodies. In this review, we summarize the impact of IL-6 on T cells in experimental models of transplant and describe the effects of IL-6 inhibition on the T cell compartment in kidney transplant recipients.

Long term tolerability and clinical outcomes associated with tocilizumab in the treatment of refractory antibody mediated rejection (AMR) in pediatric renal transplant recipients

BACKGROUND

Treatment options for antibody-mediated rejection (AMR) are limited. Recent studies have shown that inhibition of interleukin-6 (IL-6)/interleukin-6 receptor (IL-6R) signaling can reduce inflammation and slow AMR progression.

METHODS

We report our experience using monthly tocilizumab (anti-IL6R) in 25 pediatric renal transplant recipients with AMR, refractory to IVIg/Rituximab. From January 2013 to June 2019, a median (IQR) of 12 (6.019.0) doses of tocilizumab were given per patient. Serial assessments of renal function, biopsy findings, and HLA DSA (by immunodominant HLA DSA [iDSA] and relative intensity score [RIS]) were performed.

RESULTS

Median (IQR) time from transplant to AMR was 41.4 (24.367.7) months, and time from AMR to first tocilizumab was 10.6 (8.317.6) months. At median (IQR) follow up of 15.8 (8.435.7) months post-tocilizumab initiation, renal function was stable except for 1 allograft loss. There was no significant decrease in iDSA or RIS. Follow up biopsies showed reduction in peritubular capillaritis (p = .015) and C4d scoring (p = .009). The most frequent adverse events were cytopenias.

CONCLUSIONS

Tocilizumab in pediatric patients with refractory AMR was well tolerated and appeared to stabilize renal function. The utility of tocilizumab in the treatment of AMR in this population should be further explored.

Chronic Kidney Disease-Mineral Bone Disease biomarkers in kidney transplant patients

Background:

Chronic Kidney Disease associated with Mineral Bone Disease (CKD-MBD) is frequent in kidney transplant patients. Post-transplantation bone disease is complex, especially in patients with pre-existing metabolic bone disorders that are further affected by immunosuppressive medications and changes in renal allograft function. Main biochemical abnormalities of mineral metabolism in kidney transplantation (KTx) include hypophosphatemia, hyperparathyroidism (HPTH), insufficiency or deficiency of vitamin D, and hypercalcemia.

Objective:

This review aimed to summarize the pathophysiology and main biomarkers of CKD-MBD in KTx.

Methods:

A comprehensive and non-systematic search in PubMed was independently made with an emphasis on biomarkers in mineral bone disease in KTx.

Results:

CKD-MBD can be associated with numerous factors including secondary HPTH, metabolic dysregulations before KTx, and glucocorticoids therapy in post-transplant subjects. Fibroblast growth factor 23 (FGF23) reaches normal levels after KTx with good allograft function, while calcium, vitamin D and phosphorus, ultimately, result in hypercalcemia, persistent vitamin D insufficiency, and hypophosphatemia respectively. As for PTH levels, there is an initial tendency of a significant decrease, followed by a raise due to secondary or tertiary HPTH. In regard to sclerostin levels, there is no consensus in the literature.

Conclusion:

KTx patients should be continuously evaluated for mineral homeostasis and bone status, both cases with successful kidney transplantation and those with reduced functionality. Additional research on CKD-MBD pathophysiology, diagnosis, and management is essential to guarantee long-term graft function, better prognosis, good quality of life, and reduced mortality for KTx patients.

The Impact of Inflammation on the Immune Responses to Transplantation: Tolerance or Rejection?

Transplantation (Tx) remains the optimal therapy for end-stage disease (ESD) of various solid organs. Although alloimmune events remain the leading cause of long-term allograft loss, many patients develop innate and adaptive immune responses leading to graft tolerance. The focus of this review is to provide an overview of selected aspects of the effects of inflammation on this delicate balance following solid organ transplantation. Initially, we discuss the inflammatory mediators detectable in an ESD patient. Then, the specific inflammatory mediators found post-Tx are elucidated. We examine the reciprocal relationship between donor-derived passenger leukocytes (PLs) and those of the recipient, with additional emphasis on extracellular vesicles, specifically exosomes, and we examine their role in determining the balance between tolerance and rejection. The concept of recipient antigen-presenting cell "cross-dressing" by donor exosomes is detailed. Immunological consequences of the changes undergone by cell surface antigens, including HLA molecules in donor and host immune cells activated by proinflammatory cytokines, are examined. Inflammation-mediated donor endothelial cell (EC) activation is discussed along with the effect of donor-recipient EC chimerism. Finally, as an example of a specific inflammatory mediator, a detailed analysis is provided on the dynamic role of Interleukin-6 (IL-6) and its receptor post-Tx, especially given the potential for therapeutic interdiction of this axis with monoclonal antibodies. We aim to provide a holistic as well as a reductionist perspective of the inflammation-impacted immune events that precede and follow Tx. The objective is to differentiate tolerogenic inflammation from that enhancing rejection, for potential therapeutic modifications. (Words 247).

Cardiac allograft vasculopathy: current review and future research directions

Cardiac allograft vasculopathy (CAV) is a pathologic immune-mediated remodelling of the vasculature in transplanted hearts and, by impairing perfusion, is the major cause of late graft loss. Although best understood following cardiac transplantation, similar forms of allograft vasculopathy occur in other vascularized organ grafts and some features of CAV may be shared with other immune-mediated vasculopathies. Here, we describe the incidence and diagnosis, the nature of the vascular remodelling, immune and non-immune contributions to pathogenesis, current therapies, and future areas of research in CAV.

Anti-interleukin-6 antibody clazakizumab in late antibody-mediated kidney transplant rejection: effect on cytochrome P450 drug metabolism

Targeting interleukin-6 (IL-6) is a promising strategy to counteract antibody-mediated rejection (ABMR). In inflammatory states, IL-6 antagonism was shown to modulate cytochrome P450 (CYP), but its impact on drug metabolism in ABMR treatment was not addressed so far. We report a sub-study of a phase 2 trial of anti-IL-6 antibody clazakizumab in late ABMR (ClinicalTrials.gov, NCT03444103). Twenty kidney transplant recipients were randomized to clazakizumab versus placebo (4-weekly doses; 12 weeks), followed by a 9-month extension where all recipients received clazakizumab. To study CYP2C19/CYP3A4 metabolism, we administered pantoprazole (20 mg intravenously) at prespecified time points. Dose-adjusted C₀ levels (C₀ /D ratio) of tacrolimus (n = 13) and cyclosporin A (CyA, n = 6) were monitored at 4-weekly intervals. IL-6 and C-reactive protein were not elevated at baseline, the latter was then suppressed to undetectable levels under clazakizumab. IL-6 blockade had no clinically meaningful impact on pantoprazole pharmacokinetics (area under the curve; baseline versus week 52: 3.16 [2.21-7.84] versus 4.22 [1.99-8.18] μg/ml*h, P = 0.36) or calcineurin inhibitor C₀ /D ratios (tacrolimus: 1.49 [1.17-3.20] versus 1.37 [0.98-2.42] ng/ml/mg, P = 0.21; CyA: 0.69 [0.57-0.85] versus 1.08 [0.52-1.38] ng/ml/mg, P = 0.47). We conclude that IL-6 blockade in ABMR - in absence of systemic inflammation - may have no meaningful effect on CYP metabolism.

IL-6 Directed Therapy in Transplantation

Purpose of Review

IL-6 is a pleiotropic, pro-inflammatory cytokine that plays an integral role in the development of acute and chronic rejection after solid organ transplantation. This article reviews the experimental evidence and current clinical application of IL-6/IL-6 receptor (IL-6R) signaling inhibition for the prevention and treatment of allograft injury.

Recent Findings

There exists a robust body of evidence linking IL-6 to allograft injury mediated by acute inflammation, adaptive cellular/humoral responses, innate immunity, and fibrosis. IL-6 promotes the acute phase reaction, induces B cell maturation/antibody formation, directs cytotoxic T-cell differentiation, and inhibits regulatory T-cell development. Importantly, blockade of the IL-6/IL-6R signaling pathway has been shown to mitigate its harmful effects in experimental studies, particularly in models of kidney and heart transplant rejection. Currently, available agents for IL-6 signaling inhibition include monoclonal antibodies against IL-6 or IL-6R and janus kinase inhibitors. Recent clinical trials have investigated the use of tocilizumab, an anti-IL-6R mAb, for desensitization and treatment of antibody-mediated rejection (AMR) in kidney transplant recipients, with promising initial results. Further studies are underway investigating the use of alternative agents including clazakizumab, an anti-IL-6 mAb, and application of IL-6 signaling blockade to clinical cardiac transplantation.

Summary

IL-6/IL-6R signaling inhibition provides a novel therapeutic option for the prevention and treatment of allograft injury. To date, evidence from clinical trials supports the use of IL-6 blockade for desensitization and treatment of AMR in kidney transplant recipients. Ongoing and future clinical trials will further elucidate the role of IL-6 signaling inhibition in other types of solid organ transplantation.

A Randomized Clinical Trial of Anti-IL-6 Antibody Clazakizumab in Late Antibody-Mediated Kidney Transplant Rejection

BACKGROUND

Late antibody-mediated rejection (ABMR) is a leading cause of transplant failure. Blocking IL-6 has been proposed as a promising therapeutic strategy.

METHODS

We performed a phase 2 randomized pilot trial to evaluate the safety (primary endpoint) and efficacy (secondary endpoint analysis) of the anti-IL-6 antibody clazakizumab in late ABMR. The trial included 20 kidney transplant recipients with donor-specific, antibody-positive ABMR ≥365 days post-transplantation. Patients were randomized 1:1 to receive 25 mg clazakizumab or placebo (4-weekly subcutaneous injections) for 12 weeks (part A), followed by a 40-week open-label extension (part B), during which time all participants received clazakizumab.

RESULTS

Five (25%) patients under active treatment developed serious infectious events, and two (10%) developed diverticular disease complications, leading to trial withdrawal. Those receiving clazakizumab displayed significantly decreased donor-specific antibodies and, on prolonged treatment, modulated rejection-related gene-expression patterns. In 18 patients, allograft biopsies after 51 weeks revealed a negative molecular ABMR score in seven (38.9%), disappearance of capillary C4d deposits in five (27.8%), and resolution of morphologic ABMR activity in four (22.2%). Although proteinuria remained stable, the mean eGFR decline during part A was slower with clazakizumab compared with placebo (-0.96; 95% confidence interval [95% CI], -1.96 to 0.03 versus -2.43; 95% CI, -3.40 to -1.46 ml/min per 1.73 m2 per month, respectively, P=0.04). During part B, the slope of eGFR decline for patients who were switched from placebo to clazakizumab improved and no longer differed significantly from patients initially allocated to clazakizumab.

CONCLUSIONS

Although safety data indicate the need for careful patient selection and monitoring, our preliminary efficacy results suggest a potentially beneficial effect of clazakizumab on ABMR activity and progression.

Evaluation of Renal Anionic Secretion Following Living-donor and Deceased-donor Renal Transplantation: A Clinical Pharmacokinetic Study of Cefoxitin Microdosing

Renal transplantation is the treatment of choice for patients with end-stage renal disease. Because kidneys are the primary excretory organs for various drugs/drug metabolites, changes in renal graft function would significantly alter the clearance and exposure of renally secreted drugs. Renal allografts from living and deceased donors normally undergo numerous insults, including injuries associated with prolonged cold ischemic time, reperfusion, and nephrotoxicity due to calcineurin inhibitors. These physiologic and pharmacologic stresses can alter the expression and functional capacity of renal organic anionic transporters (OATs).

Methods

The objectives of this study were to assess the longitudinal changes in renal anionic secretion in kidney transplant patients, to study the effect of prolonged cold ischemic time on OAT secretion in kidney transplant patients (living- versus deceased-donor recipients), and to compare OAT secretory capacity of renal transplant recipients with healthy volunteers. Cefoxitin was used as a probe drug to assess OAT secretion. Cefoxitin pharmacokinetics was studied in 15 de novo renal transplant recipients following intravenous administration of 200 mg cefoxitin within 14 d and beyond 90 d posttransplantation.

Results

No longitudinal changes in real OAT secretion in early posttransplant period were observed, and there were no differences in renal OAT secretion between living- and deceased-donor renal transplant recipients. Overall, cefoxitin exposure was 2.6-fold higher and half-life increased by 2.2-fold in renal transplant recipients when compared with historical healthy controls.

Conclusions

These results suggest that OAT system is functioning well, but renal transplant recipients would need significantly lower dosage of drugs that are primarily secreted via the OAT system compared with normal subjects.

Tocilizumab in transplantation

PURPOSE

Tocilizumab, a monoclonal antibody directed against the IL-6 receptor, might block detrimental effects of IL-6 on transplantation. IL-6 plays a considerable role in cytokine storm after stem cell transplantation as well as graft versus host disease, and it has also been shown to be involved in solid organ allograft rejection; therefore, tocilizumab is expected to promote graft survival. Nonetheless, due to the small number of studies and disparate methods of drug administration and outcome evaluation, for which types of transplantation, at which stages, and to what extent tocilizumab could be applied remains to be defined.

METHODS

The Pubmed, SCOPUS and Google Scholar search engines were used to collect data. The keywords were determined by Pubmed MeSH. No time limitation was set and all types of articles were allowed.  RESULTS: According to the potential of Tocilozumab in controlling both cellular and humoral immunity it could be considered as a promising agent in tolerance induction; however, blocking IL-6 signaling might result in augmented infection rate in recipients.

CONCLUSION

The need for providing effective and safe immunosuppressive agents to protect transplanted cells and organs against allo-reactivity urges the collection and discussion of all available findings about inhibition of determining immune components including cytokines; herein, we have summarized the clinical consequences of blocking IL-6 by tocilizumab in stem cell and solid organ transplantations.

Targeting the mTOR pathway uncouples the efficacy and toxicity of PD-1 blockade in renal transplantation

Immune checkpoint inhibitor (ICI) use remains a challenge in patients with solid organ allografts as most would undergo rejection. In a melanoma patient in whom programmed-death 1 (PD-1) blockade resulted in organ rejection and colitis, the addition of the mTOR inhibitor sirolimus resulted in ongoing anti-tumor efficacy while promoting allograft tolerance. Strong granzyme B⁺, interferon (IFN)-γ⁺ CD8⁺ cytotoxic T cell and circulating regulatory T (T_reg) cell responses were noted during allograft rejection, along with significant eosinophilia and elevated serum IL-5 and eotaxin levels. Co-treatment with sirolimus abated cytotoxic T cell numbers and eosinophilia, while elevated T_reg cell numbers in the peripheral blood were maintained. Interestingly, numbers of IFN-γ⁺ CD4⁺ T cells and serum IFN-γ levels increased with the addition of sirolimus treatment likely promoting ongoing anti-PD-1 efficacy. Thus, our results indicate that sirolimus has the potential to uncouple anti-PD-1 therapy toxicity and efficacy.

The use of immune checkpoint inhibitors (ICI) in cancer patients with solid organ allografts is hampered due to potential organ rejection. Here, the authors present a case report of a patient with kidney allograft and show that treatment with the mTOR inhibitor sirolimus preserves peripheral tolerance and anti-tumour efficacy of ICI therapy.

Treg-mediated prolonged survival of skin allografts without immunosuppression

Injection of Interleukin-2 (IL-2) complexed with a particular anti-IL-2 monoclonal antibody (mab) JES6-1 has been shown to selectively expand CD4⁺Foxp3⁺ T regulatory T cells (Tregs) in vivo. Although the potency of this approach with regard to transplantation has already been proven in an islet transplantation model, skin graft survival could not be prolonged. Since the latter is relevant to human allograft survival, we sought to improve the efficiency of IL-2 complex (cplx) treatment for skin allograft survival in a stringent murine skin graft model. Here, we show that combining low doses of IL-2 cplxs with rapamycin and blockade of the inflammatory cytokine IL-6 leads to long-term (>75 d) survival of major histocompatibility complex-different skin allografts without the need for immunosuppression. Allograft survival was critically dependent on CD25⁺FoxP3⁺ Tregs and was not accompanied by impaired responsiveness toward donor alloantigens in vitro after IL-2 cplx treatment was stopped. Furthermore, second donor-type skin grafts were rejected and provoked rejection of the primary graft, suggesting that operational tolerance is not systemic but restricted to the graft. These findings plus the lack of donor-specific antibody formation imply that prolonged graft survival was largely a reflection of immunological ignorance. The results may represent a potentially clinically translatable strategy for the development of protocols for tolerance induction.

Evaluation of Serum Interleukin-6 Levels in the Renal Transplant Recipients: A Systematic Review and Meta-Analysis of Case-Control Studies

AIM:

The purpose of this meta-analysis was the assessment of the serum IL-6 levels in the renal transplant recipients compared to the healthy controls.

MATERIAL AND METHODS:

Four databases including PubMed, Web of Science, Scopus, and Cochrane Library were searched up to July 2018 without language restriction. The quality of studies was evaluated using the Newcastle-Ottawa scale (NOS). A continuous random-effects meta-analysis was used by RevMan 5.3 using the mean difference (MD) and 95% confidence intervals (CIs). Also, a regression model was done by Comprehensive Meta-Analysis version 2 (CMA v2).

RESULTS:

Out of 615 studies identified in the databases, 15 studies included and analysed in the meta-analysis. The studies were reported from 1994 to 2018. The meta-analysis included 1035 renal transplant recipients and 682 healthy controls. The pooled MD of the serum IL-6 levels in the transplant recipients compared to the healthy controls was 3.25 pg/mL [95%CI: 2.17, 4.32; P < 0.00001; I2 = 98% (P < 0.00001)]. Meta-regression analysis showed that one of the reasons of heterogeneity is the year of publication (Correlation coefficient (r) = 0.208, p-value = 0.00002).

CONCLUSION:

An elevated serum IL-6 level in the renal transplant recipients compared to the healthy controls showed that the serum level of this marker could be used for the evaluation of inflammation in ESRD patients undergoing renal transplantation.

Cytokine Profiles Associated With Angiotensin II Type 1 Receptor Antibodies

Introduction

Angiotensin II type 1 receptor antibody (AT1R-Ab), is a non–human leukocyte antigen (HLA) antibody implicated in poor renal allograft outcomes, although its actions may be mediated through a different pathway than HLA donor-specific antibodies (DSAs). Our aim was to examine serum cytokine profiles associated with AT1R-Ab and distinguish them from those associated with HLA DSA in serially collected blood samples from a cohort of pediatric renal transplant recipients.

Methods

Blood samples from 65 pediatric renal transplant recipients drawn during the first 3 months posttransplant, at 6, 12, and 24 months posttransplant, and during suspected episodes of kidney transplant rejection were tested for AT1R-Ab, HLA DSA, and a panel of 6 cytokines (tumor necrosis factor [TNF]-α, interferon [IFN]-γ, interleukin [IL]-8, IL-1β, IL-6, and IL-17). Associations between antibodies and cytokines were evaluated.

Results

AT1R-Ab, but not HLA DSA, was associated with elevations in TNF-α, IFN-γ, IL-8, IL-1β, IL-6, and IL-17. This relationship remained significant even after controlling for relevant clinical factors and was consistent across all time points. In contrast to HLA DSA, AT1R-Ab was associated with elevations in vascular inflammatory cytokines in the first 2 years posttransplant.

Conclusions

This profile of vascular cytokines may be informative for clinical monitoring and designing future studies to delineate the distinct pathophysiology of AT1R-Ab–mediated allograft injury in kidney transplantation.

Impact of Immune-Modulatory Drugs on Regulatory T Cell

Immunosuppression strategies that selectively inhibit effector T cells while preserving and even enhancing CD4FOXP3 regulatory T cells (Treg) permit immune self-regulation and may allow minimization of immunosuppression and associated toxicities. Many immunosuppressive drugs were developed before the identity and function of Treg were appreciated. A good understanding of the interactions between Treg and immunosuppressive agents will be valuable to the effective design of more tolerable immunosuppression regimens. This review will discuss preclinical and clinical evidence regarding the influence of current and emerging immunosuppressive drugs on Treg homeostasis, stability, and function as a guideline for the selection and development of Treg-friendly immunosuppressive regimens.

Ex Vivo Normothermic Perfusion Induces Donor-Derived Leukocyte Mobilization and Removal Prior to Renal Transplantation

Introduction

Ex vivo normothermic perfusion offers an alternative method of organ preservation, allowing donor kidneys to be reanimated and evaluated prior to transplantation. Beyond preservation, it can be used to characterize the immunological contribution of the donor kidney in isolation. Furthermore, it has the potential to be used as an immunomodulatory strategy to manipulate donor kidneys prior to transplantation.

Methods

Explanted porcine kidneys underwent 6 hours of perfusion. Sequential perfusate samples were collected and leukocytes characterized via flow cytometry. An inflammatory profile was generated via cytokine quantification. Cell-free DNA was also determined as markers of cell death.

Results

All kidneys functioned within normal parameters and met the criteria for transplantation at the end of perfusion. Throughout perfusion there were continuous increases in pro-inflammatory cytokines, including large concentrations of interferon-γ, suggesting that perfusion drives a significant inflammatory response. Increasing concentrations in cell-free DNA were also observed, suggesting cell death. During perfusion there was a marked cellular diapedesis of T cells, B cells, natural killer (NK) cells, and monocytes from the kidney into the circuit. Minor populations of granulocytes and macrophages were also detected.

Discussion

We demonstrate that ex vivo normothermic perfusion initiates an inflammatory cytokine storm and release of mitochondrial and genomic DNA. This is likely to be responsible for immune cell activation and mobilization into the circuit prior to transplantation. Interestingly this did not have an impact on renal function. These data therefore suggest that normothermic perfusion can be used to immunodeplete and to saturate the pro-inflammatory capacity of donor kidneys prior to transplantation.

Recipient Myd88 Deficiency Promotes Spontaneous Resolution of Kidney Allograft Rejection

The myeloid differentiation protein 88 (MyD88) adapter protein is an important mediator of kidney allograft rejection, yet the precise role of MyD88 signaling in directing the host immune response toward the development of kidney allograft rejection remains unclear. Using a stringent mouse model of allogeneic kidney transplantation, we demonstrated that acute allograft rejection occurred equally in MyD88-sufficient (wild-type [WT]) and MyD88(-/-) recipients. However, MyD88 deficiency resulted in spontaneous diminution of graft infiltrating effector cells, including CD11b(-)Gr-1(+) cells and activated CD8 T cells, as well as subsequent restoration of near-normal renal graft function, leading to long-term kidney allograft acceptance. Compared with T cells from WT recipients, T cells from MyD88(-/-) recipients failed to mount a robust recall response upon donor antigen restimulation in mixed lymphocyte cultures ex vivo. Notably, exogenous IL-6 restored the proliferation rate of T cells, particularly CD8 T cells, from MyD88(-/-) recipients to the proliferation rate of cells from WT recipients. Furthermore, MyD88(-/-) T cells exhibited diminished expression of chemokine receptors, specifically CCR4 and CXCR3, and the impaired ability to accumulate in the kidney allografts despite an otherwise MyD88-sufficient environment. These results provide a mechanism linking the lack of intrinsic MyD88 signaling in T cells to the effective control of the rejection response that results in spontaneous resolution of acute rejection and long-term graft protection.

Inflammation-Induced IL-6 Functions as a Natural Brake on Macrophages and Limits GN

IL-6 can mediate proinflammatory effects, and IL-6 receptor (IL-6R) blockade as a treatment for inflammatory diseases has entered clinical practice. However, opposing effects of IL-6 have been observed in models of GN. Although IL-6 is proinflammatory in murine lupus nephritis, protective effects have been observed for IL-6 in the nephrotoxic nephritis (NTN) model of acute crescentic GN. In light of the potential dangers of IL-6-directed treatment, we studied the mechanisms underlying the contradictory findings in GN. IL-6 can signal through the membrane-bound IL-6R, which is expressed only on hepatocytes and certain leukocytes (classic), or through the soluble IL-6R, which binds the ubiquitously expressed gp130 (alternative). Preemptive treatment of mice with anti-IL-6R or anti-IL-6 worsened NTN, whereas selective blockade of alternative IL-6 signaling by the fusion protein sgp130Fc did not. FACS analysis of mouse spleen cells revealed proinflammatory macrophages express the highest levels of IL-6Rα, and in vitro treatment with IL-6 blocked macrophage proliferation. Furthermore, proinflammatory macrophages were expanded during inflammation in IL-6(-/-) mice. Late application of anti-IL-6 after establishment of adaptive nephritogenic immunity was sufficient to aggravate NTN within 2.5 days, a period when macrophages are active. Finally, NTN was aggravated in mice with macrophage-specific impairment of IL-6 classic signaling, coincident with enhanced macrophage proliferation and accumulation in the kidney. Our data thus reveal a novel mechanism in which IL-6-mediated dampening of macrophage activation protects tissues from overshooting immune responses. This finding has important implications for potential IL-6-directed therapies and supports the careful choice of recipient patients and timing.

Glomerular inflammation correlates with endothelial injury and with IL-6 and IL-1β secretion in the peripheral blood

BACKGROUND

Transplant glomerulitis is an active form of glomerular injury associated with suboptimal graft outcome, inadequate histologic reproducibility, and poorly understood pathogenesis. Using a modified pathologic schema where glomerular inflammation is defined by the presence of five or more leukocytes per glomerulus, we sought to assess the reproducibility of transplant glomerulitis and to prospectively investigate the pathogenesis of glomerular inflammation.

METHODS

Our cohort includes 59 kidney transplant recipients who underwent 60 "for cause" allograft biopsies. In addition to light microscopy, the majority of the biopsies were assessed using immunohistochemistry, immunofluorescence, and electron microscopy studies. Biopsies were classified as noninflamed (n=21), inflamed (borderline changes or above) without glomerulitis (n=21), and transplant glomerulitis (n=18). Peripheral blood was collected on the day of biopsy and cytokines secreted by peripheral blood mononuclear cells (PBMCs) were measured ex vivo.

RESULTS

Our modified schema had higher inter-observer agreement for detecting glomerulitis than that of the current Banff schema. Biopsies with glomerulitis showed ultrastructural signs of glomerular capillary wall remodeling. In contrast to other anatomic compartments, intraglomerular leukocytes in glomerulitis group consisted largely of monocytes. Patients with glomerulitis had high levels of IL-6 and IL-1β secreted by PBMCs. Furthermore, the percentage of inflamed glomeruli and the number of intraglomerular monocytes showed independent association with IL-6 and IL-1β levels, which tended to correlate with subsequent estimated glomerular filtration rate decline.

CONCLUSIONS

Inter-observer reproducibility of transplant glomerulitis can be improved by using more stringent histologic criteria. Glomerular inflammation correlates with endothelial injury, monocyte influx, and IL-6 and IL-β secretion by circulating immune cells.

Prolonged renal allograft survival by donor interleukin-6 deficiency: association with decreased alloantibodies and increased intragraft T regulatory cells

Both humoral and cellular immune responses are involved in renal allograft rejection. Interleukin (IL)-6 is a regulatory cytokine for both B and Foxp3 (forkhead box P3)-expressing regulatory T (Treg) cells. This study was designed to investigate the impact of donor IL-6 production on renal allograft survival. Donor kidneys from IL-6 knockout (KO) vs. wild-type (WT) C57BL/6 mice (H-2b) were orthotopically transplanted to nephrotomized BALB/c mice (H-2d). Alloantibodies and Treg cells were examined by fluorescence-activated cell sorting analysis. Graft survival was determined by the time to graft failure. Here, we showed that a deficiency in IL-6 expression in donor kidneys significantly prolonged renal allograft survival compared with WT controls. IL-6 protein was upregulated in renal tubules and endothelium of renal allografts following rejection, which correlated with an increase in serum IL-6 compared with that in those receiving KO grafts or naive controls. The absence of graft-producing IL-6 or lower levels of serum IL-6 in the recipients receiving IL-6 KO allografts was associated with decreased circulating anti-graft alloantibodies and increased the percentage of intragraft CD4+CD25+Foxp3+ Treg cells compared with those with WT allografts. In conclusion, the lack of graft-producing IL-6 significantly prolongs renal allograft survival, which is associated with reduced alloantibody production and/or increased intragraft Treg cell population, implying that targeting donor IL-6 may effectively prevent both humoral and cellular rejection of kidney transplants.

Inflammation-associated graft loss in renal transplant recipients

BACKGROUND

Although short-term graft survival has improved substantially in renal transplant recipients, long-term graft survival has not improved over the last decades. The lack of knowledge of specific causes and risk factors has hampered improvements in long-term allograft survival. There is an uncertainty if inflammation is associated with late graft loss.

METHODS

We examined, in a large prospective trial, the inflammation markers high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) and their association with chronic graft dysfunction. We collected data from the Assessment of Lescol in Renal Transplant trial, which recruited 2102 maintenance renal transplant recipients.

RESULTS

Baseline values were hsCRP 3.8 ± 6.7 mg/L and IL-6 2.9 ± 1.9 pg/mL. Adjusted for traditional risk factors, hsCRP and IL-6 were independently associated with death-censored graft loss, the composite end points graft loss or death and doubling of serum creatinine, graft loss or death.

CONCLUSION

The inflammation markers hsCRP and IL-6 are associated with long-term graft outcomes in renal transplant recipients.

Urinary proinflammatory cytokine response in renal transplant recipients with polyomavirus BK viruria

BACKGROUND

Polyomavirus BK (BKV) has emerged as an important complication after kidney transplantation. BKV-associated nephropathy develops in approximately 5% to 8% of renal transplant recipients, and its prognosis is poor. The relationship between urine cytokines and BK viruria in kidney recipients has not been defined.

PATIENTS AND METHODS

We compared posttransplant urine cytokine levels of 65 renal transplant outpatients with (BK-positive) or without BK viruria (BK-negative, n=33), low- (n=16) or high-level (n=16) BK viral load (VL), and 24 healthy controls (HCs). Soluble interleukin-1 receptor antagonist (sIL-1RA), interleukin (IL)-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, IL-17, transforming growth factor-beta2, interferon-gamma, and tumor necrosis factor-alpha levels were determined using commercially available ELISA kits.

RESULTS

BK-positive patients showed higher urine IL-3 (P=0.006), sIL-6R (P=0.010), IL-6 (P=0.020), and sIL-1RA (P=0.050) than BK-negative patients. Compared with HCs, BK-negative patients had lower urine sIL-1RA (P=0.003), sIL-6R (P=0.001), and IL-17 (P<0.001), whereas BK-positive patients had higher urine IL-3 (P=0.004) and IL-6 (P=0.001) and lower IL-17 (P<0.001), suggesting cytokine suppression by immunosuppression and upregulation by BK-infection. Urine sIL-6R (P=0.003) and IL-6 (P=0.010) were higher in patients with high VL than in patients with low VL. Additionally, patients with high VL showed higher urine IL-6 (P=0.001), sIL-6R (P=0.001), sIL-1RA (P=0.016), and IL-3 (P=0.047) than BK-negative patients, and higher urine IL-6 (P<0.001) and lower IL-17 (P<0.001) than HCs.

CONCLUSION

BK-positive renal transplant recipients, especially those with high VL, showed strong inflammatory cytokine responses with increases of urine sIL-1RA, IL-3, IL-6, and sIL-6R. Our data suggest that monocyte- and Th-2-induced cytokines are involved in the pathogenesis of BKV-associated nephropathy.

Effect of amnion derived stem cells on inflammatory response in endotoxemic rats

BACKGROUND

Systemic inflammatory response syndrome (SIRS) and sepsis are one among the most common causes of death in intensive care units. Tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-10 (IL-10) increase during SIRS and sepsis. Recent studies have demonstrated that amnion derived stem cells have anti-inflammatory effects, low immunogenicity and pluripotency. In addition, there is little ethical objection to the use of amnion derived stem cells. Here, the author presents the first study demonstrating the therapeutic potential for the use of amnion derived stem cells in a rat model of SIRS and sepsis.

METHODS

Amnion derived stem cells were isolated from amnion obtained from an uncomplicated Cesarean section and cultured. SIRS and sepsis were induced in rats by lipopolysacchride (15 mg/kg, LPS), and amnion derived stem cells were then transplanted intravenously. The heart rate, mean arterial pressure and the concentration of TNF-alpha, IL-6 and IL-10 were assessed at baseline and 2 hours and 4 hours after procedure.

RESULTS

The changes of heart rate and mean arterial pressure were reduced in the amnion derived stem cells transplanted group. In addition, increases in the plasma concentration of TNF-alpha, IL-6 and IL-10 were attenuated in the amnion derived stem cells transplanted group.

CONCLUSIONS

This study demonstrated that amnion derived stem cells attenuate inflammatory response during SIRS and sepsis. Transplantation of amnion derived stem cells can be a novel cell based therapeutic strategy for SIRS and sepsis.

IL-2, IL-6 and IL-8 levels remain unaltered in the course of immunosuppressive therapy after renal transplantation

Cytokines regulate the immune reactions elicited by renal transplantation (RT). This study was designed to investigate the blood serum levels of IL-2, IL-6, IL-8 in 25 RT patients (10 female and 15 male, mean 5.4±2.7 yrs after RT) three times over a six-month period during standard immunosuppressive therapy with cyclosporine A, azathioprine and prednisolone. The levels of IL-2, IL-6 and IL-8 were tested with ELISA Quantikine Human Interleukin Immunoassay (R&D Systems, detection level 7,0.7 and 10 pg/cm3, respectively). There was no significant alternation of blood serum levels of IL-2, IL-6 and IL-8 in the study patients.

Renal transplant rejection markers

Acute rejection is one of the key factors which determine long-term graft function and survival in renal transplant patients. Timely detection and treatment of rejection is therefore, an important goal in the post-transplant surveillance. The standard care with serum creatinine measurements and biopsy upon allograft dysfunction implies that acute rejection is detected in an advanced stage. Therefore, non-invasive monitoring for acute rejection by markers in blood and urine has been tried over the past decades. This review describes the requirements that should be met by non-invasive markers. The experience with single biomarkers and with newer approaches--mRNA expression analysis, metabolomics, and proteomics--will be discussed, including future directions of necessary research.

Renal Allograft Immune Response Is Influenced by Patient and Donor Cytokine Genotypes

This study investigated the impact of specific cytokine genotypes on the incidence of acute rejection episodes (ARE), chronic graft dysfunction (CGD), and anti-HLA donor-specific antibody (DS-Ab) production in 86 renal transplant recipients and 70 cadaveric donors. A PCR-SSP method was performed for the analysis of polymorphisms in TNF-alpha, IL-6, TGF-beta, IL-10, and IFN-gamma cytokines. DS-Ab monitoring of sera was performed using a FCXM analysis. Observed cytokine frequencies for patients and donors were not significantly different from the expected frequencies under Hardy-Weinberg equilibrium conditions. The evaluation in recipients revealed a higher frequency of DS-Ab-positive patients among the TNF-alpha high (50.0% vs 25.7%), and for the IL-10 cytokine a greater incidence of ARE-positive patients (35.8% vs 18.2%) with the high + intermediate, compared with the low genotype. The combined effect of these 2 genotypes predisposed to DS-Abs (71.4% vs 25.3%; P = 0.02; odds ratio [OR] = 7.37). As for the TGF-beta1 cytokine, we observed a higher number of CGD-positive patients among high compared with intermediate producers (14.3% vs 0%; P = .050). The analysis of donors revealed a significantly lower incidence of ARE-positive patients among recipients whose donors were carriers of the high IL-6 G/G-genotype compared with the G/C+C/C-genotypes (16.7% vs 41.2%; P = .03), suggesting a protective effect of the G/G genotype on ARE and a predisposing role of donor (-174)allele C. In addition, we noted an association between the IFN-gamma low A/A-genotype and a higher incidence of ARE (42.1% vs 0%; P = .002) and DS-Ab production (47.4% vs 12.5%; P = .02) compared with high producers.

Diagnostic Tools for Monitoring Kidney Transplant Recipients

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

Interleukin-6 stimulates alpha-MG uptake in renal proximal tubule cells: involvement of STAT3, PI3K/Akt, MAPKs, and NF-kappaB

Recent studies have shown that interleukin 6 (IL-6) acts on the cellular proliferation-activating transduction signals during cellular regeneration. Therefore, this study examined the effect of IL-6 on the activation of Na(+)/glucose cotransporters (SGLTs) and its related signaling pathways in primary cultured renal proximal tubule cells (PTCs). IL-6 increased the level of alpha-methyl-d-[(14)C]glucopyranoside (alpha-MG) uptake in time- and dose-dependent manners. IL-6 also increased SGLT1 plus SGLT2 mRNA and protein expression level. The IL-6 receptors (IL-6Ralpha and gp 130) were expressed in PTCs. In addition, genistein and herbimycin A completely blocked the IL-6-induced increases in alpha-MG uptake and the protein expression level of SGLTs. On the other hand, IL-6 increased the level of 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate-sensitive cellular reactive oxygen species (ROS), and IL-6-induced increases in alpha-MG uptake and the protein expression level of SGLTs were blocked by ascorbic acid or taurine (antioxidants). IL-6 also increased the phosphorylation of signal transducer and activator of transcription-3 (STAT3), phosphoinositide-3 kinase (PI3K)/Akt, and mitogen-activated protein kinases (MAPKs) in a time-dependent manner. A pretreatment with STAT3 inhibitor LY 294002, an Akt inhibitor, or MAPK inhibitors significantly blocked the IL-6-induced increase in alpha-MG uptake. In addition, IL-6 increased the level of nuclear factor-kappaB (NF-kappaB) phosphorylation. A pretreatment with SN50 or BAY 11-7082 also blocked the IL-6-induced increase in alpha-MG uptake. In conclusion, IL-6 increases the SGLT activity through ROS, and its action in renal PTCs is associated with the STAT3, PI3K/Akt, MAPKs, and NF-kappaB signaling pathways.

Characterization of urinary peptide biomarkers of acute rejection in renal allografts

We previously demonstrated that 4.7 kDa and 4.4 kDa peptides are useful in diagnosing acute rejection in renal transplant recipients. The aim of this study was to characterize these polypeptides and assess their potential as biomarkers. The polypeptides were identified as human beta-Defensin-1 (4.7 kDa) and alpha-1-antichymotrypsin (4.4 kDa), by tandem mass spectrometry and ProteinChip immunoassay. The urinary abundance of both polypeptides, assessed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), revealed a reduction in beta-Defensin-1 while alpha-1-antichymotrypsin increased in patients with rejection (p < 0.05) compared with clinically stable transplants. The area under the curve (AUC) for the receiver operator characteristic (ROC) curve for the diagnosis of rejection for the ratio of both peptides combined was 0.912. Longitudinal analysis confirmed a reduction in beta-Defensin-1 with a reciprocal increase in alpha-1-antichymotrypsin as rejection developed. The difference in urinary beta-Defensin-1 levels quantified by radioimmunoassay was 176.8 +/- 122.3 pg/mL in stable patients compared with 83.2 +/- 52.2 pg/mL in patients with acute rejection, with an ROC AUC of 0.749 (p < 0.01). Immunohistochemistry (IHC) confirmed reduced beta-Defensin-1 expression in the renal parenchyma of patients experiencing acute rejection. In conclusion, the ratio of beta-Defensin-1 and alpha-1-antichymotrypsin excretion in the urine is a novel, potentially useful candidate biomarkers of acute rejection.

Reticulocytes and their immature fraction do not detect acute rejection after kidney transplantation

BACKGROUND

Early detection of an acute rejection episode is an important problem in monitoring transplant patients. Erythropoietin (EPO) production is diminished in patients suffering from chronic renal insufficiency or acute rejection. Therefore, a decrease of reticulocyte counts and of young reticulocytes might indicate the emergence of an acute rejection episode. This pilot study examined the value of reticulocyte parameters as indicators of acute rejection episodes.

PATIENTS AND METHODS

Reticulocyte parameters were examined in 25 renal transplant patients. Initial immunosuppressants therapy was based on a combination of methylprednisolone, mycophenolatmofetil, cyclosporine and antithymocyte globulin or basiliximab, CellCept, cyclosporine, and ATG or Simulect. During the first 3 weeks after the procedure, blood samples were collected three times per week. Complete blood counts were performed on XE-2100 analyzers (Sysmex). Acute rejection was biopsy-proven.

RESULTS

Acute rejection episodes were not accompanied by significantly altered reticulocyte parameters. During the first weeks, the reticulocyte count or the immature fraction, respectively, did not differ between patients with delayed versus immediate onset of renal function: reticulocyte count 1.70 +/- 1.06% vs 1.58 +/- 1.10% and ratio of immature (high fluorescent) reticulocytes 22.8 +/- 7.9% vs 17.6 +/- 9.4%).

CONCLUSION

Reticulocyte counts and determination of the immature reticulocyte fraction were not significantly altered by an acute rejection episode. Various influences modulate the release of EPO and reaction of erythropoiesis upon an EPO stimulus.

Validation of Immunological Biomarkers for the Pharmacodynamic Monitoring of Immunosuppressive Drugs in Humans

Pharmacodynamic monitoring (PD) can evaluate the efficacy of immunosuppressive drug therapies. In this study, the expressions of PD biomarkers [lymphocyte proliferation, CD25 and CD71 expression, interleukin-2 (IL-2), and tumor necrosis factor-alpha (TNF-alpha) synthesis] were determined in whole-blood assays and were validated for their application in PD of immune modulators in future clinical trials. Initially, the assay conditions were re-evaluated. The measurement of T-lymphocyte proliferation and activation marker expression in whole-blood cultures resulted in optimized stimulation for 72 hours with 7.5 microg/mL concavalin A. Intracellular cytokine expression of CD3+ T-cells received optimized stimulation for 4 hours with 15 ng/mL phorbol 12-myristate 13-acetate and 0.75 microg/mL ionomycin. Statistical assay parameters (intra-assay, intra-individual, and interindividual variabilities) were determined. It was found that blood storage for up to 24 hours is possible without any change in biomarker expression. Dosage effects of immunosuppressive drugs (tacrolimus, cyclosporin A, sirolimus, mycophenolic acid, and methylprednisolone) were evaluated in vitro and the assay was applied successfully to dialysis, renal transplant, and liver transplant patients. We conclude that these biomarkers used in whole-blood assays are suitable for PD of immune modulators in clinical trials.

Elevated serum interleukin-6 (IL-6) in solid-organ transplant recipients is positively associated with tissue destruction and IL-6 gene expression in the periodontium

BACKGROUND

The number of transplanted solid organs and life expectancy after transplantation are steadily rising worldwide. Inflammation is widely recognized as playing a pivotal role in transplant rejection, and several studies have shown that serum interleukin-6 (IL-6) levels can identify individuals who are at greater risk for rejection. Given the known association between IL-6 and chronic periodontitis, the aim of our study was to assess the periodontal status of solid-organ transplant subjects compared to systemically healthy controls, to quantify the IL-6 levels in the serum and periodontal tissues, and to explore their association.

METHODS

Forty-seven heart and kidney transplant and 18 systemically healthy age-matched individuals were recruited. Subjects received a complete periodontal examination, and blood and periodontal tissue samples were collected for quantification of IL-6 protein and mRNA levels, respectively.

RESULTS

Transplant subjects had significantly higher serum IL-6 levels and slightly but statistically significantly increased mean probing depths than healthy controls. Multivariable linear regression analysis adjusting for gender, diabetes, smoking, and immunosuppressant dose showed that the mean probing depth, number of missing teeth, and mean percentage of sites with > or =4 mm attachment loss were independent predictors for elevated serum IL-6 levels. Transplant subjects with chronic periodontitis had higher mean serum IL-6 levels than those without chronic periodontitis, and there was a positive correlation between periodontal IL-6 gene expression levels and serum IL-6 protein levels.

CONCLUSIONS

Periodontal tissue destruction and local IL-6 synthesis are associated with elevated serum IL-6 levels in transplant recipients. This may have serious implications in solid-organ transplant deterioration and chronic rejection.

Beyond histology: novel tools to diagnose allograft dysfunction

Kidney biopsy is the gold standard procedure for the assessment of allograft dysfunction. The differential diagnosis for both acute and chronic dysfunction can encompass a number of different causes, and a biopsy frequently can suggest a specific cause. However, many of these causes are difficult to distinguish on morphologic basis alone, and the information that is obtained from a biopsy is limited with regard to functional and prognostic importance. Additional methods therefore are needed to guide the diagnosis and the treatment of allograft dysfunction, and numerous methods have been studied. Potential markers include protein and gene expression profiles in the peripheral blood, the urine, and the graft itself, all compartments that are relevant to the alloimmune response. Recent comprehensive sequencing of the human genome has led to an unprecedented opportunity to develop these genetic and proteomic techniques, and ongoing evaluations of potential tests have led to an improved understanding of the complexity of immune responses. The future challenge for promising tests is validation in larger patient populations to facilitate their addition to the diagnostic armamentarium.

Markers of Inflammation Before and After Renal Transplantation

BACKGROUND

This study aims to compare serum C-reactive protein (CRP), interleukin (IL-6), and tumor necrosis factor (TNF)-alpha in end-stage renal disease (ESRD) patients before versus after receiving renal transplantation (RT) and versus donors.

METHODS

Serum samples from 37 ESRD patients (24 male, age 34+/-13 years) were collected before and after RT; in addition, samples from 31 donors were obtained at transplantation. CRP concentrations were measured using nephelometry, and TNF-alpha and IL-6 were measured by enzyme-linked immunoadsorbent assay.

RESULTS

Ninety-two percent of recipients had a living donor, 73% received cyclosporine A, 27% tacrolimus, and 70% induction with daclizumab. Thirteen percent had acute rejection and 16% chronic allograft nephropathy. All inflammation markers decreased 6 months after RT, but only CRP was below baseline values (baseline: 5.0+/-3.5; 6 months: 3.0+/-0; 12 months: 3.2+/-0.7; 18 months: 3.2+/-0.6; donors: 3.6+/-1.5 mg/L; P<0.05), whereas median TNF-alpha (baseline: 0.1 [0.03-0.2]; 6 months: 0 [0-0.1]; 12 months: 0.3 [0.1-2.6]; 18 months: 0.6 [0.1-1.9]; donors: 0 [0-0.1] pg/mL; P<0.05) and IL-6 (baseline: 1.9 [1.2-7.1]; 6 months: 1.2 [0.6-28.3]; 12 months: 2.6 [1.3-3.4]; 18 months: 2.7 [1.7-4.2]; donors: 1.1 [0.6-1.9] pg/mL; P<0.05) significantly increased up to the end of follow-up. Before RT, CRP correlated with age (r 0.45, P=0.006) and albumin (r -0.36, P=0.04). TNF-alpha and IL-6 were correlated before (r 0.34, P=0.04) and after (r 0.55, P=0.02) RT. Inflammation markers were not different in patients who had acute rejection episodes or chronic nephropathy.

CONCLUSIONS

Compared with controls, patients displayed an inflammatory phenomenon before receiving RT. Serum CRP decreased significantly after RT, whereas TNFalpha and IL-6 increased.

Biologic markers for the early detection of acute kidney injury

PURPOSE OF REVIEW

This review discusses the current status of several biomarkers as potential diagnostic tools in patients with acute kidney disease.

RECENT FINDINGS

Although the term "acute renal failure" has generally been used to describe acute kidney dysfunction that runs the spectrum from mild prerenal azotemia with no renal pathologic changes and no functional failure to severe oliguric renal dysfunction associated with tubular necrosis with failure of function, this spectrum is better described by the term "acute kidney injury." The mortality rate of hospitalized patients with severe acute kidney disease has not decreased significantly over the past 50 years despite advances in supportive care. The absence of sensitive and specific biomarkers for detecting injury early, grading the severity of the injury, and monitoring the response to therapy has impaired progress in the field and has had a very detrimental effect on the design and outcome of clinical trials in acute kidney disease. As a result of reliance on serum creatinine as a marker for injury and diagnosis, the institution of therapy is markedly delayed.

SUMMARY

The search for new biomarkers for acute kidney injury is evolving rapidly with advancement in modern technologies. With better biomarkers we will have the ability to detect injury earlier, identify subclinical injury, provide prognostic information on the course of renal impairment, identify the nephron segments most affected, provide a rationale for segmentation of patients for clinical studies, guide timing of therapy, assess response to therapy, and screen patients at risk for renal injury.

Risk factors for cardiovascular disease in pediatric renal transplant recipients

About 1,000 children develop end-stage renal disease (ESRD) each year in the United States and about 5,000 children are currently receiving dialysis. Children who develop ESRD are eligible to receive renal replacement therapy, including renal transplantation. There are inherent risks associated with transplantation, including renal insufficiency, infections, post-transplant lymphoproliferative disorder, and cardiovascular disease (CVD). Potential risk factors for CVD in pediatric renal transplant recipients include renal insufficiency, hyperlipidemia, hyperhomocysteinemia, inflammation, malnutrition, anemia, and hyperglycemia/insulin resistance. Despite evidence that many children may possess various risk factors for CVD post-renal transplantation, there are very few studies that have attempted to assess the link between these risk factors and CVD in pediatric renal transplant recipients.

High urine sIL-6R as a predictor of late graft failure in renal transplant recipients

BACKGROUND

Chronic allograft nephropathy is an important cause of late renal transplant failure. Although numerous studies on cytokines have been carried out, the pathogenetic role of cytokines in chronic renal allograft nephropathy remains unclear.

METHODS

In a retrospective study, the authors compared posttransplant plasma and urine cytokine levels (interleukin [IL]-1alpha, IL-1beta, soluble [s] IL-1 receptor [R] antagonist [A], IL-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, tumor necrosis factor-alpha, transforming growth factor-beta2, and interferon-gamma) in 34 matched pairs of patients with or without late graft failure and in 50 matched pairs with either normal or increased serum creatinine levels and continued stable graft function.

RESULTS

Twelve and 6 months before late graft failure, urine levels of sIL-6R were significantly increased (P=0.003 and P=0.01, respectively). Serum creatinine levels were not associated with increased urine sIL-6R.

CONCLUSION

High urine sIL-6R appears to be predictive of late graft failure in renal transplant recipients.

Gammadelta T cells and interleukin-6 levels could provide information regarding the progression of human renal allograft

We have determined the percentage of alphabeta and gammadelta T cells by flow cytometry as well as serum interleukin-6 (IL-6) and soluble interleukin-6 receptor (sIL-6R) levels by enzyme-linked immunosorbent assay in kidney allograft recipients with acute, chronic or stable graft evolution. The percentage of CD4 and CD8 T cells in transplanted patients was lower than in the control group (P < 0.001) with the exception of CD8 gammadelta T cells from patients with stable evolution (P > 0.05). The serum levels of IL-6 and sIL-6R in acute and chronic rejection were higher than in the controls (P < 0.05). No differences in IL-6 levels were observed between the stable evolution and the control groups (P > 0.05). The levels of sIL-6R were higher in stable evolution patients than in the controls (P < 0.05) and no differences were observed between the chronic and stable evolution patients (P > 0.05). IL-6 decreased in patients with a favourable evolution, increased in those with an increased renal dysfunction and was maintained when the renal dysfunction was not modified. These results suggest that gammadelta T cells could participate in renal allograft maintenance and that IL-6 but not sIL-6R serum levels may provide a prognostic marker for measuring the evolution of kidney allograft.

Urinary actin, interleukin-6, and interleukin-8 may predict sustained ARF after ischemic injury in renal allografts

BACKGROUND

Cellular damage and inflammation after ischemia contribute to sustained acute renal failure (ARF).

METHODS

To quantify cellular damage and inflammation in postischemic ARF and identify markers of renal functional outcome, urine specimens from 40 renal allograft recipients, including 30 cadaveric (9 "sustained ARF" and 21 "recovery" subjects) and 10 living donor allografts ("LD"), were analyzed for actin, gamma-glutamyl transpeptidase (GGTP), lactate dehydrogenase (LDH), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) during the first posttransplant week.

RESULTS

On day 0, urinary actin, GGTP, IL-6, and IL-8 were elevated in recipients destined to have sustained ARF compared with those destined to recover. Median values per gram of urine creatinine in the sustained ARF, recovery, and LD groups were 263.9, 0.0, and 0.0 microg for actin; 5000.0, 892.9, and 5555.6 U for GGTP; 193.1, 27.2, and 10.5 ng for IL-6; and 382.0, 17.8, and 18.5 ng for IL-8, respectively. In contrast, urinary LDH and TNF-alpha increased in recipients with recovering function compared with those who had sustained ARF. The corresponding median values were 36.7 and 16.3 U (recovery versus sustained ARF) for LDH, and 18.4 and 7.6 ng (LD versus sustained ARF) for TNF-alpha. Computational analyses using the Receiver Operating Characteristic Curve found that elevated urinary actin, IL-6, and IL-8 on day 0 were strong predictors of sustained ARF, where the calculated areas under the curve were 0.75, 0.91, and 0.82, respectively.

CONCLUSION

Increased urinary actin, IL-6, and IL-8 may be useful markers for the prediction of sustained ARF after ischemia.

Increasing transplant mass results in long-term allograft survival and recovery from transplant vasculopathy

Late allograft rejection due to transplant vasculopathy continues to be a major clinical problem. Increasing the ratio of donor transplant size to recipient weight has been shown to reduce the incidence of late allograft failure. Using a murine pancreas transplant model we have tested the hypothesis that increasing the donor transplant size in a recipient can promote long-term allograft survival by promoting recovery from transplant vasculopathy. Recipients of an allograft that showed extensive vasculopathy were transplanted with a second donor transplant. The effect of the second allograft on the vasculopathy present in the first graft was measured. Transplanting a second allograft reversed all signs of ongoing rejection, including transplant vasculopathy, resulting in long-term survival of the first graft. Vasculopathy was only reversed if the first and second grafts were from the same mouse strain, suggesting an antigen-specific mechanism. However, the recovery of the first graft was not associated with antigen-specific peripheral tolerance.

Genetic polymorphisms influencing therapy and susceptibility to rejection in organ allograft recipients

Solid organ transplantation during the past 30 years has developed from an experimental procedure into routine clinical practice. The current repertoire of immunosuppressive agents has made a major contribution to transplant survival; however, problems in different areas still need to be overcome. Several gene polymorphisms are supposed to influence immunosuppressive therapy and susceptibility to rejection. Therefore, a priority of transplant biologists is to estimate individual patient risk and to characterise the genetic profile of patients in need of a transplant in order to optimise the use of a scarce resource such as organs from cadaver donors, and to avoid serious drug-induced adverse effects. Polymorphisms in genes encoding tumour necrosis factor-alpha (TNFalpha), interleukin (IL)-6, IL-10, interferon-gamma (IFNgamma), transforming growth factor-beta (TGFbeta) and thiopurine S-methyltransferase (TPMT) can have significant effects on an individual's risk of rejection, as well as their ability to tolerate immunosuppressive therapy. Genotyping of known polymorphisms in these genes may in the future contribute to our ability to individualise immunosuppressive therapy in organ transplant recipients.