Intragraft interleukin 2 mRNA expression during acute cellular rejection and left ventricular total wall thickness after heart transplantation

Interleukin-17-producing CD4(+) cells home to the graft early after human heart transplantation

BACKGROUND

Interleukin-17 (IL-17) is regarded as a major effector cytokine with pro-inflammatory actions. It has pleiotropic and environment-specific functions by promoting adaptive cytotoxic T-lymphocyte responses during inflammation. Therefore, it is tempting to speculate that IL-17 plays a major role in inflammatory responses in transplant recipients. We questioned whether IL-17 is expressed in the transplanted heart during acute rejection (AR), or during immunologic quiescence, and which graft-infiltrating lymphocytes produce IL-17. In addition, we analyzed donor-specific IL-17-producing cells in peripheral blood cells in comparable periods after transplantation.

METHODS

Endomyocardial biopsies from heart transplant recipients with early or late AR or in an immunologic quiescence period were analyzed for the presence of IL-17 mRNA. In addition, the capacity of graft-infiltrating lymphocytes (GILs) to produce IL-17 was analyzed. Moreover, we determined the frequency of donor-reactive IL-17-producing peripheral blood mononuclear cells (PBMCs) using an Elispot assay.

RESULTS

Twenty-one percent (14 of 67) of the biopsies assessed were positive for IL-17 mRNA. Thirteen of 41 biopsies were observed in the early period (≤3 months) after transplantation. One (of 26) of the late biopsies expressed IL-17 (p = 0.006). Specifically, IL-17 was expressed during early AR (57%, or 8 of 14), whereas biopsies from late AR (0 of 5) did not express IL-17 mRNA (p = 0.02). During AR, IL-17 is derived from IL-17-producing CD4(+)CD161(+), and not CD8(+), GILs. In contrast to the graft findings, we detected circulating donor-reactive IL-17-producing cells mostly during immunologic quiescence.

CONCLUSIONS

Particularly early after heart transplantation, IL-17-producing CD4(+) T cells home to the graft, which contributes to the AR process.

Identification of common blood gene signatures for the diagnosis of renal and cardiac acute allograft rejection

To test, whether 10 genes, diagnostic of renal allograft rejection in blood, are able to diagnose and predict cardiac allograft rejection, we analyzed 250 blood samples from heart transplant recipients with and without acute rejection (AR) and with cytomegalovirus (CMV) infection by QPCR. A QPCR-based logistic regression model was built on 5 of these 10 genes (AR threshold composite score >37%  = AR) and tested for AR prediction in an independent set of 109 samples, where it correctly diagnosed AR with 89% accuracy, with no misclassifications for AR ISHLT grade 1b. CMV infection did not confound the AR score. The genes correctly diagnosed AR in a blood sample within 6 months prior to biopsy diagnosis with 80% sensitivity and untreated grade 1b AR episodes had persistently elevated scores until 6 months after biopsy diagnosis. The gene score was also correlated with presence or absence of cardiac allograft vasculopathy (CAV) irrespective of rejection grade. In conclusion, there is a common transcriptional axis of immunological trafficking in peripheral blood in both renal and cardiac organ transplant rejection, across a diverse recipient age range. A common gene signature, initially identified in the setting of renal transplant rejection, can be utilized serially after cardiac transplantation, to diagnose and predict biopsy confirmed acute heart transplant rejection.

Whole blood genomic biomarkers of acute cardiac allograft rejection

BACKGROUND

Significant progress has been made in cardiac transplantation over the past 30 years; however, the means for detection of acute cardiac allograft rejection remains in need of improvement. At present, the endomyocardial biopsy, an invasive and inconvenient procedure for patients, is required for the surveillance and diagnosis of acute cardiac allograft rejection. In the Biomarkers in Transplantation initiative, we investigated gene expression profiles in peripheral blood of cardiac transplant subjects as potential biomarkers for diagnosis of allograft rejection.

METHODS

Whole blood samples were obtained from 28 cardiac transplant subjects who consented to the study. Serial samples were collected from pre-transplant through 3 years post-transplant according to the standard protocol. Temporally correspondent biopsies were also collected, reviewed in a blinded manner, and graded according to current ISHLT guidelines. Blood samples were analyzed using Affymetrix microarrays. Genomic profiles were compared in subjects with acute rejection (AR; ISHLT Grade > or =2R) and no rejection (NR; Grade 0R). Biomarker panel genes were identified using linear discriminant analysis.

RESULTS

We found 1,295 differentially expressed probe-sets between AR and NR samples and developed a 12-gene biomarker panel that classifies our internal validation samples with 83% sensitivity and 100% specificity.

CONCLUSIONS

Based on our current results, we believe whole blood genomic biomarkers hold great potential in the diagnosis of acute cardiac allograft rejection. A prospective, Canada-wide trial will be conducted shortly to further evaluate the classifier panel in diverse patients and a range of clinical programs.

Value of FOXP3 expression in peripheral blood as rejection marker after miniature swine lung transplantation

BACKGROUND

Outcome for highly immunogenic lung transplantation remains unsatisfactory despite the development of potent immunosuppressants. The poor outcome may be the result of a lack of minimally invasive methods to detect early rejection. There is emerging clinical evidence that, paradoxically, expression of forkhead box P3 (FOXP3, a specific marker for the regulatory T cells) is upregulated within rejecting grafts.

METHODS

Orthotopic lung transplantation was performed using miniature swine without immunosuppression. Rejection was monitored by chest radiography and open lung biopsy. Expressions levels of FOXP3, perforin, Fas-L and IP-10 mRNA were quantified in the peripheral blood. In addition, rescue immunosuppressive therapy (steroid plus tacrolimus) was administered on post-operative day (POD) 4 or 6.

RESULTS

Early rejection was detected by open lung biopsy, but misdiagnosed by chest radiography on POD 4. Expression of FOXP3 in the peripheral blood reached its highest value as early as POD 4, followed by a decline. Such an increase of FOXP3 was not observed in recipients given high-dose tacrolimus. Neither perforin, Fas-L or IP-10 in the peripheral blood exhibited significant fluctuations in the early phase of rejection. Rescue immunosuppressive therapy from POD 4, when peak FOXP3 was seen, prolonged graft survival (27.2 days, versus 9.1 days without immunosuppression, p < 0.001), in contrast to POD 6, when rejection was suspected by chest radiography (11.5 days, p = not statistically significant [NS]).

CONCLUSIONS

In a miniature swine lung transplantation model, the FOXP3 mRNA level in the peripheral blood was upregulated at an early phase of rejection. The clinical implication of this finding remains to be elucidated.

Intragraft FOXP3 mRNA Expression Reflects Antidonor Immune Reactivity in Cardiac Allograft Patients

BACKGROUND

Regulatory FOXP3+ T cells control immune responses of effector T cells. However, whether these cells regulate antidonor responses in the graft of cardiac allograft patients is unknown. Therefore, we analyzed the gene expression profiles of regulatory and effector T-cell markers during immunological quiescence and acute rejection.

METHODS

Quantitative real-time polymerase chain reaction was used to analyze mRNA expression levels in time-zero specimens (n=24) and endomyocardial biopsies (EMB; n=72) of cardiac allograft patients who remained free from rejection (nonrejectors; n=12) and patients with at least one histologically proven acute rejection episode (rejectors; International Society for Heart and Lung Transplantation [ISHLT] rejection grade>2; n=12).

RESULTS

For all analyzed regulatory and effector T-cell markers, mRNA expression levels were increased in biopsies taken after heart transplantation compared with those in time-zero specimens. Posttransplantation, the FOXP3 mRNA levels were higher in EMB assigned to a higher ISHLT rejection grade than the biopsies with grade 0: the highest mRNA levels were detected in the rejection biopsies (rejection grade>2; P=0.003). In addition, the mRNA levels of CD25, glucocorticoid-induced TNF receptor family-related gene, cytotoxic T lymphocyte-associated antigen 4, interleukin-2, and granzyme B were also significantly higher in rejecting EMB than in nonrejecting EMB (rejection grade<or=2). This increase in expression levels in relation to the histological rejection grade was only observed in patients who developed an acute rejection episode; the mRNA levels of nonrejectors remained stable irrespective of ISHLT rejection grade.

CONCLUSIONS

These observations suggest that, after clinical heart transplantation, FOXP3+ T cells do not prevent acute rejection, but rather are a response to antidonor effector T-cell activity.

Functional CD25bright+alloresponsive T cells in fully immunosuppressed renal allograft recipients

BACKGROUND

Evidence from animal studies indicate a crucial role for CD25(bright+) regulatory T cells in transplantation tolerance.

METHODS

To assess whether peripheral CD25(bright+) T cells control immune responses in immunosuppressed kidney transplant patients, we analyzed the suppressive capacities of these cells using mixed lymphocytes reactions.

RESULTS

Allogeneic stimulation of patients peripheral blood mononuclear cells was associated with IL-2 production and T-cell proliferation. Depletion of CD25(bright+) T cells resulted in a 35% (median) higher IL-2 production and a 38% higher proliferative response against third party cells, showing that functional regulatory CD25(bright+) T cells were present (p = 0.03 and 0.02 respectively). In eight out of 11 patients, we also demonstrated regulation activity against donor-activated T cells (p = 0.03). These data were confirmed in coculture experiments with isolated CD25(-/dim) T cells plus CD25(bright+) T cells. At a 1:2 ratio, the CD25(bright+) T cells suppressed the proliferation of CD25(-/dim) donor- and third party-stimulated responder T cells.

CONCLUSIONS

CD25(bright+) T cells with immune regulatory activities against anti-donor-responsive T cells are readily detectable in renal allograft recipients during treatment with full dosage immunosuppression. Whether CD25(bright+) T cells indeed play a role in graft acceptance after organ transplantation in patients remains to be elucidated.

FoxP3+ T Cells Can Be Expanded From Rejecting Cardiac Allografts

A specific subset of T cells, the FoxP3+ regulatory T cells, control effector T-cell responses to self and foreign antigens. In transplant patients, we and others have shown that high intragraft FOXP3 mRNA levels are associated with acute rejection, suggesting that immune regulation is dependent on immune activation. To study whether transplanted grafts harbor FoxP3+ T cells and to functionally analyze them, graft infiltrating lymphocytes (GILs) must be propagated from the transplanted tissue. In the present study, we analyzed whether FoxP3+ T cells can be grown from endomyocardial biopsies (EMBs; n = 5) from patients after heart transplantation during acute cellular rejection. After 18 to 21 days of culture, 0.5 to 1.0 x 10(6) GILs were cultured from the EMBs. Of these GILs, 10.6% (median; range, 1.6%-17.1%) stained positive for FoxP3. Thus Foxp3+ T cells can be grown from EMBs, providing the tools to functionally characterize these cells in depth in forthcoming studies.

An Echocardiographic Left Ventricular Wall Area Index for Functional Detection of Myocardial Injury in Hemodynamically Unloaded Hearts

Functional assessment of the left ventricle is affected by loading conditions. Detection of rejection-mediated myocardial injury in a heterotopic heart transplant model is a challenge for the echocardiographer because the heart is in an unloaded state. We examined the relationship of a novel left ventricular (LV) wall area index (LVWAI) and serum cardiac troponin T (cTnT) levels. The LVWAI, based on prior methods of determining LV mass, was defined as the difference between epicardial and endocardial areas divided by the epicardial area. The biphasic morphometric response of LVWAI reflected changes in the cTnT levels and allowed echocardiographic detection of myocardial injury in hemodynamically unloaded hearts.

Differential effect of calcineurin inhibitors, anti-CD25 antibodies and rapamycin on the induction of FOXP3 in human T cells

BACKGROUND

The transcription factor FOXP3 has been identified as the molecule associated with the regulatory function of CD25+ T cells.

METHODS

To understand the biology of FOXP3+ T cells in allogeneic reactions, we measured FOXP3 mRNA expression levels in allostimulated CD25 cells and CD25 cells and in peripheral blood mononuclear cells (PBMC). The effect of immunosuppressive drugs on FOXP3 expression was studied in mixed lymphocyte reactions (MLR) in the presence and absence of calcineurin inhibitors (CNI), alphaCD25 mAb, and Rapamycin (Rapa), and analyzed in biopsies from cardiac allograft recipients during acute rejection by quantitative (Q)-PCR.

RESULTS

FOXP3 mRNA expression was restricted to the CD25 population that inhibited the proliferation of allostimulated CD25 cells. In the MLR FOXP3 was readily induced after allostimulation. Kinetic examination of the MLR showed a 10-20-fold higher FOXP3 mRNA expression level after 5 days of culture. The CNI Cyclosporin and Tacrolimus, and alphaCD25 mAb inhibited in vitro induced FOXP3 gene transcription (range 70%-90%), whereas Rapa did not inhibit the induction. After clinical heart transplantation the highest FOXP3 mRNA expression levels were measured in biopsies during acute rejection (P=0.03).

CONCLUSIONS

The high FOXP3 mRNA levels during allogeneic responses in vivo and in vitro suggests that regulatory activities of CD25 T cells or the generation of these cells is an intrinsic part of activation. CNI and alphaCD25 mAb in contrast to Rapa, did interfere with this immunosuppressive counter-mechanism and as a result might have an inhibitory effect to tolerance induction after transplantation.

Apoptotic death of infiltrating cells in human cardiac allografts is regulated by IL-2, FASL, and FLIP

INTRODUCTION

In vitro studies have shown that apoptotic cell death is triggered by a IL-2-dependent activation of the Fas-FasL pathway and that this pathway can be inhibited by FLIP.

METHODS

To define whether FLIP regulates apoptotic death of graft infiltrating T-cells during IL-2-mediated rejection, we analyzed endomyocardial biopsies (EMB) from cardiac allograft recipients for CD3, DNA strand breaks (TUNEL assay), FLIP (mRNA and protein), and FasL mRNA expression.

RESULTS

Apoptosis was present in CD3+ T-cell infiltrates. The number of TUNEL-stained mononuclear cells was inversely correlated with FLIP mRNA expression levels (P=.09). FLIP protein was present in 5% to 10% of the infiltrating cells and was constitutively produced by cardiomyocytes irrespective of the rejection grade. Rejection biopsies had elevated IL-2 and FasL mRNA expression levels compared to the expression levels before and after acute rejection (P=.03 and P=.11), while FLIP mRNA expression levels were significantly decreased during rejection (P=.05).

CONCLUSION

Our results indicate that during the IL-2-induced rejection process, infiltrated T cells become more sensitive to apoptosis.

Detection of Cardiac Allograft Rejection and Response to Immunosuppressive Therapy With Peripheral Blood Gene Expression

BACKGROUND

Assessment of gene expression in peripheral blood may provide a noninvasive screening test for allograft rejection. We hypothesized that changes in peripheral blood expression profiles would correlate with biopsy-proven rejection and would resolve after treatment of rejection episodes.

METHODS AND RESULTS

We performed a case-control study nested within a cohort of 189 cardiac transplant patients who had blood samples obtained during endomyocardial biopsy (EMB). Using Affymetrix HU133A microarrays, we analyzed whole-blood expression profiles from 3 groups: (1) control samples with negative EMB (n=7); (2) samples obtained during rejection (at least International Society for Heart and Lung Transplantation grade 3A; n=7); and (3) samples obtained after rejection, after treatment and normalization of the EMB (n=7). We identified 91 transcripts differentially expressed in rejection compared with control (false discovery rate <0.10). In postrejection samples, 98% of transcripts returned toward control levels, displaying an intermediate expression profile for patients with treated rejection (P<0.0001). Cluster analysis of the 40 transcripts with >25% change in expression levels during rejection demonstrated good discrimination between control and rejection samples and verified the intermediate expression profile of postrejection samples. Quantitative real-time polymerase chain reaction confirmed significant differential expression for the predictive markers CFLAR and SOD2 (UniGene ID No. 355724 and No. 384944).

CONCLUSIONS

These data demonstrate that peripheral blood expression profiles correlate with biopsy-proven allograft rejection. Intermediate expression profiles of treated rejection suggest persistent immune activation despite normalization of the EMB. If validated in larger studies, expression profiling may prove to be a more sensitive screening test for allograft rejection than EMB.

Defective inhibition of peripheral CD8+ T cell IL-2 production by anti-calcineurin drugs during acute liver allograft rejection

BACKGROUND

The aim of this study was to evaluate calcineurin activity and interleukin-2 (IL-2) expression by peripheral blood cells as a means of assessing the immune status of liver transplant recipients.

METHODS

Twenty-one patients were studied in a randomized study comparing cyclosporine and tacrolimus as the main immunosuppressive drug. Calcineurin activity was determined after separation of phosphorylated and dephosphorylated products of a calcineurin specific peptide substrate by high performance liquid chromatography(HPLC). Intracellular IL-2 expression was measured by flow cytometry. In 34 additional patients, intracellular IL-2 expression was prospectively measured.

RESULTS

Calcineurin activity fell after transplantation. Values were marginally higher in patients with acute rejection (P=0.059). The percentage of IL-2-producing T cells fell after transplantation. This percentage did not differ between patients with and without rejection. In contrast, the proportion of IL-2-producing CD8+ T cells was higher in patients with acute rejection than in patients free of acute rejection (P=0.003). Moreover, pretransplantation IL-2 expression by CD8+ T cells was higher in patients who subsequently developed acute rejection, suggesting that IL-2 production may be constitutively higher in those patients. The results obtained in the 34 additional patients confirmed these results.

CONCLUSIONS

These data suggest that quantification of intracellular IL-2 in CD8+ T cells may be a useful index of immune status in liver transplant recipients. Preoperative IL-2 levels might serve to individually tailor the immunosuppressive regimen.