Pretransplant identification of acute rejection risk following kidney transplantation

Lack of an accepted definition for 'high immunological risk' hampers individualization of immunosuppressive therapy after kidney transplantation. For recipient-related risk factors for acute rejection, the most compelling evidence points to younger age and African American ethnicity. Recipient gender, body mass, previous transplantation, and concomitant infection or disease do not appear to be influential. Deceased donation now has only a minor effect on rejection risk, but older donor age remains a significant predictor. Conventional immunological markers (human leukocyte antigen [HLA] mismatching, pretransplant anti-HLA alloantibodies, and panel reactive antibodies) are being reassessed in light of growing understanding about the role of donor-specific antibodies (DSA). At the time of transplant, delayed graft function is one of the most clear-cut risk factors for acute rejection. Extended cold ischemia time (≥24 h) may also play a contributory role. While it is not yet possible to establish conclusively the relative contribution of different risk factors for acute rejection after kidney transplantation, the available data point to variables that should be taken into account at the time of transplant. Together, these offer a realistic basis for planning an appropriate immunosuppression regimen in individual patients

TLR9 activation induces normal neutrophil responses in a child with IRAK-4 deficiency: involvement of the direct PI3K pathway.

International audiencePolymorphonuclear neutrophils (PMN) play a key role in innate immunity. Their activation and survival are tightly regulated by microbial products via pattern recognition receptors such as TLRs, which mediate recruitment of the IL-1R-associated kinase (IRAK) complex. We describe a new inherited IRAK-4 deficiency in a child with recurrent pyogenic bacterial infections. Analysis of the IRAK4 gene showed compound heterozygosity with two mutations: a missense mutation in the death domain of the protein (pArg12Cys) associated in cis-with a predicted benign variant (pArg391His); and a splice site mutation in intron 7 that led to the skipping of exon 7. A nontruncated IRAK-4 protein was detected by Western blotting. The patient's functional deficiency of IRAK-4 protein was confirmed by the absence of IRAK-1 phosphorylation after stimulation with all TLR agonists tested. The patient's PMNs showed strongly impaired responses (L-selectin and CD11b expression, oxidative burst, cytokine production, cell survival) to TLR agonists which engage TLR1/2, TLR2/6, TLR4, and TLR7/8; in contrast, the patient's PMN responses to CpG-DNA (TLR9) were normal, except for cytokine production. The surprisingly normal effect of CpG-DNA on PMN functions and apoptosis disappeared after pretreatment with PI3K inhibitors. Together, these results suggest the existence of an IRAK-4-independent TLR9-induced transduction pathway leading to PI3K activation. This alternative pathway may play a key role in PMN control of infections by microorganisms other than pyogenic bacteria in inherited IRAK-4 deficiency

Mutations in STAT3 and IL12RB1 impair the development of human IL-17–producing T cells

The cytokines controlling the development of human interleukin (IL) 17–producing T helper cells in vitro have been difficult to identify. We addressed the question of the development of human IL-17–producing T helper cells in vivo by quantifying the production and secretion of IL-17 by fresh T cells ex vivo, and by T cell blasts expanded in vitro from patients with particular genetic traits affecting transforming growth factor (TGF) β, IL-1, IL-6, or IL-23 responses. Activating mutations in TGFB1, TGFBR1, and TGFBR2 (Camurati-Engelmann disease and Marfan-like syndromes) and loss-of-function mutations in IRAK4 and MYD88 (Mendelian predisposition to pyogenic bacterial infections) had no detectable impact. In contrast, dominant-negative mutations in STAT3 (autosomal-dominant hyperimmunoglobulin E syndrome) and, to a lesser extent, null mutations in IL12B and IL12RB1 (Mendelian susceptibility to mycobacterial diseases) impaired the development of IL-17–producing T cells. These data suggest that IL-12Rβ1– and STAT-3–dependent signals play a key role in the differentiation and/or expansion of human IL-17–producing T cell populations in vivo

Supernatant from Bifidobacterium Differentially Modulates Transduction Signaling Pathways for Biological Functions of Human Dendritic Cells

International audienceBACKGROUND:Probiotic bacteria have been shown to modulate immune responses and could have therapeutic effects in allergic and inflammatory disorders. However, the signaling pathways engaged by probiotics are poorly understood. We have previously reported that a fermentation product from Bifidobacterium breve C50 (BbC50sn) could induce maturation, high IL-10 production and prolonged survival of DCs via a TLR2 pathway. We therefore studied the roles of mitogen-activated protein kinases (MAPK), glycogen synthase kinase-3 (GSK3) and phosphatidylinositol 3-kinase (PI3K) pathways on biological functions of human monocyte-derived DCs treated with BbC50sn.METHODOLOGY/PRINCIPAL FINDINGS:DCs were differentiated from human monocytes with IL-4 and GM-CSF for 5 days and cultured with BbC50sn, lipopolysaccharide (LPS) or Zymosan, with or without specific inhibitors of p38MAPK (SB203580), ERK (PD98059), PI3K (LY294002) and GSK3 (SB216763). We found that 1) the PI3K pathway was positively involved in the prolonged DC survival induced by BbC50sn, LPS and Zymosan in contrast to p38MAPK and GSK3 which negatively regulated DC survival; 2) p38MAPK and PI3K were positively involved in DC maturation, in contrast to ERK and GSK3 which negatively regulated DC maturation; 3) ERK and PI3K were positively involved in DC-IL-10 production, in contrast to GSK3 that was positively involved in DC-IL-12 production whereas p38MAPK was positively involved in both; 4) BbC50sn induced a PI3K/Akt phosphorylation similar to Zymosan and a p38MAPK phosphorylation similar to LPS.CONCLUSION/SIGNIFICANCE:We report for the first time that a fermentation product of a bifidobacteria can differentially activate MAPK, GSK3 and PI3K in order to modulate DC biological functions. These results give new insights on the fine-tuned balance between the maintenance of normal mucosal homeostasis to commensal and probiotic bacteria and the specific inflammatory immune responses to pathogen bacteria

ADHERE: randomized controlled trial comparing renal function in de novo kidney transplant recipients receiving prolonged-release tacrolimus plus mycophenolate mofetil or sirolimus

ADHERE was a randomized, open-label, Phase IV study comparing renal function at Week 52 postkidney transplant, in patients who received prolongedrelease tacrolimus-based immunosuppressive regimens. On Days 0?27, patients received prolonged-release tacrolimus (initially 0.2 mg/kg/day), corticosteroids, and mycophenolate mofetil (MMF). Patients were randomized on Day 28 to receive either prolonged-release tacrolimus plus MMF (Arm 1) or prolongedrelease tacrolimus (?25% dose reduction on Day 42) plus sirolimus (Arm 2). The primary endpoint was glomerular filtration rate by iohexol clearance (mGFR) at Week 52. Secondary endpoints included eGFR, creatinine clearance (CrCl), efficacy failure (patient withdrawal or graft loss), and patient/graft survival. Tolerability was analyzed. The full-analysis set comprised 569 patients (Arm 1: 287; Arm 2: 282). Week 52 mean mGFR was similar in Arm 1 versus Arm 2 (40.73 vs. 41.75 ml/min/1.73 m2; P = 0.405), as were the secondary endpoints, except composite efficacy failure, which was higher in Arm 2 versus 1 (18.2% vs. 11.5%; P = 0.002) owing to a higher postrandomization withdrawal rate due to adverse events (AEs) (14.4% vs. 5.2%). Results from this study show comparable renal function between arms at Week 52, with fewer AEs leading to study discontinuation with prolonged-release tacrolimus plus MMF (Arm 1) versus lower dose prolonged-release tacrolimus plus sirolimus (Arm 2)

Mutations in STAT3 and IL12RB1 impair the development of human IL-17 producing T cells

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Rôle de l'interaction Fas/FasL dans le rejet de greffe (apoptose des lymphocytes T alloréactifs induite par des cellules endothéliales exprimant FasL et étude du polymorphisme du gène FAS chez les transplantés rénaux)

Une des alternatives visant à induire une tolérance spécifique vis-à-vis du greffon plutôt qu'une dépression globale du système immunitaire du receveur serait l'induction d'une apoptose par la voie Fas/FasL des lymphocytes T alloréactifs. Nous avons transfecté une lignée de cellule endothéliale humaine avec l'ADNc du ligand de Fas humain et avons montré que ces cellules pouvaient non seulement induire l'apoptose de lymphocytes T activés mais également inhibaient la prolife ration lymphocytaire in vitro par la voie Fas/FasL. L'utilisation de l'endothélium du greffon pourrait donc être un outil intéressant pour transmettre un signal de mort aux lymphocytes alloréactifs et induire ainsi un état de tolérance au cours de la greffe. L'apoptose par la voie Fas/FasL étant impliquée à la fois dans la régulation de la réponse immune et dans les cellules tubulaires rénales au cours du rejet aigu, nous avons étudié le polymorphisme de Fas chez les receveurs transplantés rénaux ainsi que chez les donneurs. Aucune corrélation n'a été mise en évidence entre la survenue d'un rejet aigu cellulaire et le polymorphisme de Fas du receveur. En revanche, l'étude cas-témoin réalisée chez les donneurs a montré que le génotype homozygote GG était significativement plus important chez les patients n'ayant pas fait d'épisode de rejet. Le polymorphisme du gène Fas du donneur serait donc impliqué de façon directe ou indirecte dans les phénomènes de rejet et le phénotype homozygote GG serait protecteur contre le rejet aigu cellulaire.TOURS-BU Médecine (372612103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Effet de l'acide mycophénolique sur les voies de signalisation activées par des agents pro-inflammatoires dans la cellule dendritique humaine

Initialement développés pour leur action inhibitrice sur les lymphocytes T, les immunosuppresseurs affectent aussi les cellules dendritiques (CD). Nous avons précédemment montré que l acide mycophénolique (MPA) induisait une résistance des CD humaines à la maturation, néanmoins son mécanisme d action sur les CD reste méconnu. Ce travail de thèse montre que le MPA inhibe l activation de p38MAPK et que cette propriété entraîne l inhibition de la maturation phénotypique induite par le facteur nécrotique tumoral a (TNFa), la diminution de la sécrétion de cytokines pro-inflammatoires et de la capacité allostimulatrice induite par le TNFa ou le lipopolysaccharide suggérant que l inhibition de la synthèse de cytokines inflammatoires serait déterminante pour inhiber la capacité allostimulatrice. Nous rapportons également que le MPA inhibe la phosphorylation de ERK induite par le TNFa. Ainsi, l action du MPA sur les CD s exerce différemment selon l environnement dans lequel se trouvent les CD.TOURS-BU Médecine (372612103) / SudocSudocFranceAustraliaFRA

Antigènes microbiens et transduction par les voies Toll (implications dans la biologie des cellules dendritiques)

Les cellules dendritiques (DC) constituent une population hétérogène qui fait le lien entre immunité innée et adaptative. Les DC possèdent des Toll like récepteurs (TLR) qui reconnaissent un large spectre de structures microbiennes conservées. Selon le type d exposition bactérienne, le recrutement des TLR et les signaux de transduction induits, le processus de maturation de la DC va conditionner une différenciation lymphocytaire spécifique. Nous avons mis en évidence que le surnageant d une bifidobactérie (BBC50SN) induit une maturation et une survie prolonge e des DC, avec une forte production d IL-10 et une faible production d IL-12. En utilisant des inhibiteurs chimiques, nous avons pu mettre en évidence que le BBC50SN induit des signaux de transduction complexes impliquant NF-KB mais également les mapkinases et la pi3kinase. L étude d un cas de déficit en irak4 a mis en évidence, au niveau des polynucléaires neutrophiles, une voie TLR9 indépendante de irak4 impliquant la pi3k.Dendritic cells (DCs) are heterogenous population which constitute a link between innate and adaptative immunity. DCs express Toll like receptors (TLRs) which recognize large bacterial conserved components. Depending of the bacterial contact, the TLR engagement and the transduction pathway involved, the process of DCs maturation induces the specificity of lymphocyte differentiation. We have described that the supernatant of a bifidobacteria (Bbc50SN) induced DC maturation and a prolonged DC survival with a high IL-10 synthesis and a low IL-12 production. Using chemical inhibitors, we showed that BbC50SN induced complex transduction pathway including NF-kB but also mapkinases and Pi3kinase. Moreover, the study of a case of irak4 deficiency revealed, on neutrophil, a TLR9 pathway independent of irak4 and but dependent of pi3k.TOURS-BU Médecine (372612103) / SudocSudocFranceF