Osteopontin Promotes Protective Antigenic Tolerance against Experimental Allergic Airway Disease

In the context of inflammation, osteopontin (Opn) is known to promote effector responses, facilitating a proinflammatory environment; however, its role during antigenic tolerance induction is unknown. Using a mouse model of asthma, we investigated the role of Opn during antigenic tolerance induction and its effects on associated regulatory cellular populations prior to disease initiation. Our experiments demonstrate that Opn drives protective antigenic tolerance by inducing accumulation of IFN-β–producing plasmacytoid dendritic cells, as well as regulatory T cells, in mediastinal lymph nodes. We also show that, in the absence of TLR triggers, recombinant Opn, and particularly its SLAYGLR motif, directly induces IFN-β expression in Ag-primed plasmacytoid dendritic cells, which renders them extra protective against induction of allergic airway disease upon transfer into recipient mice. Lastly, we show that blockade of type I IFNR prevents antigenic tolerance induction against experimental allergic asthma. Overall, we unveil a new role for Opn in setting up a tolerogenic milieu boosting antigenic tolerance induction, thus leading to prevention of allergic airway inflammation. Our results provide insight for the future design of immunotherapies against allergic asthma

Activin-A induces regulatory T cells that suppress T helper cell immune responses and protect from allergic airway disease

Activin-A is a pleiotropic cytokine that participates in developmental, inflammatory, and tissue repair processes. Still, its effects on T helper (Th) cell–mediated immunity, critical for allergic and autoimmune diseases, are elusive. We provide evidence that endogenously produced activin-A suppresses antigen-specific Th2 responses and protects against airway hyperresponsiveness and allergic airway disease in mice. Importantly, we reveal that activin-A exerts suppressive function through induction of antigen-specific regulatory T cells that suppress Th2 responses in vitro and upon transfer in vivo. In fact, activin-A also suppresses Th1-driven responses, pointing to a broader immunoregulatory function. Blockade of interleukin 10 and transforming growth factor β1 reverses activin-A–induced suppression. Remarkably, transfer of activin-A–induced antigen-specific regulatory T cells confers protection against allergic airway disease. This beneficial effect is associated with dramatically decreased maturation of draining lymph node dendritic cells. Therapeutic administration of recombinant activin-A during pulmonary allergen challenge suppresses Th2 responses and protects from allergic disease. Finally, we demonstrate that immune cells infiltrating the lungs from individuals with active allergic asthma, and thus nonregulated inflammatory response, exhibit significantly decreased expression of activin-A's responsive elements. Our results uncover activin-A as a novel suppressive factor for Th immunity and a critical controller of allergic airway disease

Elucidation of immuno-suppressive mechanisms during experimental autoimmune encephalomyelitis

Autoimmune responses against antigens of the central nervous system (CNS) are thought to cause diseases, such as multiple sclerosis (MS). MS is one of the most common autoimmune diseases of the CNS, initiated by excessive autoreactive immune responses in the CNS, where brain and spinal cord are affected, leading to destruction of the myelin that surrounds neurons. The exact triggers of the disease remain unknown. The existing knowledge concerning the mechanisms that govern disease pathogenesis comes from the studies in experimental autoimmune encephalomyelitis mouse model (EAE) in rodents and primates, as well as the in vitro studies with cells isolated from MS patients. The current therapies are not effective for all types of the disease, as it is very heterogeneous. The need for the development of therapeutic agents that could control excessive autoreactive immune responses in the CNS, concomitant with neuronal protection from apoptosis, is of great importance. Molecules that are expressed in the CNS microenvironment are possible mediators of the suppression of autoreactive CNS immune responses and neuronal protection. A molecule highly expressed in the CNS, with possible immunoregulatory actions is the neurosteroid dehydroepiandrosterone (DHEA). DHEA is synthesized by neurons and glia in the CNS, and many studies indicate its immunoregulatory effects, apart from its role in neuronal survival. In our studies, we investigated whether DHEA administration could suppress established EAE, as well as the mechanism of DHEA-mediated disease suppression. Our studies showed that DHEA, as well as a synthetic derivative of DHEA (BNN27) that does not metabolize to androgens and estrogens, treated established acute and relapsing-remitting EAE. Disease suppression was characterized by significantly decreased CNS inflammation and down-regulation of pathogenic TH1 and TH17 effector responses in both DLNs and CNS, concomitant with a significant expansion of CD4+ T regulatory cell subsets. This suppressive activity was dependent on IL-10. Treatment with DHEA and BNN27 rendered CD4+ T cells less pathogenic and suppressive in vitro and upon adoptive transfer in vivo. DHEA and BNN27 down-regulated CCR6 expression on DLN TH17 cells and suppressed TH17 cell differentiation and recall responses in vitro, while greatly induced IL-10 production. Furthermore, DHEA and BNN27 significantly suppressed TH17 differentiation of human naïve CD4+ T cells, as well as the TH1 and TH17 responses of MS patients ex vivo. These data indicate that derivatives of DHEA could be developed as therapeutic agents for autoimmune diseases, such as MS.Οι ανοσολογικές αποκρίσεις ενάντια σε αντιγόνα του κεντρικού νευρικού συστήματος (ΚΝΣ) θεωρείται ότι αποτελούν τη βάση της αιτίας νόσων, όπως η σκλήρυνση κατά πλάκας (ΣΚΠ). Η ΣΚΠ είναι μία από τις πιο συχνές αυτοάνοσες νόσους του ΚΝΣ, στην οποία προκαλείται καταστροφή της μυελίνης του εγκεφάλου και του νωτιαίου μυελού που περιβάλλει τα νευρικά κύτταρα. Τα ακριβή αίτια της νόσου παραμένουν άγνωστα. Η υπάρχουσα γνώση όσον αφορά τους μηχανισμούς που εμπλέκονται στην παθογένεια της νόσου προέρχεται από τις μελέτες που έχουν πραγματοποιηθεί στο μοντέλο της πειραματικής αυτοάνοσης εγκεφαλομυελίτιδας (ΠΑΕ) σε τρωκτικά και πρωτεύοντα, καθώς και από in vitro μελέτες σε απομονωμένα κύτταρα ασθενών με ΣΚΠ. Οι υπάρχουσες θεραπείες δεν είναι αποτελεσματικές για όλες τις μορφές της νόσου, καθώς παρουσιάζει μεγάλη ετερογένεια. Η ανάγκη για την ανάπτυξη θεραπευτικών παραγόντων που να μπορούν να περιορίσουν τις ανεξέλεγκτες αυτοδραστικές αποκρίσεις στο ΚΝΣ, αλλά ταυτόχρονα να προστατέψουν τους νευρώνες από την απομυελίνωση, είναι μεγάλης σημασίας. Μόρια που εκφράζονται στο μικροπεριβάλλον του ΚΝΣ είναι πιθανοί διαμεσολαβητές της καταστολής της αυτοάνοσης ανοσολογικής απόκρισης του ΚΝΣ και της προστασίας των νευρώνων. Ένα μόριο που εκφράζεται στο ΚΝΣ με πιθανές ρυθμιστικές δράσεις κατά της αυτοάνοσης ανοσολογικής απόκρισης του ΚΝΣ είναι το νευροστεροειδές δεϋδροεπιανδροστερόνη (DHEA). Η DHEA συντίθεται από τους νευρώνες και τη γλοία στο ΚΝΣ και σε πολλές μελέτες υποδεικνύουν ότι, εκτός από την προστατευτική της δράση στους νευρώνες, έχει πιθανές ανοσορυθμιστικές δράσεις επίσης. Στις μελέτες μας, εξετάσαμε εάν η χορήγηση της DHEA μπορεί να καταστείλει τα συμπτώματα της ΠΑΕ, όταν έχουν ήδη εκδηλωθεί, καθώς και το μηχανισμό της διαμεσολαβούμενης προστασίας από τη νόσο.Είδαμε ότι η θεραπευτική χορήγηση της DHEA και ενός συνθετικού παραγώγου αυτής, το οποίο δεν μεταβολίζεται σε ανδρογόνα και οιστρογόνα (ΒΝΝ27), σε ποντίκια με συμπτώματα ΠΑΕ, είχε ως αποτέλεσμα τη σχεδόν πλήρη καταστολή της οξείας ΠΑΕ, καθώς επίσης και της ΠΑΕ με εναλλασσόμενες εξάρσεις και υφέσεις. Η καταστολή της νόσου χαρακτηρίστηκε από σημαντικά μειωμένη φλεγμονή στο ΚΝΣ και δραματικά μειωμένη απόκριση των αυτό-δραστικών TH1 και TH17 κυττάρων στους συνοδούς λεμφαδένες και το ΚΝΣ, ταυτόχρονα με εξαιρετικά σημαντικό πολλαπλασιασμό υποομάδων των CD4+ T ρυθμιστικών κυττάρων.Η θεραπεία με την DHEA και το συνθετικό ΒΝΝ27 είχε ως αποτέλεσμα την επαγωγή CD4+ T κυττάρων με σημαντικά μειωμένη παθογονικότητα, αλλά και εξαιρετικά κατασταλτικές δράσεις in vivo και in vitro. Μάλιστα, η διαμεσολαβούμενη από την DHEA και το ΒΝΝ27 μειωμένη παθογονικότητα των CD4+ T κυττάρων βρέθηκε να οφείλεται εν μέρη στη σημαντική μείωση της έκφρασης του υποδοχέα χημειοκινών CCR6 στην επιφάνεια των TH17 κυττάρων στους συνοδούς λεμφαδένες. Η κατασταλτική δράση της DHEA και του συνθετικού ΒΝΝ27 στην ΠΑΕ ήταν εξαρτώμενη από την επαγωγή της ανοσοκατασταλτικής κυτταροκίνης ιντερλευκίνη-10 (IL-10). Επιπλέον, σε in vitro μελέτες, η DHEA και το ΒΝΝ27 κατέστειλαν τη διαφοροποίηση ανθρώπινων και μυϊκών TH17 κυττάρων, καθώς και τις δευτερογενείς TH17 ανοσολογικές αποκρίσεις, μέσω αύξησης της IL-10. Παράλληλα, η DHEA και το ΒΝΝ27 κατέστειλαν σημαντικά τις ex vivo αποκρίσεις των TH1 και TH17 κυττάρων ασθενών με ΣΚΠ. Όλα τα παραπάνω αποτελέσματα υποδεικνύουν ότι συνθετικά παράγωγα της DHEA, όπως είναι το ΒΝΝ27, θα μπορούσαν να αποτελέσουν πιθανούς θεραπευτικούς παράγοντες για αυτοάνοσες νόσους, όπως η ΣΚΠ

TIGIT Enhances Antigen-Specific Th2 Recall Responses and Allergic Disease

T cell Ig and ITIM domain receptor (TIGIT), expressed on T, NK, and regulatory T cells, is known as an inhibitory molecule that limits autoimmunity, antiviral and antitumor immunity. In this report, we demonstrate that TIGIT enhances Th2 immunity. TIGIT expression was upregulated in activated Th2 cells from mice with experimental allergic disease and in Th2 polarization cultures. In addition, its high-affinity ligand CD155 was upregulated in mediastinal lymph node dendritic cells from allergic mice. In an in vitro setting, we observed that Tigit expression in Th2 cells and its interaction with CD155 expressed in dendritic cells were important during the development of Th2 responses. In addition, blockade of TIGIT inhibited Th2, but had no effect on either Th1 or Th17 polarization. In vivo blockade of TIGIT suppressed hallmarks of allergic airway disease, such as lung eosinophilia, goblet cell hyperplasia, Ag-specific Th2 responses, and IgE production, and reduced numbers of T follicular helper and effector Th2 cells. Thus, TIGIT is critical for Th2 immunity and can be used as a therapeutic target, especially in light of recent findings showing TIGIT locus hypomethylation in T cells from pediatric patients with allergic asthma

Osteopontin expression by CD103−dendritic cells drives intestinal inflammation

Intestinal CD103− dendritic cells (DCs) are pathogenic for colitis. Unveiling molecular mechanisms that render these cells proinflammatory is important for the design of specific immunotherapies. In this report, we demonstrated that mesenteric lymph node CD103− DCs express, among other proinflammatory cytokines, high levels of osteopontin (Opn) during experimental colitis. Opn expression by CD103− DCs was crucial for their immune profile and pathogenicity, including induction of T helper (Th) 1 and Th17 cell responses. Adoptive transfer of Opn-deficient CD103− DCs resulted in attenuated colitis in comparison to transfer of WT CD103− DCs, whereas transgenic CD103− DCs that overexpress Opn were highly pathogenic in vivo. Neutralization of secreted Opn expressed exclusively by CD103− DCs restrained disease severity. Also, Opn deficiency resulted in milder disease, whereas systemic neutralization of secreted Opn was therapeutic. We determined a specific domain of the Opn protein responsible for its CD103− DC-mediated proinflammatory effect. We demonstrated that disrupting the interaction of this Opn domain with integrin α9, overexpressed on colitic CD103− DCs, suppressed the inflammatory potential of these cells in vitro and in vivo. These results add unique insight into the biology of CD103− DCs and their function during inflammatory bowel disease

ERb-Dependent Direct Suppression of Human and Murine Th17 Cells and Treatment of Established Central Nervous System Autoimmunity by a Neurosteroid

Multiple sclerosis (MS), an autoimmune disease of the CNS, is mediated by autoreactive Th cells. A previous study showed that the neurosteroid dehydroepiandrosterone (DHEA), when administered preclinically, could suppress progression of relapsing-remitting experimental autoimmune encephalomyelitis (EAE). However, the effects of DHEA on human or murine pathogenic immune cells, such as Th17, were unknown. In addition, effects of this neurosteroid on symptomatic disease, as well as the receptors involved, had not been investigated. In this study, we show that DHEA suppressed peripheral responses from patients with MS and reversed established paralysis and CNS inflammation in four different EAE models, including the 2D2 TCR-transgenic mouse model. DHEA directly inhibited human and murine Th17 cells, inducing IL-10–producing regulatory T cells. Administration of DHEA in symptomatic mice induced regulatory CD4+ T cells that were suppressive in an IL-10–dependent manner. Expression of the estrogen receptor b by CD4+ T cells was necessary for DHEA-mediated EAE amelioration, as well as for direct downregulation of Th17 responses. TGF-b1 as well as aryl hydrocarbon receptor activation was necessary for the expansion of IL-10–producing T cells by DHEA. Thus, our studies demonstrate that compounds that inhibit pathogenic Th17 responses and expand functional regulatory cells could serve as therapeutic agents for autoimmune diseases, such as MS