Stimulation des lymphocytes T régulateurs chez la souris (implications dans la physiopathologie et la thérapie du diabète auto-immun)

Les lymphocytes T régulateurs CD4+CD25+FoxP3+ (Treg) sont des acteurs majeurs de la régulation des réponses immunes. Mon travail de thèse s est porté sur l étude de l impact de la stimulation des Treg dans le diabète auto-immun chez la souris. Dans un premier temps, nous avons étudié l impact de l activation des lymphocytes T conventionnels (Tconv) sur l homéostasie des Treg. Dans un modèle de diabète auto-immun, le transfert de Tconv spécifiques d un antigène pancréatique augmente fortement l expansion et la fonction suppressive des Treg dans le pancréas et les ganglions drainant, induisant une prévention de la maladie à long terme. De façon surprenante, ce boost des Treg est indépendant de l IL-2 mais partiellement dépendant du TNF. Dans un contexte de réponse immune inflammatoire contre un antigène exogène, l activation des Tconv augmente aussi l expansion des Treg; cet effet boost est cette fois dépendant de l IL-2. Dans un deuxième temps, nous avons montré que l injection d IL-2 pendant 5 jours induit une rémission des signes cliniques de diabète chez la souris NOD. Le traitement induit l augmentation du nombre de Treg et une modification de leur phénotype, ainsi qu une diminution de la sécrétion d IFN-gamma par les Tconv du pancréas, pouvant expliquer son effet curatif. Enfin, une analyse de transcriptome montre que l IL-2 modifie l expression de nombreux gènes chez les Treg, alors que son effet sur les Tconv est faible. Cette étude met en évidence un nouveau mécanisme de rétrocontrôle de la réponse immune via un boost des Treg par les Tconv. De plus, nous montrons un effet curatif de l administration d IL-2 dans le diabète par action sur les Treg du pancréas.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

The Alternative NF-κB Pathway in Regulatory T Cell Homeostasis and Suppressive Function

CD4+Foxp3+ regulatory T cells (Tregs) are essential regulators of immune responses. Perturbation of Treg homeostasis or function can lead to uncontrolled inflammation and autoimmunity. Therefore, understanding the molecular mechanisms involved in Treg biology remains an active area of investigation. It has been shown previously that the NF-κB family of transcription factors, in particular, the canonical pathway subunits, c-Rel and p65, are crucial for the development, maintenance, and function of Tregs. However, the role of the alternative NF-κB pathway components, p100 and RelB, in Treg biology remains unclear. In this article, we show that conditional deletion of the p100 gene, nfkb2, in Tregs, resulted in massive inflammation because of impaired suppressive function of nfkb2-deficient Tregs. Surprisingly, mice lacking RelB in Tregs did not exhibit the same phenotype. Instead, deletion of both relb and nfkb2 rescued the inflammatory phenotype, demonstrating an essential role for p100 as an inhibitor of RelB in Tregs. Our data therefore illustrate a new role for the alternative NF-κB signaling pathway in Tregs that has implications for the understanding of molecular pathways driving tolerance and immunity

κB-Ras Proteins Regulate Both NF-κB-Dependent Inflammation and Ral-Dependent Proliferation

The transformation of cells generally involves multiple genetic lesions that undermine control of both cell death and proliferation. We now report that κB-Ras proteins act as regulators of NF-κB and Ral pathways, which control inflammation/cell death and proliferation, respectively. Cells lacking κB-Ras therefore not only show increased NF-κB activity, which results in increased expression of inflammatory mediators, but also exhibit elevated Ral activity, which leads to enhanced anchorage-independent proliferation (AIP). κB-Ras deficiency consequently leads to significantly increased tumor growth that can be dampened by inhibiting either Ral or NF-κB pathways, revealing the unique tumor-suppressive potential of κB-Ras proteins. Remarkably, numerous human tumors show reduced levels of κB-Ras, and increasing the level of κB-Ras in these tumor cells impairs their ability to undergo AIP, thereby implicating κB-Ras proteins in human disease

Tumor necrosis factor receptor family costimulation increases regulatory T‐cell activation and function via NF‐κB

International audienceSeveral drugs targeting members of the TNF superfamily or TNF receptor superfamily (TNFRSF) are widely used in medicine or are currently being tested in therapeutic trials. However, their mechanism of action remains poorly understood. Here, we explored the effects of TNFRSF co-stimulation on murine Foxp3+ regulatory T cell (Treg) biology, as they are pivotal modulators of immune responses. We show that engagement of TNFR2, 4-1BB, GITR, and DR3, but not OX40, increases Treg proliferation and survival. Triggering these TNFRSF in Tregs induces similar changes in gene expression patterns, suggesting that they engage common signal transduction pathways. Among them, we identified a major role of canonical NF-κB. Importantly, TNFRSF co-stimulation improves the ability of Tregs to suppress colitis. Our data demonstrate that stimulation of discrete TNFRSF members enhances Treg activation and function through a shared mechanism. Consequently, therapeutic effects of drugs targeting TNFRSF or their ligands may be mediated by their effect on Tregs

Tumor necrosis factor receptor family costimulation increases regulatory T‐cell activation and function via NF‐κB

International audienceSeveral drugs targeting members of the TNF superfamily or TNF receptor superfamily (TNFRSF) are widely used in medicine or are currently being tested in therapeutic trials. However, their mechanism of action remains poorly understood. Here, we explored the effects of TNFRSF co-stimulation on murine Foxp3+ regulatory T cell (Treg) biology, as they are pivotal modulators of immune responses. We show that engagement of TNFR2, 4-1BB, GITR, and DR3, but not OX40, increases Treg proliferation and survival. Triggering these TNFRSF in Tregs induces similar changes in gene expression patterns, suggesting that they engage common signal transduction pathways. Among them, we identified a major role of canonical NF-κB. Importantly, TNFRSF co-stimulation improves the ability of Tregs to suppress colitis. Our data demonstrate that stimulation of discrete TNFRSF members enhances Treg activation and function through a shared mechanism. Consequently, therapeutic effects of drugs targeting TNFRSF or their ligands may be mediated by their effect on Tregs

PDK1 Is a Regulator of Epidermal Differentiation that Activates and Organizes Asymmetric Cell Division

Asymmetric cell division (ACD) in a perpendicular orientation promotes cell differentiation and organizes the stratified epithelium. However, the upstream cues regulating ACD have not been identified. Here, we report that phosphoinositide-dependent kinase 1 (PDK1) plays a critical role in establishing ACD in the epithelium. Production of phosphatidyl inositol triphosphate (PIP3) is localized to the apical side of basal cells. Asymmetric recruitment of atypical protein kinase C (aPKC) and partitioning defective (PAR) 3 is impaired in PDK1 conditional knockout (CKO) epidermis. PDK1CKO keratinocytes do not undergo calcium-induced activation of aPKC or IGF1-induced activation of AKT and fail to differentiate. PDK1CKO epidermis shows decreased expression of Notch, a downstream effector of ACD, and restoration of Notch rescues defective expression of differentiation-induced Notch targets in vitro. We therefore propose that PDK1 signaling regulates the basal-to-suprabasal switch in developing epidermis by acting as both an activator and organizer of ACD and the Notch-dependent differentiation program