Design, cohort profile and comparison of the KTD-Innov study: a prospective multidimensional biomarker validation study in kidney allograft rejection.

There is an unmet need for robust and clinically validated biomarkers of kidney allograft rejection. Here we present the KTD-Innov study (ClinicalTrials.gov, NCT03582436), an unselected deeply phenotyped cohort of kidney transplant recipients with a holistic approach to validate the clinical utility of precision diagnostic biomarkers. In 2018-2019, we prospectively enrolled consecutive adult patients who received a kidney allograft at seven French centers and followed them for a year. We performed multimodal phenotyping at follow-up visits, by collecting clinical, biological, immunological, and histological parameters, and analyzing a panel of 147 blood, urinary and kidney tissue biomarkers. The primary outcome was allograft rejection, assessed at each visit according to the international Banff 2019 classification. We evaluated the representativeness of participants by comparing them with patients from French, European, and American transplant programs transplanted during the same period. A total of 733 kidney transplant recipients (64.1% male and 35.9% female) were included during the study. The median follow-up after transplantation was 12.3 months (interquartile range, 11.9-13.1 months). The cumulative incidence of rejection was 9.7% at one year post-transplant. We developed a distributed and secured data repository in compliance with the general data protection regulation. We established a multimodal biomarker biobank of 16,736 samples, including 9331 blood, 4425 urinary and 2980 kidney tissue samples, managed and secured in a collaborative network involving 7 clinical centers, 4 analytical platforms and 2 industrial partners. Patients' characteristics, immune profiles and treatments closely resembled those of 41,238 French, European and American kidney transplant recipients. The KTD-Innov study is a unique holistic and multidimensional biomarker validation cohort of kidney transplant recipients representative of the real-world transplant population. Future findings from this cohort are likely to be robust and generalizable.

Validation of the clinical utility of microRNA as noninvasive biomarkers of cardiac allograft rejection: A prospective longitudinal multicenter study.

While studies have shown an association between microRNAs and cardiac rejection, the clinical relevance of a preidentified miRNA signature as a noninvasive biomarker has never been assessed in prospective multicentric unselected cohorts. To address this unmet need, we designed a prospective study (NCT02672683) including recipients from 11 centers between August 2016 to March 2018. The objective was to validate the association between 3 previously identified circulating microRNA (10a, 92a, 155) and the histopathological diagnosis of rejection. Both relative and absolute (sensitivity analysis) quantifications of microRNAs were performed. Overall, 461 patients were included (831 biopsies, 79 rejections). A per-protocol interim analysis (258 biopsies, 49 rejections) did not find any association between microRNA and rejection (microRNA 10a: odds ratio (OR) = 1.05, 95% confidence intervals (CI) = 0.87-1.27, p = 0.61; 92a: OR = 0.98, 95%CI = 0.87-1.10, p = 0.68; 155: OR = 0.91, 95%CI = 0.76-1.10, p = 0.33). These results were confirmed in the sensitivity analysis. The analysis of the remaining sera was stopped for futility. This study shows no clinical utility of circulating microRNAs 10a, 92a, and 155 monitoring in heart allograft recipients.

Correlation Between Microvascular Inflammation in Endomyocardial Biopsies and Rejection Transcripts, Donor-specific Antibodies, and Graft Dysfunction in Antibody-mediated Rejection.

BACKGROUND: The pathology-based diagnosis of cardiac antibody-mediated rejection (AMR) relies on the 2013 International Society for Heart and Lung Transplantation Working Formulation, in which microvascular inflammation (MVI) is considered as present or absent regardless of its extent. This work assessed the biological and clinical value of a semiquantitative evaluation of the extent of MVI in endomyocardial biopsies (EMBs). METHODS: We retrospectively graded the extent of MVI in 291 EMB from 291 patients according to a 4-point scale in which MVI scores of 0, 1, 2, and 3 represented 0%, 1%-10%, 11%-50%, and >50% of the myocardial area, respectively. We analyzed the association between the MVI score and tissue rejection molecular activity assessed by microarrays or reverse transcriptase multiplex ligation-dependent probe amplification, current pathology classification (pathologic AMR [pAMR]), anti-HLA donor-specific antibodies, and graft dysfunction. RESULTS: Overall, 172 (59.1%), 33 (11.4%), 42 (14.4%), and 44 (15.1%) EMB were given MVI scores of 0, 1, 2, and 3, respectively. pAMR1(H+) and pAMR2/3 categories were found to be heterogeneous in terms of MVI score. Acute cellular rejection grades did not influence the MVI score. In both molecular approaches, we observed a stepwise increase in the expression of AMR-related transcripts with increasing MVI scores, independent of the C4d or CD68 status (P < 0.001). Both the frequency and mean fluorescence intensity of donor-specific antibodies gradually increased with the MVI score (P < 0.001). Acute graft dysfunction was more frequent in MVI score 3 (P < 0.001). CONCLUSIONS: The intensity of MVI in EMB, based on a semiquantitative evaluation of its extent, has biological and clinical importance.

Identification and Characterization of Trajectories of Cardiac Allograft Vasculopathy After Heart Transplantation: A Population-Based Study.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient mortality. Little is known about the prototypes of CAV trajectories at the population level. We aimed to identify the different evolutionary profiles of CAV and to determine the respective contribution of immune and nonimmune factors in CAV development. METHODS: Heart transplant recipients were from 4 academic centers (Pitié-Salpêtrière and Georges Pompidou Hospital, Paris, Katholieke Universiteit Leuven, and Cedars-Sinai, Los Angeles; 2004-2016). Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessments of clinical, histological, and immunologic parameters. The main outcome was a prediction for CAV trajectory. We identified CAV trajectories by using unsupervised latent class mixed models. We then identified the independent predictive variables of the CAV trajectories and their association with mortality. RESULTS: A total of 1301 patients were included (815 and 486 in the European and US cohorts, respectively). The median follow-up after transplantation was 6.6 (interquartile range, 4-9.1) years with 4710 coronary angiographies analyzed. We identified 4 distinct profiles of CAV trajectories over 10 years. The 4 trajectories were characterized by (1) patients without CAV at 1 year and nonprogression over time (56.3%), (2) patients without CAV at 1 year and late-onset slow CAV progression (7.6%), (3) patients with mild CAV at 1 year and mild progression over time (23.1%), and (4) patients with mild CAV at 1 year and accelerated progression (13.0%). This model showed good discrimination (0.92). Among candidate predictors assessed, 6 early independent predictors of these trajectories were identified: donor age (P<0.001), donor male sex (P<0.001), donor tobacco consumption (P=0.001), recipient dyslipidemia (P=0.009), class II anti-human leukocyte antigen donor-specific antibodies (P=0.004), and acute cellular rejection ≥2R (P=0.028). The 4 CAV trajectories manifested consistently in the US independent cohort with similar discrimination (0.97) and in different clinical scenarios, and showed gradients for overall-cause mortality (P<0.001). CONCLUSIONS: In a large multicenter and highly phenotyped prospective cohort of heart transplant recipients, we identified 4 CAV trajectories and their respective independent predictive variables. Our results provide the basis for a trajectory-based assessment of patients undergoing heart transplantation for early risk stratification, patient monitoring, and clinical trials. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04117152.

Missing self triggers NK cell-mediated chronic vascular rejection of solid organ transplants.

Current doctrine is that microvascular inflammation (MVI) triggered by a transplant -recipient antibody response against alloantigens (antibody-mediated rejection) is the main cause of graft failure. Here, we show that histological lesions are not mediated by antibodies in approximately half the participants in a cohort of 129 renal recipients with MVI on graft biopsy. Genetic analysis of these patients shows a higher prevalence of mismatches between donor HLA I and recipient inhibitory killer cell immunoglobulin-like receptors (KIRs). Human in vitro models and transplantation of ß2-microglobulin-deficient hearts into wild-type mice demonstrates that the inability of graft endothelial cells to provide HLA I-mediated inhibitory signals to recipient circulating NK cells triggers their activation, which in turn promotes endothelial damage. Missing self-induced NK cell activation is mTORC1-dependent and the mTOR inhibitor rapamycin can prevent the development of this type of chronic vascular rejection.

[Multidimensional approaches for risk stratification in transplantation]. / Approches multidimensionnelles pour la stratification du risque en transplantation.

Despite considerable progress in the short-term outcomes of renal transplantation, there has been little improvement over the last 15years on long-term survival. The main limitation is the lack of precise knowledge of the determinants of renal allograft loss and robust prognostic systems providing an individual prediction. Kidney transplantation must address a pressing clinical need to accurately define the determinants of kidney renal allograft survival in order to improve risk stratification. To achieve this goal, four steps need to be considered in the development of prognostic tools: the characterization and identification of the phenotype of the pathology, the assessment of prognostic factors of the event of interest in the population, the assessment of the additional value provided by a newly identified prognostic factor to conventional factors already known in clinical practice as well as the construction of prognostic tools, on the basis of multidimensional integrative models allowing a precise stratification of the risk, at individual and population scale.

Antibody-mediated rejection in pediatric small bowel transplantation: Capillaritis is a major determinant of C4d positivity in intestinal transplant biopsies.

The diagnostic criteria for antibody-mediated rejection (ABMR) after small bowel transplantation (SBT) are not clearly defined, although the presence of donor-specific antibodies (DSAs) has been reported to be deleterious for graft survival. We aimed to determine the incidence and prognostic value of DSAs and C4d in pediatric SBT and to identify the histopathologic features associated with C4d positivity. We studied all intestinal biopsies (IBx) obtained in the first year posttransplantation (N = 345) in a prospective cohort of 23 children. DSAs and their capacity to fix C1q were identified by using Luminex technology. Eighteen patients (78%) had DSAs, and 9 had the capacity to fix C1q. Seventy-eight IBx (22.6%) were C4d positive. The independent determinants of C4d positivity were capillaritis grades 2 and 3 (odds ratio [OR] 4.02, P = .047 and OR 5.17, P = .003, respectively), mucosal erosion/ulceration (OR 2.8, P = .019), lamina propria inflammation grades 1 and 2/3 (OR 1.95, P = .043 and OR 3.1, P = .016, respectively), and chorion edema (OR 2.16, P = .028). Complement-fixing DSAs and repeated C4d-positive IBx were associated with poor outcome (P = .021 and P = .001, respectively). Our results support that capillaritis should be considered as a feature of ABMR in SBT and identify C1q-fixing DSAs and repeated C4d positivity as potential markers of poor outcome.

Endothelial chimerism and vascular sequestration protect pancreatic islet grafts from antibody-mediated rejection.

Humoral rejection is the most common cause of solid organ transplant failure. Here, we evaluated a cohort of 49 patients who were successfully grafted with allogenic islets and determined that the appearance of donor-specific anti-HLA antibodies (DSAs) did not accelerate the rate of islet graft attrition, suggesting resistance to humoral rejection. Murine DSAs bound to allogeneic targets expressed by islet cells and induced their destruction in vitro; however, passive transfer of the same DSAs did not affect islet graft survival in murine models. Live imaging revealed that DSAs were sequestrated in the circulation of the recipients and failed to reach the endocrine cells of grafted islets. We used murine heart transplantation models to confirm that endothelial cells were the only accessible targets for DSAs, which induced the development of typical microvascular lesions in allogeneic transplants. In contrast, the vasculature of DSA-exposed allogeneic islet grafts was devoid of lesions because sprouting of recipient capillaries reestablished blood flow in grafted islets. Thus, we conclude that endothelial chimerism combined with vascular sequestration of DSAs protects islet grafts from humoral rejection. The reduced immunoglobulin concentrations in the interstitial tissue, confirmed in patients, may have important implications for biotherapies such as vaccines and monoclonal antibodies.

Relatedness of Antibodies to Peptides Containing Homocitrulline or Citrulline in Patients with Rheumatoid Arthritis.

OBJECTIVE: Antibodies that target citrullinated protein/peptide (ACPA) and homocitrullinated/carbamylated protein/peptide (AHCPA) are associated with rheumatoid arthritis (RA). The relationship between ACPA and AHCPA remains unclear. We examined the expression and cross-reactivity of these antibodies using citrulline- and homocitrulline-containing synthetic peptides, CitJED and HomoCitJED, respectively, which have equal numbers of citrulline or homocitrulline residues on the same peptide backbone. METHODS: Serum from healthy subjects (n = 51) and patients with RA (n = 137), systemic lupus erythematosus (SLE; n = 37), and psoriatic arthritis (PsA; n = 37) were screened for IgG anti-CitJED and anti-HomoCitJED antibodies by ELISA. Cross-reactivity of these antibodies was examined by inhibition with various concentrations of CitJED and HomoCitJED. RESULTS: Out of 137 patients with RA, antibodies to CitJED and HomoCitJED were detected in 69 (50%) and 78 (57%), respectively. Anti-CitJED and HomoCitJED antibodies were 77% concordant and their levels were strongly correlated [Spearman correlation coefficient (rs) = 0.6676]. Sera from 25/27 patients (93%) with RA were inhibited by both CitJED and HomoCitJED with equal or higher affinity for the cognate (homologous) peptide. CONCLUSION: Antibodies to CitJED and HomoCitJED frequently occurred in RA, but were not found in SLE or PsA, suggesting that these antibodies are specific to RA. Cross-reactivity between anti-HomoCitJED and anti-CitJED antibodies suggests that ACPA and AHCPA are derived from the same B cell population and both may contribute to the pathogenesis of RA.

Gene Expression Profiling for the Identification and Classification of Antibody-Mediated Heart Rejection.

BACKGROUND: Antibody-mediated rejection (AMR) contributes to heart allograft loss. However, an important knowledge gap remains in terms of the pathophysiology of AMR and how detection of immune activity, injury degree, and stage could be improved by intragraft gene expression profiling. METHODS: We prospectively monitored 617 heart transplant recipients referred from 4 French transplant centers (January 1, 2006-January 1, 2011) for AMR. We compared patients with AMR (n=55) with a matched control group of 55 patients without AMR. We characterized all patients using histopathology (ISHLT [International Society for Heart and Lung Transplantation] 2013 grades), immunostaining, and circulating anti-HLA donor-specific antibodies at the time of biopsy, together with systematic gene expression assessments of the allograft tissue, using microarrays. Effector cells were evaluated with in vitro human cell cultures. We studied a validation cohort of 98 heart recipients transplanted in Edmonton, AB, Canada, including 27 cases of AMR and 71 controls. RESULTS: A total of 240 heart transplant endomyocardial biopsies were assessed. AMR showed a distinct pattern of injury characterized by endothelial activation with microcirculatory inflammation by monocytes/macrophages and natural killer (NK) cells. We also observed selective changes in endothelial/angiogenesis and NK cell transcripts, including CD16A signaling and interferon-γ-inducible genes. The AMR-selective gene sets accurately discriminated patients with AMR from those without and included NK transcripts (area under the curve=0.87), endothelial activation transcripts (area under the curve=0.80), macrophage transcripts (area under the curve=0.86), and interferon-γ transcripts (area under the curve=0.84; P<0.0001 for all comparisons). These 4 gene sets showed increased expression with increasing pathological AMR (pAMR) International Society for Heart and Lung Transplantation grade (P<0.001) and association with donor-specific antibody levels. The unsupervised principal components analysis demonstrated a high proportion of molecularly inactive pAMR1(I+), and there was significant molecular overlap between pAMR1(H+) and full-blown pAMR2/3 cases. Endothelial activation transcripts, interferon-γ, and NK transcripts showed association with chronic allograft vasculopathy. The molecular architecture and selective AMR transcripts, together with gene set discrimination capacity for AMR identified in the discovery set, were reproduced in the validation cohort. CONCLUSIONS: Tissue-based measurements of specific pathogenesis-based transcripts reflecting NK burden, endothelial activation, macrophage burden, and interferon-γ effects accurately classify AMR and correlate with degree of injury and disease activity. This study illustrates the clinical potential of a tissue-based analysis of gene transcripts to refine diagnosis of heart transplant rejection.

Antihomocitrullinated fibrinogen antibodies are specific to rheumatoid arthritis and frequently bind citrullinated proteins/peptides.

OBJECTIVE: Anticitrullinated protein/peptide antibodies (ACPA) are implicated in rheumatoid arthritis (RA) pathogenesis and linked to the shared epitope (SE). Citrulline modification is very similar to a different modified amino acid, homocitrulline. We investigated antihomocitrullinated protein/ peptide antibody (AHCPA) specificity for RA, whether ACPA were also able to bind homocitrullinated targets, and whether the SE could accommodate homocitrullinated peptide. METHODS: Homocitrullinated fibrinogen was used to screen sera from patients with RA, psoriatic arthritis, and systemic lupus erythematosus, and healthy subjects for AHCPA using ELISA. Homocitrullination sites on fibrinogen were identified by mass spectrometry. ACPA were affinity-purified using a synthetic citrullinated peptide and tested for binding to homocitrullinated protein/peptide. Inhibition of antihomocitrullinated fibrinogen antibody binding was examined. Homocitrullinated peptide interaction with the SE was studied using computer modeling. RESULTS: IgG antihomocitrullinated fibrinogen antibodies were found specifically in 49% of patients with RA. Enrichment of ACPA by affinity purification from 5 patients with RA also enriched AHCPA. Serum AHCPA was inhibited by citrullinated fibrinogen and more significantly by homocitrullinated fibrinogen. Computer modeling indicated that the SE could accommodate a homocitrullinated peptide without steric hindrance. Mass spectrometry identified that 89/103 lysines of fibrinogen could be homocitrullinated, and 5 peptides that could be both citrullinated and homocitrullinated and are predicted to bind the SE. CONCLUSION: Antihomocitrullinated fibrinogen antibodies are specific to RA. The presence of AHCPA coincides with ACPA, and AHCPA copurifies with ACPA in affinity purification and is inhibited by citrullinated and homocitrullinated antigens. Thus AHCPA and ACPA are frequently cross-reactive and homocitrullinated proteins/peptides may bind the SE.

Anti-citrullinated protein antibodies in unaffected first-degree relatives of rheumatoid arthritis patients.

OBJECTIVE: First-degree relatives (FDRs) of rheumatoid arthritis (RA) patients sharing genetic and environmental risk factors for RA may represent a pre-RA state. Since anti-cyclic citrullinated protein/peptide antibodies (ACPAs) appear years before the onset of RA, the purpose of this study was to determine the prevalence of various ACPAs in FDRs of RA patients. METHODS: We evaluated 88 RA patients, 50 unaffected FDRs, and 20 healthy control subjects. Six different types of ACPAs were determined by enzyme-linked immunosorbent assay. Joint and periodontal disease symptoms were self-reported. Patients and FDRs were HLA typed for the shared epitope (SE) and the RA-protective alleles HLA-DRB*1301/1302. RESULTS: FDRs had a high prevalence of ACPAs (48%) as compared to controls (10%). Prevalence of the SE and smoking in FDRs was also high (62% and 49%, respectively). Of all of the ACPAs in the FDRs, 13 of 32 (41%) were of the IgA isotype. The most commonly expressed IgG ACPA targeted citrullinated vimentin, occurring in 20% of FDRs. The FDRs had an average of 1 type of ACPA, whereas the RA patients expressed a median of 5 different ACPAs. The only FDR to later develop RA expressed 4 different ACPAs. Joint and periodontal disease symptoms in the FDRs were significantly associated with smoking (OR 5.714 [95% confidence interval (95% CI) 1.151-28.3] and OR 12.25 [95% CI 2.544-58.99], respectively), but not with ACPAs. CONCLUSION: The rate of ACPA positivity in unaffected FDRs of RA patients with a high prevalence of the SE and smoking was 48%, whereas ACPAs were rare in the healthy controls. ACPAs in the FDRs of RA patients was most commonly of the IgA isotype, but IgG ACPA targeting citrullinated vimentin was also frequently found.

The involvement of SMILE/TMTC3 in endoplasmic reticulum stress response.

BACKGROUND: The state of operational tolerance has been detected sporadically in some renal transplanted patients that stopped immunosuppressive drugs, demonstrating that allograft tolerance might exist in humans. Several years ago, a study by Brouard et al. identified a molecular signature of several genes that were significantly differentially expressed in the blood of such patients compared with patients with other clinical situations. The aim of the present study is to analyze the role of one of these molecules over-expressed in the blood of operationally tolerant patients, SMILE or TMTC3, a protein whose function is still unknown. METHODOLOGY/PRINCIPAL FINDINGS: We first confirmed that SMILE mRNA is differentially expressed in the blood of operationally tolerant patients with drug-free long term graft function compared to stable and rejecting patients. Using a yeast two-hybrid approach and a colocalization study by confocal microscopy we furthermore report an interaction of SMILE with PDIA3, a molecule resident in the endoplasmic reticulum (ER). In accordance with this observation, SMILE silencing in HeLa cells correlated with the modulation of several transcripts involved in proteolysis and a decrease in proteasome activity. Finally, SMILE silencing increased HeLa cell sensitivity to the proteasome inhibitor Bortezomib, a drug that induces ER stress via protein overload, and increased transcript expression of a stress response protein, XBP-1, in HeLa cells and keratinocytes. CONCLUSION/SIGNIFICANCE: In this study we showed that SMILE is involved in the endoplasmic reticulum stress response, by modulating proteasome activity and XBP-1 transcript expression. This function of SMILE may influence immune cell behavior in the context of transplantation, and the analysis of endoplasmic reticulum stress in transplantation may reveal new pathways of regulation in long-term graft acceptance thereby increasing our understanding of tolerance.

What can we learn from the transcriptional characterization of spontaneously tolerant transplant recipients?

PURPOSE OF REVIEW: Even if improvements of immunosuppressive treatments enabled to prevent acute rejection in solid organ transplantation, current immunosuppressive regimens are implicated in long-term side effects without the resolution of chronic rejection. Thus, during last years, research focused mainly on immunosuppression weaning off studies based on individualized follow-up of patients. Beyond animal models, studies have been emphasized by descriptions of a particular group of transplant patients displaying an operational tolerance in the absence of immunosuppressive treatments. Herein we will review recent advances in transcriptional characterization of spontaneously tolerant transplant recipients. RECENT FINDINGS: Transcriptomic profiling in the blood of these so-called 'operationally tolerant' patients succeeded to establish tolerance footprint that could be used to detect a tolerance profile among transplanted patients under immunosuppression, in order to adapt their treatment and eventually wean off them. SUMMARY: The advent of this field raise questions about how to blend and cross transcriptomic studies in the different areas of transplantation, how to use such set of genes to have a clear view of the graft status at a given time and what will be their contributions.

Patients with drug-free long-term graft function display increased numbers of peripheral B cells with a memory and inhibitory phenotype.

Several transplant patients maintain stable kidney graft function in the absence of immunosuppression. Here we compared the characteristics of their peripheral B cells to that of others who had stable graft function but were under pharmacologic immunosuppression, to patients with chronic rejection and to healthy volunteers. In drug-free long-term graft function (DF) there was a significant increase in both absolute cell number and frequency of total B cells; particularly activated, memory and early memory B cells. These increased B-cell numbers were associated with a significantly enriched transcriptional B-cell profile. Costimulatory/migratory molecules (B7-2/CD80, CD40, and CD62L) were upregulated in B cells; particularly in memory CD19(+)IgD(-)CD38(+/-)CD27(+) B cells in these patients. Their purified B cells, however, responded normally to a polyclonal stimulation and did not have cytokine polarization. This phenotype was associated with the following specific characteristics which include an inhibitory signal (decreased FcgammaRIIA/FcgammaRIIB ratio); a preventive signal of hyperactive B-cell response (an increase in BANK1, which negatively modulates CD40-mediated AKT activation); an increased number of B cells expressing CD1d and CD5; an increased BAFF-R/BAFF ratio that could explain why these patients have more peripheral B cells; and a specific autoantibody profile. Thus, our findings show that patients with DF have a particular blood B-cell phenotype that may contribute to the maintenance of long-term graft function.

Immunoproteasome beta subunit 10 is increased in chronic antibody-mediated rejection.

Chronic active antibody-mediated rejection is a form of late rejection with a poor prognosis. To identify specific markers of this, we analyzed several microarray studies in the literature and performed mRNA profiling of 65 biopsies and 165 blood samples of a large cohort of renal transplant patients with precisely characterized pathologies. Immunoproteasome beta subunit 10 was found to be specifically increased in the graft and blood samples during chronic active antibody-mediated rejection and was also significantly increased in rat cardiac allografts undergoing acute rejection as well as chronic active antibody-mediated rejection. This syndrome is characterized by chronic transplant vasculopathy associated with diffuse C4d staining and circulating donor-specific antibodies. Using this animal model, we found that administration of the proteasome inhibitor, Bortezomib, delayed acute rejection and attenuated the humoral response in both the acute phase and established state of this syndrome in a dose-dependent manner. Following treatment with this reagent, donor-specific antibodies and C4d deposition were reduced. These studies highlight the role of the proteasome in chronic rejection and identify this molecule as a marker of this syndrome.

Interleukin 7 receptor alpha as a potential therapeutic target in transplantation.

Drugs targeting memory lymphocytes may allow for a better control of rejection in transplantation, particularly in immunized patients. In this article the rationale of targeting interleukin 7 receptor alpha (IL-7Ralpha), a molecule expressed by both memory and naive T cells, is reviewed in the context of transplantation. Whereas naive T cells are partly responsible for acute rejection and are targeted by current immunosuppressive drugs that block costimulatory signals (cyclosporine A, anti-CD3 antibody, anti-CD52 antibody, anti-thymocyte globulin, etc.), memory T cells are resistant to costimulation blockade. As such, memory cells are an obstacle to experimental tolerance induction and may be involved in chronic rejection. There is thus much scientific interest in developing molecules able to target these cells. The role of the IL-7/IL-7Ralpha pathway in transplantation rejection has been suggested by the effect of an anti-IL-7 monoclonal antibody which, when associated with costimulation blockade, prolonged heart allograft survival in mice. Here the hypothesis that targeting IL-7Ralpha would preserve effector T cells that are less dependent on IL-7 for survival while sparing regulatory CD4+ CD25high IL-7Ralpha(low) T cells is discussed. An anti-IL-7Ralpha antibody could also help achieve allograft tolerance by reducing alloreactive cells.

Variation in numbers of CD4+CD25highFOXP3+ T cells with normal immuno-regulatory properties in long-term graft outcome.

Chronic rejection (CR) is a major cause of long-term graft loss that would be avoided by the induction of tolerance. We previously showed that renal transplant patients with CR have lower numbers of peripheral CD4(+)CD25(high) T cells than operationally tolerant patients, patients with stable graft function and healthy volunteers (HV). We explored here the profile of CD4(+)CD25(high) blood T cells in these patients focusing on their expression of the regulatory T cells (Treg) gene Forkhead Box P3 (FOXP3) and their suppressive function. We show that CR is associated with a decreased number of CD4(+)CD25(high)FOXP3(+)T cells with normal regulatory profile, whereas graft acceptance is associated with CD4(+)CD25(high)FOXP3(+)T cell numbers similar to HVs. These data suggest that Treg numbers, rather than their intrinsic suppressive capacity, may contribute to determining the long-term fate of renal transplants.