Chemokines: directing leukocyte infiltration into allografts

Urine CXCL10 as a biomarker in kidney transplantation

PURPOSE OF REVIEW

Urine CXCL10 is a promising biomarker for posttransplant renal allograft monitoring but is currently not widely used for clinical management.

RECENT FINDINGS

Large retrospective studies and data from a prospective randomized trial as well as a prospective cohort study demonstrate that low urine CXCL10 levels are associated with a low risk of rejection and can exclude BK polyomavirus replication with high certainty. Urine CXCL10 can either be used as part of a multiparameter based risk assessment tool, or as an individual biomarker taking relevant confounders into account. A novel Luminex-based CXCL10 assay has been validated in a multicenter study, and proved to be robust, reproducible, and accurate.

SUMMARY

Urine CXCL10 is a well characterized inflammation biomarker, which can be used to guide performance of surveillance biopsies. Wide implementation into clinical practice depends on the availability of inexpensive, thoroughly validated assays with approval from regulatory authorities.

CD14highCD16+ monocytes are the main producers of Interleukin-10 following clinical heart transplantation

Introduction

Following heart transplantation, a cascade of immunological responses is initiated influencing the clinical outcome and long-term survival of the transplanted patients. The anti-inflammatory cytokine interleukin-10 (IL-10) was shown to be elevated in the blood of heart transplant recipients directly after transplantation but the releasing cell populations and the composition of lymphocyte subsets following transplantation have not been thoroughly studied.

Methods

We identified immune cells by immunophenotyping and analyzed intracellular IL-10 production in peripheral blood mononuclear cells (PBMC) of heart transplanted patients (n= 17) before, directly after and 24h post heart transplantation. The cells were stimulated with lipopolysaccharide or PMA/Ionomycin to enhance cytokine production within leukocytes in vitro.

Results and discussion

We demonstrate that intermediate monocytes (CD14highCD16+), but not CD8+ T cells, CD4+ T cells, CD56+ NK cells or CD20+ B cells appeared to be the major IL-10 producers within patients PBMC following heart transplantation. Consequently, the absolute monocyte count and the ratio of intermediate monocytes to classical monocytes (CD14+CD16-) were specifically increased in comparison to pre transplant levels. Hence, this population of monocytes, which has not been in the focus of heart transplantation so far, may be an important modulator of clinical outcome and long-term survival of heart transplant recipients. Alteration of blood-circulating monocytes towards a CD14highCD16+ phenotype could therefore shift the pro-inflammatory immune response towards induction of graft tolerance, and may pave the way for the optimization of immunosuppression.

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

SIGNIFICANCE STATEMENT

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Immediate major dynamic changes in the T- and NK-cell subset composition after cardiac transplantation

Early kinetics of lymphocyte subsets involved in tolerance and rejection following heart transplantation (HTx) are barely defined. Here, we aimed to delineate the early alloimmune response immediately after HTx. Therefore, blood samples from 23 heart-transplanted patients were collected before (pre-), immediately (T0), 24 hours (T24), and 3 weeks (3 wks) after HTx. Immunophenotyping was performed using flow cytometry. A significant increase was detected for terminally differentiated (TEMRA) CD4+ or CD8+ T cells and CD56dim CD16+ NK cells immediately after HTx linked to a decrease in naïve CD8+ and CM CD4+ T as well as CD56bright CD16- NK cells, returning to baseline levels at T24. More detailed analyses revealed increased CD69+ CD25- and diminished CD69- CD25- CD4+ or CD8+ T-cell proportions at T0 associated with decreasing S1PR1 expression. Passenger T and NK cells were found at low frequencies only in several patients at T0 and did not correlate with lymphocyte alterations. Collectively, these results suggest an immediate, transient shift toward memory T and NK cells following HTx. Opposite migratory properties of naïve versus memory T and NK cells occurring in the early phase after HTx could underlie these observations and may impinge on the development of allo-specific immune responses.

Lymphocytic Airway Inflammation in Lung Allografts

Lung transplant remains a key therapeutic option for patients with end stage lung disease but short- and long-term survival lag other solid organ transplants. Early ischemia-reperfusion injury in the form of primary graft dysfunction (PGD) and acute cellular rejection are risk factors for chronic lung allograft dysfunction (CLAD), a syndrome of airway and parenchymal fibrosis that is the major barrier to long term survival. An increasing body of research suggests lymphocytic airway inflammation plays a significant role in these important clinical syndromes. Cytotoxic T cells are observed in airway rejection, and transcriptional analysis of airways reveal common cytotoxic gene patterns across solid organ transplant rejection. Natural killer (NK) cells have also been implicated in the early allograft damage response to PGD, acute rejection, cytomegalovirus, and CLAD. This review will examine the roles of lymphocytic airway inflammation across the lifespan of the allograft, including: 1) The contribution of innate lymphocytes to PGD and the impact of PGD on the adaptive immune response. 2) Acute cellular rejection pathologies and the limitations in identifying airway inflammation by transbronchial biopsy. 3) Potentiators of airway inflammation and heterologous immunity, such as respiratory infections, aspiration, and the airway microbiome. 4) Airway contributions to CLAD pathogenesis, including epithelial to mesenchymal transition (EMT), club cell loss, and the evolution from constrictive bronchiolitis to parenchymal fibrosis. 5) Protective mechanisms of fibrosis involving regulatory T cells. In summary, this review will examine our current understanding of the complex interplay between the transplanted airway epithelium, lymphocytic airway infiltration, and rejection pathologies.

Mechanisms underlying the production of chemokine CXCL11 in the reaction of renal tubular epithelial cells with CD4+ and CD8+ T cells

AIM

To study the release mechanism of C-X-C motif chemokine 11 (CXCL11) and other chemokines after the co-cultivation of CD4⁺ and CD8⁺ T cells with the renal tubular epithelial cells (RTEC) in the process of allograft renal transplantation rejection.

METHODS

The Human CD4⁺, CD8⁺ T cells were obtained from the blood of volunteers and kidney transplantation (Ktx) patients, and co-cultured with renal tubular epithelial cells (RTEC) in vitro. RT-PCR was run for detecting the mRNA transcription of CXCL11, IFN-induced protein of 10 (CXCL10), and IL-6 in cells after RTEC was stimulated with IFN-γ or co-cultured with CD4⁺ and CD8⁺ T cells. The concentration of CXCL11, CXCL10 and IL-6 in the culture medium was detected by Multiplex Assay after RTEC was stimulated with IFN-γ or co-cultured with CD4⁺ and CD8⁺ T cells. IFN-γ receptor antibody was used for interfering with the above reaction and the blocking effect was observed. Western blot was used for protein expression analysis. Finally, we applied renal biopsies from kidney transplantation patients with and without rejection to verify the results of the above experiments by using RT-PCR and Western blot.

RESULTS

The mRNA expression of CXCL11 and CXCL10 were significantly increased after RTEC was stimulated with IFN-γ or co-cultured with CD4⁺ and CD8⁺ T cells. Multiplex Assay showed that the concentration of CXCL11 and CXCL10 in the supernatant were significantly increased in a time-dependence fashion after stimulation RTEC by IFN-γ. Anti-IFN-γ receptor1 (anti-IFN-γR1) antibody could reduce the production of CXCL11 and CXCL10 in this situation. The concentration of CXCL11 and CXCL11 in the supernatant was significantly increased with a time-dependent effect after the co-culture of CD4⁺ and CD8⁺ T cells with RTEC. The anti-IFN-γR1 blocked this effect. Our study showed that the expression levels of CXCL11 and CXCL10 were upgraded in the biopsies of patients with renal transplant rejection comparatively to pre-transplant biopsies, both at mRNA and protein levels.

CONCLUSIONS

RTEC and T cells can stimulate each other during the acute rejection of allogeneic kidney transplantation and secret CXCL11，CXCL10 and other chemokines. IFN-γ plays a key role in this process.

Technical Considerations and Confounders for Urine CXCL10 Chemokine Measurement

Background.

The urine C-X-C motif chemokine 10 (CXCL10) is a promising screening biomarker for renal allograft rejection. The aim of the study was to investigate important technical and biological aspects as well as potential confounders when measuring urine CXCL10.

Methods.

We analyzed 595 urine samples from 117 patients, who participated in a randomized controlled trial investigating the clinical utility of urine CXCL10 monitoring for posttransplant management. Urine CXCL10 was measured by an immunoassay using electrochemiluminescence.

Results.

Intraassay coefficient of variation was 2.5%, and interassay coefficient of variation was 10%. Urine CXCL10 remained stable (ie, <10% degradation) for 8 hours at 25°C or 37°C and for 3 days at 4°C. CXCL10 concentrations [pg/mL] strongly correlated with urine CXCL10/creatinine ratios [ng/mmol] (r² = 0.98; P < 0.0001). Leucocyturia and active BK-polyomavirus infection are associated with higher CXCL10 concentrations, while allograft function, serum CRP, patient age, proteinuria, urine pH, hematuria, squamous epithelia cell count, and bacteriuria did not correlate with urine CXCL10 concentrations. In 145 paired samples obtained within 1–2 weeks, 80% showed a CXCL10/creatinine ratio change of < ±2 ng/mmol or ±50%, respectively.

Conclusions.

Urine CXCL10 measurement on the used platform is accurate and robust. Leucocyturia and active BK-polyomavirus infection are major confounders, which can be easily detected but represent important diagnostic “blind spots” when using urine CXCL10 to screen for allograft rejection. The intraindividual biological variability of urine CXCL10 within 1–2 weeks is mostly below ±50%, which is still much higher than the technical variability due to sample handling/processing (<20%).

The prognostic value of urinary chemokines at 6 months after pediatric kidney transplantation

Pediatric kidney transplantation is lifesaving, but long-term allograft survival is still limited by injury processes mediated by alloimmune inflammation that may otherwise be clinically silent. Chemokines associated with alloimmune inflammation may offer prognostic value early post-transplant by identifying patients at increased risk of poor graft outcomes. We conducted a single-center prospective cohort study of consecutive pediatric kidney transplant recipients (<19 years). Urinary CCL2 and CXCL10 measured at 6 months post-transplant were evaluated for association with long-term eGFR decline, allograft survival, and concomitant acute cellular rejection histology. Thirty-eight patients with a mean age of 12.4 ± 4.6 years were evaluated. Urinary CCL2 was associated with eGFR decline until 6 months (ρ -0.43; P < .01), but not at later time points. Urinary CXCL10 was associated with eGFR decline at 36 months (ρ -0.49; P < .01), risk of 50% eGFR decline (HR = 1.04; P = .02), risk of allograft loss (HR = 1.05; P = .01), borderline rejection or rejection episodes 6-12 months post-transplant (r .41; P = .02), and Banff i + t score (r .47, P < .01). CCL2 and CXCL10 were also correlated with one another (ρ 0.54; P < .01). CCL2 and CXCL10 provide differing, but complementary, information that may be useful for early non-invasive prognostic testing in pediatric kidney transplant recipients.

Chronic inflammatory lesions of the placenta are associated with an up-regulation of amniotic fluid CXCR3: A marker of allograft rejection

OBJECTIVE

The objective of this study is to determine whether the amniotic fluid (AF) concentration of soluble CXCR3 and its ligands CXCL9 and CXCL10 changes in patients whose placentas show evidence of chronic chorioamnionitis or other placental lesions consistent with maternal anti-fetal rejection.

METHODS

This retrospective case-control study included 425 women with (1) preterm delivery (n=92); (2) term in labor (n=68); and (3) term not in labor (n=265). Amniotic fluid CXCR3, CXCL9 and CXCL10 concentrations were determined by ELISA.

RESULTS

(1) Amniotic fluid concentrations of CXCR3 and its ligands CXCL9 and CXCL10 are higher in patients with preterm labor and maternal anti-fetal rejection lesions than in those without these lesions [CXCR3: preterm labor and delivery with maternal anti-fetal rejection placental lesions (median, 17.24 ng/mL; IQR, 6.79-26.68) vs. preterm labor and delivery without these placental lesions (median 8.79 ng/mL; IQR, 4.98-14.7; P=0.028)]; (2) patients with preterm labor and chronic chorioamnionitis had higher AF concentrations of CXCL9 and CXCL10, but not CXCR3, than those without this lesion [CXCR3: preterm labor with chronic chorioamnionitis (median, 17.02 ng/mL; IQR, 5.57-26.68) vs. preterm labor without chronic chorioamnionitis (median, 10.37 ng/mL; IQR 5.01-17.81; P=0.283)]; (3) patients with preterm labor had a significantly higher AF concentration of CXCR3 than those in labor at term regardless of the presence or absence of placental lesions.

CONCLUSION

Our findings support a role for maternal anti-fetal rejection in a subset of patients with preterm labor.

Urinary miR-155-5p and CXCL10 as prognostic and predictive biomarkers of rejection, graft outcome and treatment response in kidney transplantation

AIMS

MicroRNAs (miRNAs) may be useful biomarkers of rejection and allograft outcome in kidney transplantation. Elevated urinary CXCL10 levels have been associated with acute rejection (AR) and may predict allograft failure. We examined the correlation of miRNA, CXCL10 levels and immunosuppressive drug exposure with AR and graft function in kidney transplant recipients.

METHODS

Eighty de novo kidney transplant recipients were recruited from four European centres. All patients received tacrolimus, mycophenolate mofetil, and methylprednisolone. Urinary pellet expression of miR-142-3p, miR-210-3p and miR-155-5p was assessed by quantitative real-time polymerase chain reaction and urinary CXCL10 levels by enzyme-linked immunosorbent assay at the 1^st week and the 1^st , 2^nd , 3^rd and 6^th months post-transplantation.

RESULTS

Eight patients experienced AR. Before and during AR, patients showed a significant increase of urinary miR-142-3p, miR-155-5p and CXCL10 levels and a decrease of miR-210-3p levels. Receiver operating characteristic curve analysis showed that miR-155-5p (area under the curve = 0.875; P = 0.046) and CXCL10 (area under the curve = 0.865; P = 0.029) had excellent capacity to discriminate between rejectors and nonrejectors. The optimal cut-off values for the prognosis of AR were 0.51, with 85% sensitivity and 86% specificity for miR-155-5p and 84.73 pg ml^-1 , with 84% sensitivity and 80% specificity for CXCL10. miR-155-5p and CXCL10 levels correlated with glomerular filtration rate. Levels of both biomarkers normalized after recovery of graft function.

CONCLUSIONS

The regular early post-transplantation monitoring of urinary miR-155-5p and CXCL10 can help in the prognosis of AR and graft dysfunction. Large prospective randomized multicentre trials are warranted to refine our cut-off values and validate the clinical usefulness of these biomarkers.

Chemokines and Their Receptors in Islet Allograft Rejection and as Targets for Tolerance Induction

Graft rejection is a major barrier to successful outcome of transplantation surgery. Islet transplantation introduces insulin secreting tissue into type 1 diabetes mellitus recipients, relieving patients from exogenous insulin injection. However, insulitis of grafted tissue and allograft rejection prevent long-term insulin independence. Leukocyte trafficking is necessary for the launch of successful immune responses to pathogen or allograft. Chemokines, small chemotactic cytokines, direct the migration of leukocytes through their interaction with chemokine receptors found on cell surfaces of immune cells. Unique receptor expression of leukocytes, and the specificity of chemokine secretion during various states of immune response, suggest that the extracellular chemokine milieu specifically homes certain leukocyte subsets. Thus, only those leukocytes required for the current immune task are attracted to the inflammatory site. Chemokine blockade, using antagonists and monoclonal antibodies directed against chemokine receptors, is an emerging and specific immunosuppressive strategy. Importantly, chemokine blockade may potentiate tolerance induction regimens to be used following transplantation surgery, and prevent the need for life-long immunosuppression of islet transplant recipients. Here, the role for chemokine blockade in islet transplant rejection and tolerance is reviewed.

Six-Month Urinary CCL2 and CXCL10 Levels Predict Long-term Renal Allograft Outcome

BACKGROUND

Early prognostic markers that identify high-risk patients could lead to increased surveillance, personalized immunosuppression, and improved long-term outcomes. The goal of this study was to validate 6-month urinary chemokine ligand 2 (CCL2) as a noninvasive predictor of long-term outcomes and compare it with 6-month urinary CXCL10.

METHODS

A prospective, observational renal transplant cohort (n = 185; minimum, 5-year follow-up) was evaluated. The primary composite outcome included 1 or more: allograft loss, renal function decline (>20% decrease estimated glomerular filtration rate between 6 months and last follow-up), and biopsy-proven rejection after 6 months. CCL2/CXCL10 are reported in relation to urine creatinine (ng/mmol).

RESULTS

Fifty-two patients (52/185, 28%) reached the primary outcome at a median 6.0 years, and their urinary CCL2:Cr was significantly higher compared with patients with stable allograft function (median [interquartile range], 38.6 ng/mmol [19.7-72.5] vs 25.9 ng/mmol [16.1-45.8], P = 0.009). Low urinary CCL2:Cr (≤70.0 ng/mmol) was associated with 88% 5-year event-free survival compared with 50% with high urinary CCL2:Cr (P < 0.0001). In a multivariate Cox-regression model, the only independent predictors of the primary outcome were high CCL2:Cr (hazard ratio [HR], 2.86; 95% confidence interval [95% CI], 1.33-5.73) and CXCL10:Cr (HR, 2.35; 95% CI, 1.23-4.88; both P = 0.009). Urinary CCL2:Cr/CXCL10:Cr area under the curves were 0.62 (P = 0.001)/0.63 (P = 0.03), respectively. Time-to-endpoint analysis according to combined high or low urinary chemokines demonstrates that endpoint-free survival depends on the overall early chemokine burden.

CONCLUSIONS

This study confirms that urinary CCL2:Cr is an independent predictor of long-term allograft outcomes. Urinary CCL2:Cr/CXCL10:Cr alone have similar prognostic performance, but when both are elevated, this suggests a worse prognosis. Therefore, urinary chemokines may be a useful tool for timely identification of high-risk patients.

Barcelona Consensus on Biomarker-Based Immunosuppressive Drugs Management in Solid Organ Transplantation

With current treatment regimens, a relatively high proportion of transplant recipients experience underimmunosuppression or overimmunosuppression. Recently, several promising biomarkers have been identified for determining patient alloreactivity, which help in assessing the risk of rejection and personal response to the drug; others correlate with graft dysfunction and clinical outcome, offering a realistic opportunity for personalized immunosuppression. This consensus document aims to help tailor immunosuppression to the needs of the individual patient. It examines current knowledge on biomarkers associated with patient risk stratification and immunosuppression requirements that have been generally accepted as promising. It is based on a comprehensive review of the literature and the expert opinion of the Biomarker Working Group of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology. The quality of evidence was systematically weighted, and the strength of recommendations was rated according to the GRADE system. Three types of biomarkers are discussed: (1) those associated with the risk of rejection (alloreactivity/tolerance), (2) those reflecting individual response to immunosuppressants, and (3) those associated with graft dysfunction. Analytical aspects of biomarker measurement and novel pharmacokinetic-pharmacodynamic models accessible to the transplant community are also addressed. Conventional pharmacokinetic biomarkers may be used in combination with those discussed in this article to achieve better outcomes and improve long-term graft survival. Our group of experts has made recommendations for the most appropriate analysis of a proposed panel of preliminary biomarkers, most of which are currently under clinical evaluation in ongoing multicentre clinical trials. A section of Next Steps was also included, in which the Expert Committee is committed to sharing this knowledge with the Transplant Community in the form of triennial updates.

Netrin-1 Augments Chemokinesis in CD4+ T Cells In Vitro and Elicits a Proinflammatory Response In Vivo

Netrin-1 is a neuronal guidance cue that regulates cellular activation, migration, and cytoskeleton rearrangement in multiple cell types. It is a chemotropic protein that is expressed within tissues and elicits both attractive and repulsive migratory responses. Netrin-1 has recently been found to modulate the immune response via the inhibition of neutrophil and macrophage migration. However, the ability of Netrin-1 to interact with lymphocytes and its in-depth effects on leukocyte migration are poorly understood. In this study, we profiled the mRNA and protein expression of known Netrin-1 receptors on human CD4(+) T cells. Neogenin, uncoordinated-5 (UNC5)A, and UNC5B were expressed at low levels in unstimulated cells, but they increased following mitogen-dependent activation. By immunofluorescence, we observed a cytoplasmic staining pattern of neogenin and UNC5A/B that also increased following activation. Using a novel microfluidic assay, we found that Netrin-1 stimulated bidirectional migration and enhanced the size of migratory subpopulations of mitogen-activated CD4(+) T cells, but it had no demonstrable effects on the migration of purified CD4(+)CD25(+)CD127(dim) T regulatory cells. Furthermore, using a short hairpin RNA knockdown approach, we observed that the promigratory effects of Netrin-1 on T effectors is dependent on its interactions with neogenin. In the humanized SCID mouse, local injection of Netrin-1 into skin enhanced inflammation and the number of neogenin-expressing CD3(+) T cell infiltrates. Neogenin was also observed on CD3(+) T cell infiltrates within human cardiac allograft biopsies with evidence of rejection. Collectively, our findings demonstrate that Netrin-1/neogenin interactions augment CD4(+) T cell chemokinesis and promote cellular infiltration in association with acute inflammation in vivo.

Computational immuno-biology for organ transplantation and regenerative medicine

Organ transplantation and regenerative medicine are adopted platforms that provide replacement tissues and organs from natural or engineered sources. Acceptance, tolerance and rejection depend greatly on the proper control of the immune response against graft antigens, motivating the development of immunological and genetical therapies that prevent organ failure. They rely on a complete, or partial, understanding of the immune system. Ultimately, they are innovative technologies that ensure permanent graft tolerance and indefinite graft survival through the modulation of the immune system. Computational immunology has arisen as a tool towards a mechanistic understanding of the biological and physicochemical processes surrounding an immune response. It comprehends theoretical and computational frameworks that simulate immuno-biological systems. The challenge is centered on the multi-scale character of the immune system that spans from atomistic scales, during peptide-epitope and protein interactions, to macroscopic scales, for lymph transport and organ-organ reactions. In this paper, we discuss, from an engineering perspective, the biological processes that are involved during the immune response of organ transplantation. Previous computational efforts, including their characteristics and visible limitations, are described. Finally, future perspectives and challenges are listed to motivate further developments.

Senescence in chronic allograft nephropathy

Despite increasing numbers of patients on dialysis, the numbers of renal transplants performed yearly have remained relatively static. During the last 50 years, there have been many advances in the pharmacology of prevention of organ rejection. However, most patients will suffer from a slow but steady decline in renal function leading to graft loss. The most common cause of long-term graft loss is chronic allograft nephropathy (CAN). Therefore, elucidating and understanding the mechanisms involved in CAN is crucial for achieving better posttransplant outcomes. It is thought that the development of epithelial to mesenchymal transition (EMT) in proximal tubules is one of the first steps towards CAN, and has been shown to be a result of cellular senescence. Cells undergoing senescence acquire a senescence associated secretory phenotype (SASP) leading to the production of interleukin-1 alpha (IL-1α), which has been implicated in several degenerative and inflammatory processes including renal disease. A central mediator in SASP activation is the production of reactive oxygen species (ROS), which are produced in response to numerous physiological and pathological stimuli. This review explores the connection between SASP and the development of EMT/CAN in an effort to suggest future directions for research leading to improved long-term graft outcomes.

Chemokine Detection Using Receptors Immobilized on an SPR Sensor Surface

Chemokines and their receptors take part in many physiological and pathological processes, and their dysregulated expression is linked to chronic inflammatory and autoimmune diseases, immunodeficiencies, and cancer. The chemokine receptors, members of the G protein-coupled receptor family, are integral membrane proteins, with seven-transmembrane domains that bind the chemokines and transmit signals through GTP-binding proteins. Many assays used to study the structure, conformation, or activation mechanism of these receptors are based on ligand-binding measurement, as are techniques to detect new agonists and antagonists that modulate chemokine function. Such methods require labeling of the chemokine and/or its receptor, which can alter their binding characteristics. Surface plasmon resonance (SPR) is a powerful technique for analysis of the interaction between immobilized receptors and ligands in solution, in real time, and without labeling. SPR measurements nonetheless require expression and purification steps that can alter the conformation, stability, and function of the chemokine and/or the chemokine receptor. In this review, we focus on distinct methods to immobilize chemokine receptors on the surface of an optical biosensor. We expose the advantages and disadvantages of different protocols used and describe in detail the method to retain viral particles as receptor carriers that can be used for SPR determinations.

Oscillatory mTOR inhibition and Treg increase in kidney transplantation

Intracellular metabolic pathways dependent upon the mammalian target of rapamycin (mTOR) play a key role in immune-tolerance control. In this study, we focused on long-term mTOR-dependent immune-modulating effects in kidney transplant recipients undergoing conversion from calcineurin inhibitors (CNI) to mTOR inhibitors (everolimus) in a 1-year follow-up. The conversion to everolimus is associated with a decrease of neutrophils and of CD8(+) T cells. In addition, we observed a reduced production of interferon (IFN)-γ by CD8(+) T cells and of interleukin (IL)-17 by CD4(+) T lymphocytes. An increase in CD4(+) CD25(+) forkhead box protein 3 (FoxP3)(+) [regulatory T cell [(Treg)] numbers was also seen. Treg increase correlated with a higher proliferation rate of this regulatory subpopulation when compared with the CD4(+) FoxP3(-) effector counterpart. Basal phosphorylation level of S6 kinase, a major mTOR-dependent molecular target, was substantially maintained in patients treated with everolimus. Moreover, oscillations in serum concentration of everolimus were associated with changes in basal and activation-dependent S6 kinase phosphorylation of CD4(+) and CD8(+) T cells. Indeed, T cell receptor (TCR) triggering was observed to induce significantly higher S6 kinase phosphorylation in the presence of lower everolimus serum concentrations. These results unveil the complex mTOR-dependent immune-metabolic network leading to long-term immune-modulation and might have relevance for novel therapeutic settings in kidney transplants.

Developing renal allograft surveillance strategies - urinary biomarkers of cellular rejection

Purpose of review

Developing tailored immunosuppression regimens requires sensitive, non-invasive tools for serial post-transplant surveillance as the current clinical standards with serum creatinine and proteinuria are ineffective at detecting subclinical rejection. The purpose of this review is: (i) to illustrate the rationale for allograft immune monitoring, (ii) to discuss key steps to bring a biomarker from bench-to-bedside, and (iii) to present an overview of promising biomarkers for cellular rejection.

Sources of information

PubMed.

Findings

Recent multicentre prospective observational cohort studies have significantly advanced biomarker development by allowing for the adequately powered evaluation of multiple biomarkers capable of detecting allograft rejection. These studies demonstrate that urinary CXCR3 chemokines (i.e. CXCL9 and CXCL10) are amongst the most promising for detecting subclinical inflammation; increasing up to 30 days prior to biopsy-proven acute rejection; decreasing in response to anti-rejection therapy; and having prognostic significance for the subsequent development of allograft dysfunction. Urinary CXCR3 chemokines are measured by simple and cost-effective ELISA methodology, which can readily be implemented in clinical labs.

Limitations

Many biomarker studies are performed in highly selected patient groups and lack surveillance biopsies to accurately classify healthy transplants. Few validation studies have been done in unselected, consecutive patient populations to characterize population-based diagnostic performance.

Implications

Based on these data, prospective interventional trials should be undertaken to determine if chemokine-based post-transplant monitoring strategies can improve long-term renal allograft outcomes. This last step will be necessary to move novel biomarkers from the bench-to-bedside.

Biomarkers to assess donor-reactive T-cell responses in kidney transplant patients

Different to antibody-mediated rejection (ABMR), T-cell mediated rejection (TCMR) still unpredictably occurs after kidney transplantation in a great part because of a poor immunologic evaluation of the cellular allogeneic immune response. However, in the last years, important efforts have focused on the development of novel and more sensitive assays to monitor T-cell alloimmune responses at different biological levels that may improve the understanding of the functional status of the cellular immune compartment in patients undergoing organ transplantation. In this direction, immune assays evaluating T-cell proliferation, intracellular ATP release, multiparameter flow cytometry, profiling T-cell receptor repertoires and measurements of frequencies of cytokine-producing T-cells using an IFN-γ enzyme-linked immunospot assay (IFN-γ ELISPOT) have been reported showing interesting associations between the cellular alloimmune response and kidney transplant outcomes. In summary, an important progress has been made in the assessment of alloreactive T-cell responses in the context of organ transplantation using novel immune assays at different biological levels. However, there is an urgent need for prospective, randomized clinical studies to validate these encouraging preliminary data to ultimately introduce them in current clinical practice for refining current immune-risk stratification in kidney transplantation.

Characterization of Innate Immunity in an Extended Whole Blood Model of Human Islet Allotransplantation

The instant blood-mediated inflammatory reaction (IBMIR) has been studied in whole blood models of human allo-islet transplantation for short periods (<6 h). Beyond this time frame the innate response to intraportally transplanted islets is less well described. A novel whole blood model was applied to study blood-islet-graft interactions up to 48 h. Heparinized polyvinyl chloride tubing was sealed into small bags containing venous blood together with allogeneic human islets and exocrine tissue, respectively. The bags were attached to a rotating wheel (37°C). Concentrated glucose and sodium hydrogen carbonate were added every 12 h to maintain physiological limits for sustained immune cell functions. Plasma was collected at repeated time points for analyses of coagulation/complement activation and chemokine/cytokine production. Immune cell infiltration was analyzed using immunohistochemistry. Coagulation and platelet activation markers, thrombin-antithrombin complex (TAT) and soluble CD40 ligand (sCD40L) showed early high concentrations (at 6-12 h). sC5b-9 steadily increased over 48 h. At 6 h neutrophils and monocytes surrounded the clotted cellular grafts with a following massive infiltration of neutrophils. High and increasing concentrations of CXCR1/2 ligands [IL-8 and growth-regulated oncogene α/β/γ (Gro-α/β/γ)] and IL-6 were produced in response to human islets and exocrine tissue. The CCR2 ligand monocyte chemoattractant protein 1 (MCP-1) exhibited increasing concentrations in response to exocrine tissue. The CXCR3 ligand interferon-inducible T cell α chemoattractant (I-TAC) was produced in response to both human islets and exocrine tissue from 6 h. Monokine induced by γ interferon (Mig) and interferon γ-induced protein 10 (IP-10) showed a later response, preferentially to exocrine tissue and with larger variations among preparations. An extended blood model of clinical islet transplantation allowed characterization of early immune activation in response to human islets and exocrine tissue. Increased production of chemokines targeting CXCR1/2, CCR2, and CXCR3 was observed, accompanied by massive intraislet neutrophil infiltration over 48 h. The model proved to be useful in exploring early blood-mediated reactions to cellular transplants and has relevance for evaluation of pharmacological interventions to prevent graft loss.

Elevated urinary CXCL10-to-creatinine ratio is associated with subclinical and clinical rejection in pediatric renal transplantation

BACKGROUND

Subclinical and clinical T cell-mediated rejection (TCMR) has significant prognostic implications in pediatric renal transplantation. The goal of this study was to independently validate urinary CXCL10 as a noninvasive biomarker for detecting acute rejection in children and to extend these findings to subclinical rejection.

METHODS

Urines (n = 140) from 51 patients with surveillance or indication biopsies were assayed for urinary CXCL10 using enzyme-linked immunosorbent assay and corrected with urinary creatinine.

RESULTS

Median urinary CXCL10-to-creatinine (Cr) ratio (ng/mmol) was significantly elevated in subclinical TCMR (4.4 [2.6, 25.4], P < 0.001, n = 17); clinical TCMR (24.3 [11.2, 44.8], P < 0.001, n = 9); and antibody-mediated rejection (6.0 [3.3, 13.7], P = 0.002, n = 9) compared to noninflamed histology (1.4 [0.4, 4.2], normal and interstitial fibrosis and tubular atrophy, n = 52), and borderline tubulitis (3.3, [1.3, 4.9], n = 36). Elevated urinary CXCL10:Cr was independently associated with t scores (P < 0.001) and g scores (P = 0.006) on multivariate analysis. The area under receiver operating curve for subclinical and clinical TCMR was 0.81 (P = 0.045) and 0.88 (P = 0.019), respectively. This corresponded to a sensitivity-specificity of 0.59-0.67 and 0.77-0.60 for subclinical and clinical TCMR at cutoffs of 4.82 and 4.72 ng/mmol, respectively.

CONCLUSION

This study demonstrates that urinary CXCL10:Cr corresponds with microvascular inflammation and is a sensitive and specific biomarker for subclinical and clinical TCMR in children. This may provide a noninvasive monitoring tool for posttransplant immune surveillance for pediatric renal transplant recipients.

Peroxisome proliferator-activated receptor γ deficiency in T cells accelerates chronic rejection by influencing the differentiation of CD4+ T cells and alternatively activated macrophages

Background

In a previous study, activation of the peroxisome proliferator–activated receptor γ (PPARγ) inhibited chronic cardiac rejection. However, because of the complexity of chronic rejection and the fact that PPARγ is widely expressed in immune cells, the mechanism of the PPARγ - induced protective effect was unclear.

Materials and Methods

A chronic rejection model was established using B6.C-H-2^bm12KhEg (H-2^bm12) mice as donors, and MHC II-mismatched T-cell-specific PPARγ knockout mice or wild type (WT) littermates as recipients. The allograft lesion was assessed by histology and immunohistochemistry. T cells infiltrates in the allograft were isolated, and cytokines and subpopulations were detected using cytokine arrays and flow cytometry. Transcription levels in the allograft were measured by RT-PCR. In vitro, the T cell subset differentiation was investigated after culture in various polarizing conditions. PPARγ-deficient regularory T cells (Treg) were cocultured with monocytes to test their ability to induce alternatively activated macrophages (AAM).

Results

T cell-specific PPARγ knockout recipients displayed reduced cardiac allograft survival and an increased degree of pathology compared with WT littermates. T cell-specific PPARγ knockout resulted in more CD4+ T cells infiltrating into the allograft and altered the Th1/Th2 and Th17/Treg ratios. The polarization of AAM was also reduced by PPARγ deficiency in T cells through the action of Th2 and Treg. PPARγ-deficient T cells eliminated the pioglitazone-induced polarization of AAM and reduced allograft survival.

Conclusions

PPARγ-deficient T cells influenced the T cell subset and AAM polarization in chronic allograft rejection. The mechanism of PPARγ activation in transplantation tolerance could yield a novel treatment without side effects.

Transplantation and inflammation: implications for the modification of chemokine function

Oxidative stress is a major and recurring cause of damage during inflammation, especially following organ transplantation. Initial ischaemia–reperfusion injury causes the production of many reactive oxygen and nitrogen species, and subsequent recruitment and activation of inflammatory cells can lead to further oxidative stress. This stress is well known to cause damage at the cellular level, for example by induction of senescence leading to the production of a characteristic senescence-associated secretory phenotype. Chemokines are an important component of the senescence-associated secretory phenotype, recruiting further leucocytes and reinforcing the stress and senescence responses. As well as inducing the production of proteins, including chemokines, oxidative stress can alter proteins themselves, both directly and by induction of enzymes capable of modification. These alterations can lead to important modifications to their biological activity and also alter detection by some antibodies, potentially limiting the biological relevance of some immunochemical and proteomic biomarkers. Peroxynitrite, a reactive nitrogen species generated during inflammation and ischaemia, can cause such modifications by nitrating chemokines. Matrix metalloproteinases, released by many stressed cells, can cleave chemokines, altering function, while peptidylarginine deiminases can inactivate certain chemokines by citrullination. This review discusses the relationship between inflammation and post-translational modification, focusing on the functional modulation of transplant-relevant pro-inflammatory chemokines.

Effect of everolimus on the immunomodulation of the human neutrophil inflammatory response and activation

The primary cause of mortality at 5 years following a cardiac transplantation is the development of atherosclerosis, termed coronary allograft vasculopathy (CAV). This pathology is characterized by diffused intimal hyperplasia and emanates from coronary arterial injuries caused by immune inflammatory cells. Neutrophils play an important role in this inflammatory process; however, their potential participation in the pathogenesis of CAV is poorly understood. Despite their essential contribution to the prevention of graft rejection, immunosuppressive drugs could have detrimental effects owing to their pro-inflammatory activities. Thus, we investigated the impact of different immunosuppressive drugs on the inflammatory response of neutrophils isolated from the blood of healthy volunteers. Under basal conditions, mammalian target of rapamycin (mTOR) inhibitors (sirolimus and everolimus) had the most potent anti-inflammatory effect, decreasing both IL-8 release (≈−80%) and vascular endothelial growth factor (VEGF) release (≈−65%) and preserving the release of the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1RA). In TNF-α-treated neutrophils, pre-incubation with everolimus provided the most potent effect, simultaneously reducing the release of both VEGF and IL-8 while doubling the release of IL-1RA. This latter effect of everolimus was maintained even when administered in combination with other immunosuppressive drugs. Sirolimus and everolimus decreased the tumor necrosis factor (TNF)-α-induced adhesion of neutrophils to human endothelial cells and human extracellular matrix. This effect was largely dependent on the ability of these compounds to alter β₂-integrin/CD18 activation. Our results suggest a potential mechanism for the beneficial effect of everolimus in the prevention of CAV in heart transplant recipients.

The immunosuppressant Protosappanin A diminished recipient T cell migration into allograft via inhibition of IP-10 in rat heart transplant

The immunosuppressant Protosappanin A (PrA), isolated from the medicinal herb, promotes cardiac allograft survival, diminishes inflammatory cell infiltration, and inhibits interferon γ-induced protein 10 kDa (IP-10) mRNA expression in rats cardiac grafts. Binding of the chemokine IP-10 to its cognate receptor, CXCR3, plays crucial roles in allograft immunity, especially by mediating the recruitment of effector T cells to allografted tissues. In this study, we attempted to determine whether PrA-mediated inhibition of IP-10 contributes to the effect of reduced T cell infiltration into cardiac allograft within a rat model. Administration of PrA (25 mg/kg daily) via oral gavage following heart transplantation significantly reduced the increase of IP-10 mRNA level in allograft and prevented IP-10 secretion by peripheral blood mononuclear cells (PBMC) isolated from recipient rats seven days posttransplantation. Furthermore, in vitro experiments demonstrated that PrA addition to control PBMC prevented IP-10 secretion. Chemotactic migration assays were utilized to evaluate recipient T cell migration towards PBMC supernatant. PrA administration impaired PBMC supernatant-induced T cell migration. Additional in vitro experiments revealed that PrA slightly reduced naïve T cell migration towards chemokines. The presence of IP-10 in PBMC supernatant prevented PrA from reducing T cell migration in PrA-treated recipients. Neither CXCR3 chemokine ligand Mig nor non-CXCR3 chemokine ligand SDF-1 had any effect on T cell migration in PrA-treated recipients. The addition of anti-CXCR3 antibody restored PrA-mediated inhibition of T cell migration. Immunofluorescence microscopy showed that IP-10 was expressed mainly in CD68 positive infiltrating monocytes. Furthermore, PrA consistently reduced CXCR3+T cell infiltration into cardiac allografts. The reduced intensity of CXCR3 staining in PrA-treated allografts contributed to the previously depressed naïve T cell migrating activity induced by PrA. Collectively, these data indicate that PrA inhibition of IP-10 activity reduced recipient T cell migration and infiltration of cardiac allografts, thus partially explaining the immunosuppressive effect of PrA.

Biomarkers for kidney transplant rejection

The immune management of organ transplant recipients is imperfect. Beyond general dosing guidelines for immunosuppressive agents and clinical diagnostic tests for rejection or infection, there are few objective tools to determine the aggregate status of a patient's alloimmune response or protective immune capacity. The lack of prognostic precision significantly contributes to patient morbidity and reduces long-term allograft survival after kidney transplantation. Noninvasive biomarkers that could serve as predictive tools or surrogate end points for rejection might help clinicians individualize immunosuppression and allow for early intervention, ideally prior to clinically evident organ dysfunction. Although the growing understanding of organ rejection has provided numerous candidate biomarkers, none has been confirmed in robust validation studies as sufficiently useful to guide clinical practice independent of traditional clinical methods. In this Review, the general characteristics of biomarkers and surrogate end points; current biomarkers under active clinical investigation; and the prominent barriers to the translation of biomarkers into clinical practice are discussed.

Detection of IP-10 protein marker in undiluted blood serum via an electrochemical E-DNA scaffold sensor

We describe an electrochemical analog of fluorescence polarization that supports the quantitative measurement of a specific protein, the chemokine IP-10, directly in undiluted blood serum. The sensor is label-free, wash-free, and electronic, suggesting it could support point-of-care detection of diagnostic proteins in largely unprocessed clinical samples.

Endothelium and Regulatory Inflammatory Mechanisms During Organ Rejection

Endothelial integrity is mandatory for physiologic organ function; however, endothelium dysfunction can be caused by systemic inflammation, occurring during sepsis or organ rejection after transplantation. This article will address our current understanding of endothelial involvement in organ transplantation and rejection. Overall, more detailed studies focusing on the endothelial modulation after organ transplantation would be necessary to investigate the role of endothelium activation during organ rejection.

Inflammatory markers sampled by microdialysis catheters distinguish rejection from ischemia in liver grafts

Rejection and ischemia are serious complications after liver transplantation. Early detection is mandatory, but specific markers are largely missing, particularly for rejection. The objective of this study was to explore the ability of microdialysis catheters inserted in liver grafts to detect and discriminate rejection and ischemia through postoperative measurements of inflammatory mediators. Microdialysis catheters with a 100-kDa pore size were inserted into 73 transplants after reperfusion. After the study's completion, complement activation product 5a (C5a), C-X-C motif chemokine 8 (CXCL8), CXCL10, interleukin-1 (IL-1) receptor antagonist, IL-6, IL-10, and macrophage inflammatory protein 1β were analyzed en bloc in all grafts with biopsy-confirmed rejection (n = 12), in grafts with vascular occlusion/ischemia (n = 4), and in reference grafts with a normal postoperative course of circulating transaminase and bilirubin levels (n = 17). The inflammatory mediators were elevated immediately after graft reperfusion and decreased toward low, stable values during the first 24 hours in nonischemic grafts. In grafts suffering from rejection, CXCL10 increased significantly (P = 0.008 versus the reference group and P = 0.002 versus the ischemia group) 2 to 5 days before increases in circulating alanine aminotransferase and bilirubin levels. The area under the receiver operating characteristic curve was 0.81. Grafts with ischemia displayed increased levels of C5a (P = 0.002 versus the reference group and P = 0.008 versus the rejection group). The area under the curve was 0.99. IL-6 and CXCL8 increased with both ischemia and rejection. In conclusion, CXCL10 and C5a were found to be selective markers for rejection and ischemia, respectively.

Toll-like receptor 4 in experimental kidney transplantation: early mediator of endogenous danger signals

The role of toll-like receptors (TLRs) has been described in the pathogenesis of renal ischemia/reperfusion injury, but data on the expression and function of TLR4 during renal allograft damage are still scarce. We analyzed the expression of TLR4 in an experimental rat model 6 and 28 days after allogeneic kidney transplantation in comparison to control rats and rats after syngeneic transplantation. On day 6, a significant induction in TLR4 expression--restricted to the glomerular compartment--was found in acute rejecting allografts only. TLR4 expression strongly correlated with renal function, and TLR4 induction was accompanied by a significant increase in CC chemokine expression within the graft as well as in urinary CC chemokine excretion. TLR4 induction may be caused by an influx of macrophages as well as TLR4-expressing intrinsic renal cells. Fibrinogen deposition in renal allografts correlated with renal TLR4 expression and may act as a potent stimulator of chemokine release via TLR4 activation. This study provides, for the first time, data about the precise intrarenal localization and TLR4 induction after experimental kidney transplantation. It supports the hypothesis that local TLR4 activation by endogenous ligands may be one pathological link from unspecific primary allograft damage to subsequent chemokine release, infiltration and activation of immune cells leading to deterioration of renal function and induction of renal fibrosis.

Chemokine receptor oligomerization: a further step toward chemokine function

A broad array of biological responses including cell polarization, movement, immune and inflammatory responses, as well as prevention of HIV-1 infection, are triggered by the chemokines, a family of secreted and structurally related chemoattractant proteins that bind to class A-specific seven-transmembrane receptors linked to G proteins. Chemokines and their receptors should not be considered isolated entities, as they act in complex networks. Chemokines bind as oligomers, or oligomerize after binding to glycosaminoglycans on endothelial cells, and are then presented to their receptors on target cells, facilitating the generation of chemoattractant gradients. The chemokine receptors form homo- and heterodimers, as well as higher order structures at the cell surface. These structures are dynamic and are regulated by receptor expression and ligand levels. Complexity is even greater, as in addition to regulation by cytokines and decoy receptors, chemokine and receptor levels are affected by proteolytic cleavage and other protein modifications. This complex scenario should be considered when analyzing chemokine biology and the ability of their antagonists to act in vivo. Strategies based on blocking or stabilizing ligand and receptor dimers could be alternative approaches that might have broad therapeutic potential.

CXCL10: a candidate biomarker in transplantation

Interferon (IFN) γ-induced protein 10 kDa (IP-10) or C-X-C motif chemokine 10 (CXCL10) is a small cytokine belonging to the CXC chemokine family. This family of signaling molecules is known to control several biological functions and to also play pivotal roles in disease initiation and progression. By binding to its specific cognate receptor CXCR3, CXCL10 critically regulates chemotaxis during several immune-inflammatory processes. In particular, this chemokine controls chemotaxis during the inflammatory response resulting from allograft rejection after transplantation. Interestingly, a strong association has been described between CXCL10 production, immune response and the fate of the graft following allotransplantation. Enhanced CXCL10 production has been observed in recipients of transplants of different organs. This enhanced production likely comes from either the graft or the immune cells and is correlated with an increase in the concentration of circulating CXCL10. Because CXCL10 can be easily measured in the serum and plasma from a patient, the detection and quantitation of circulating CXCL10 could be used to reveal a transplant recipient's immune status. The purpose of this review is to examine the critical role of CXCL10 in the pathogenesis of allograft rejection following organ transplantation. This important role highlights the potential utilization of CXCL10 not only as a therapeutic target but also as a biomarker to predict the severity of rejection, to monitor the inflammatory status of organ recipients and, hopefully, to fine-tune patient therapy in transplantation.

Validation of urinary CXCL10 as a marker of borderline, subclinical, and clinical tubulitis

BACKGROUND

Renal allograft injury secondary to subclinical and clinical tubulitis remains an important cause of allograft fibrosis and loss despite modern immunosuppression. The goal of this study was to validate the previously reported use of urinary CXCL10 (interferon-γ-induced protein of 10 kDa) as a noninvasive marker of tubulitis in an independent clinical cohort.

METHODS

Urine samples (n=102) from 91 patients with protocol or indication biopsies were assayed for urinary CXCL10 using ELISA. The groups analyzed were as follows: normal histology (n=22); interstitial fibrosis and tubular atrophy (IFTA) (n=20); IFTA and borderline tubulitis (n=13); borderline (n=13), subclinical (n=17); and clinical tubulitis (n=17) without IFTA.

RESULTS

The ratio of urinary CXCL10 to creatinine (CXCL10: Cr) was found to distinguish borderline, subclinical and clinical tubulitis from normal histology, and IFTA. The area under the curve receiver operating characteristic curve to distinguish normal versus borderline and subclinical tubulitis was 0.845 (OR 1.407, P=0.0184); normal versus borderline, subclinical and clinical tubulitis was 0.835 (OR 1.400, P=0.0127). CXCL10: Cr demonstrated a sensitivity of 73.3% and specificity of 72.7% for normal versus borderline and subclinical tubulitis at a cut-off of 1.97 ng CXCL10/mmol Cr.

CONCLUSION

This study validates urinary CXCL10 as a noninvasive, sensitive, and specific marker for tubulitis in an independent cohort. The straightforward urine processing is accessible to clinical laboratories. We propose that CXCL10 may be useful as a supplementary noninvasive screening test for tubulitis in renal transplant patients, with a level more than 1.97 ng CXCL10/mmol Cr being a threshold to consider biopsy.

Surface markers of lymphocyte activation and markers of cell proliferation

The individualization of immunosuppression is an approach for preventing rejection in the early phase after transplantation and for avoiding the long-term side effects of over immunosuppression. Pharmacodynamic markers, either specific or nonspecific, have been proposed as complementary tools to drug monitoring of immunosuppressive drugs. A key event in graft rejection is the activation and proliferation of the recipient's lymphocytes, particularly T cells. Activated T cells express surface receptors, such as CD25 (the IL-2 receptor) and CD71 (the transferrin receptor), or co-stimulatory molecules (CD26, CD27, CD28, CD30, CD154 or CD40L, and CD134). Both surface marker expression and cell proliferation are predominately assessed by flow cytometry. Protocols have been established and utilized for both in vitro and ex vivo investigations with either isolated lymphocytes or whole blood. This article reviews the current body of research regarding the use of lymphocyte proliferation and surface activation markers with an emphasis on T cells. Experimental and clinical results related to these markers, as well as methodological issues and open questions, are addressed.

Role of cold shock Y-box protein-1 in inflammation, atherosclerosis and organ transplant rejection

Chemokines (chemoattractant cytokines) are crucial regulators of immune cell extravasation from the bloodstream into inflamed tissue. Dysfunctional regulation and perpetuated chemokine gene expression are linked to progressive chronic inflammatory diseases and, in respect to transplanted organs, may trigger graft rejection. RANTES (regulated upon activation, normal T cell expressed and secreted (also known as CCL5)) is a model chemokine with relevance in numerous inflammatory diseases where the innate immune response predominates. Transcription factor Y-box binding protein-1 (YB-1) serves as a trans-regulator of CCL5 gene transcription in vascular smooth muscle cells and leucocytes. This review provides an update on YB-1 as a mediator of inflammatory processes and focuses on the role of YB-1 in CCL5 expression in diseases with monocytic cell infiltrates, albeit acute or chronic. Paradigms of such diseases encompass atherosclerosis and transplant rejection where cold shock protein YB-1 takes a dominant role in transcriptional regulation.

Genetic polymorphisms of inflammatory molecules in Tunisian kidney transplantation

As chemokines and adhesion molecules play major roles in the process by which leukocytes are recruited from the bloodstream into sites of inflammation, genetic variations in the production or activity of molecules may influence susceptibility to acute rejection episodes. This study sought to determine the impact of recipient monocyte chemoattractant protein-1 (MCP-1), chemokine receptor (CCR2, CCR5), and adhesion molecule (ICAM-1, PECAM-1 and L/E selectin) polymorphisms on acute rejection after renal transplantation. We selected 169 healthy blood donors and 173 renal transplant recipients for analysis according to the presence or absence of graft rejection in the first 30 days after transplantation. Using molecular methods DNA was genotyped for 11 polymorphisms of these inflammatory molecules genes. Results were stratified by the incidence of rejection episodes and by human leukocyte antigen (HLA) mismatching. No association was detected between adhesion molecule polymorphisms and the incidence of acute rejection episodes. However, a significant risk of acute renal loss was observed among HLA-identical recipients who possessed the CCR2-64I allele (odds ratio 0.24, 95% confidence interval, 0.05 to 1.06; P=.035). In conclusion, the observed association of CCR2-64I with acute rejection episodes should be added to the spectrum of immunogenetic factors known to be involved in renal allograft rejection.

Inhibiting CXCR3-dependent CD8+ T cell trafficking enhances tolerance induction in a mouse model of lung rejection

Lung transplantation remains the only effective therapy for patients with end-stage pulmonary diseases. Unfortunately, acute rejection of the lung remains a frequent complication and is an important cause of morbidity and mortality. The induction of transplant tolerance is thought to be dependent, in part, on the balance between allograft effector mechanisms mediated by effector T lymphocytes (Teff), and regulatory mechanisms mediated by FOXP3(+) regulatory T cells (Treg). In this study, we explored an approach to tip the balance in favor of regulatory mechanisms by modulating chemokine activity. We demonstrate in an adoptive transfer model of lung rejection that CXCR3-deficient CD8(+) Teff have impaired migration into the lungs compared with wild-type Teff, which results in a dramatic reduction in fatal pulmonary inflammation. The lungs of surviving mice contained tolerized CXCR3-deficient Teff, as well as a large increase in Treg. We confirmed that Treg were needed for tolerance and that their ability to induce tolerance was dependent on their numbers in the lung relative to the numbers of Teff. These data suggest that transplantation tolerance can be achieved by reducing the recruitment of some, but not necessarily all, CD8(+) Teff into the target organ and suggest a novel approach to achieve transplant tolerance.