<p>Within the field of immunology, the existence of autoimmune diseases presents a unique set of challenges. The immune system typically protects the host by identifying foreign pathogens and mounting an appropriate response to eliminate them. Great strides have been made in understanding how foreign pathogens are identified and responded to, leading to the development of powerful immunological tools, such as vaccines and a myriad of models used to study infectious diseases and processes. However, it is occasionally possible for host tissues themselves to be inappropriately identified as foreign, prompting an immune response that attempts to eliminate the host tissue. The immune system has processes in place, referred to as selection, designed to prevent the development of cells capable of recognizing the self as foreign. While a great deal of work has been invested in understanding these processes, many concrete answers remain elusive. </p><p>Our laboratory, which focuses on understanding the roles of E and Id proteins in lymphocyte development, has established the Id3 knockout mouse as a model of autoimmune disease. Id3 knockout mice develop a disease reminiscent of human Sj&#1255;gren's Syndrome, an autoimmune disease that progressively damages the salivary and lachrymal glands. Continued study of this model has yielded interesting results. These include the identification of CD4+ T cells as initiators of disease as well as the identification of the cytokine Interleukin 13 (IL-13) as a potential causative agent. However, the source of IL-13, its true role as a causative agent of disease, as well as the developmental basis for its elevated expression remained elusive. </p><p>To this end, I utilized a reporter gene that enabled me to detect cells producing IL-13 as well as test the effects of IL-13 deletion on disease progression. Using this system, I was able to identify both CD4+ T cells and &#947;&#948; T cells as major sources of IL-13. I was also able to determine that elimination of IL-13 in Id3 knockout mice was sufficient to block the development of disease symptoms, reinforcing the hypothesis that IL-13 is a causative agent in disease initiation. Finally, I attempted to better characterize the phenotype of cells producing IL-13. These experiments indicated that the T cell receptor (TCR) repertoire of Id3 knockout mice is markedly different than that of wild-type (WT) mice. Furthermore, cells bearing certain TCRs appeared to express IL-13 at dramatically different rates, indicating that certain TCRs may be predisposed to IL-13 particular effector fates.</p> / Dissertation

The tyrosine kinase 2 (TYK2) gene was first implicated in autoimmune disease in 2009 when a nonsynonymous single nucleotide polymorphism (nsSNP) in TYK2 was reported to be associated with multiple sclerosis (MS). The immunological function of TYK2, as a kinase involved in signal transduction downstream of numerous different cytokine receptors, further strengthened the candidacy of the gene as an MS-relevant risk factor. More recently, this nsSNP has been associated with several other autoimmune conditions. In addition, another three different SNPs in the region have been found to be associated with a number of autoimmune diseases, sometimes in opposing directions. Considering the complex genetic association pattern that is emerging for the TYK2 region across autoimmune conditions, it was hypothesised that this complexity reflects shared but also distinct pathogenic mechanisms, with the consequences of disease-associated SNPs being unlikely to all be restricted to genotype-dependent effects influencing TYK2. Therefore, the main aim of the work presented in this thesis has been to address this hypothesis by investigating the functional consequences of the disease-associated SNPs in the TYK2 gene region. Using an in vitro cell line system and primary human immune cells, obtained from a genotype-selectable donor cohort, protection at the MS-associated nsSNP was found to correlate with reduced TYK2-mediated signalling downstream of the type I interferon receptor. However, other cytokine signalling pathways were not affected, indicating a greater specificity to the function of TYK2 than has previously been appreciated. For the other SNPs in the region, substantial effects on TYK2 were not observed but immune cell subset-specific correlations with RNA-level expression of other genes in the region were identified. Thus, this is the first study to support the concept that a careful cross-comparative analysis of SNP association patterns in a single genomic region across multiple autoimmune diseases can have significant implications for enabling the delineation of pathways common or specific to different conditions, and this is of particular importance for drug repositioning strategies.

La myasthénie (Myasthenia Gravis) est une maladie neuromusculaire impliquant des auto-anticorps dirigés majoritairement contre le récepteur à l’acétylcholine (RACh) et entrainant une fatigabilité musculaire. Ces auto-anticorps pathogènes sont produits principalement par le thymus qui présente une hyperplasie caractérisée par le développement de centres germinatifs ectopiques. De récentes études ont démontré la surexpression de chimiokines dans le thymus des patients et la présence anormale de vaisseaux sanguins de type HEV (cellules endothéliales à paroi haute). L’objectif de ma thèse a été de mieux comprendre les mécanismes physio-pathologiques conduisant à l’hyperplasie thymique en étudiant le rôle des chimiokines dans la myasthénie.Nous avons tout d’abord démontré que le nombre de HEV thymiques est proportionnel au degré d’hyperplasie suggérant leur implication directe dans le recrutement des cellules périphériques. En analysant les chimiokines exprimées sur ces HEV, nous observons l’expression sélective de SDF-1/CXCL12. En parallèle, la présence de lymphocytes B, de cellules dendritiques myéloïdes ou plasmacytoïdes et de monocytes/macrophages exprimant le récepteur au SDF-1, CXCR4, a été observée au niveau des HEV. En périphérie, nous montrons une diminution de l’expression de CXCR4 ainsi que du nombre de mDC et de monocytes dans le sang des patients suggérant le recrutement de ces cellules dans le thymus.Le thymus des patients myasthéniques est aussi caractérisé par une surexpression de la chimiokine CXCL13 par les cellules épithéliales thymiques. Pour mieux comprendre les mécanismes conduisant à l’hyperplasie thymique, nous avons développé un modèle de souris transgéniques avec surexpression thymique de CXCL13. Dans le thymus de ces souris, nous observons une surexpression de CXCL13 et une augmentation de nombre de lymphocytes B, notamment pour les souris jeunes. Nous étudions maintenant si l’immunisation de ces souris avec du RACh purifié induit une myasthénie expérimentale associée à une hyperplasie thymique ; un nouveau modèle animal de la maladie qui se rapprocherait mieux de la pathologie humaine.Dans la myasthénie, le thymus est aussi caractérisé par une signature inflammatoire, avec notamment une surexpression d’interféron de type I (IFN-I). Nous démontrons que le Poly(I:C), une molécule mimant les effets des ARN double-brin, induit spécifiquement la surexpression du RACh-α par les cellules épithéliales thymiques humaines via la libération d’IFN-I. L’IFN-I entraine aussi la surexpression des chimiokines CXCL13 et CCL21 comme dans le thymus des patients myasthéniques. Chez des souris C57Bl6, mais pas chez des souris KO pour le récepteur à l’IFN-I, des injections de Poly(I:C) entrainent des modifications thymiques avec une surexpression spécifique de RACh-α, d’IFN-I et de chimiokines. En périphérie, ces injections entrainent l’apparition dans le sérum d’anticorps contre le RACh-α spécifiques de la myasthénie.L’ensemble de ces résultats suggère que dans le thymus des patients myasthéniques, le développement anormal de HEV exprimant du SDF-1 et la surexpression de CXCL13 joueraient un rôle central dans le recrutement de cellules périphériques. Ces cellules, une fois dans l’environnement inflammatoire caractéristique du thymus myasthénique, pourraient alors développer une réaction auto-immune contre le RACh. De nouvelles molécules thérapeutiques contrôlant l’expression de ces chimiokines ou l’angiogenèse pourraient diminuer le développement de l’hyperplasie thymique et éviteraient la thymectomie ou l’utilisation des glucocorticoïdes par les patients atteints de myasthénie. / Autoimmune myasthenia gravis (MG) is a muscular disease mediated by autoantibodies, mainly directed against the acetylcholine receptor (AChR). The pathogenic antibodies are especially produced in the thymus, which is often characterized by a hyperplasia with germinal centers. Recent studies demonstrated the overexpression of chemokines and the abnormal development of high endothelial venules (HEV) in the MG thymus. The aim of my thesis was to better understand the mechanisms that lead to thymic hyperplasia in MG by analyzing the role of chemokines in peripheral cell recruitment. We demonstrated that the number of HEVs correlated with the degree of hyperplasia suggesting a direct link between HEVs and peripheral cell recruitment. To define its mechanism of action, we examined which chemokines were expressed on thymic HEVs. We uniquely detected SDF-1 and observed that B cells, myeloid dendritic cells (mDCs), plasmacytoid DCs and monocytes/macrophages that expressed the SDF-1 receptor CXCR4 localized inside and around thymic HEV. In parallel we observed a decreased CXCR4 expression and a decreased number of mDCs and also monocytes in the periphery suggesting their recruitment to the MG thymus. As the MG thymus was recently characterized by the overexpression of CXCL13 in thymic epithelial cells (TECs), we investigated its contribution to thymic hyperplasia. We therefore generated a transgenic mouse model overexpressing in medullary TECs CXCL13 under the control of keratin 5. We demonstrated that transgenic K5-CXCL13 mice specifically overexpressed CXCL13 in the thymus, while no other tested chemokines were upregulated. Preliminary results showed that elevated levels of CXCL13 resulted in an increased number of B cells in the thymus of transgenic mice, which localized preferentially in loose aggregates in medullary areas. We are presently investigating if immunization with purified AChR induces experimental MG with thymic hyperplasia in these mice. Myasthenic mice with a hyperplastic thymus could present a new animal model for MG with a phenotype that is closer to the human disease than the current MG model. As the hyperplastic MG thymus displays the hallmarks of a viral signature, we investigated the effect of pathogen-associated molecules on thymic changes associated with MG. We demonstrated that dsRNA signaling induced by Poly(I:C) specifically triggers the overexpression of α-AChR in human TECs through the release of IFN-I. We also observed that IFN-I was able to upregulate CXCL13 and CCL21, similarly to what is observed in the MG thymus. In addition, Poly(I:C) injections in wildtype mice, but not in IFN-I receptor KO mice, specifically increase thymic expression of α-AChR and, in parallel, CXCL13 and CCL21 expression. In periphery, Poly(I:C) even induced an anti-AChR autoimmune response characterized by a significant production of serum anti-AChR antibodies and a specific proliferation of B cells. Overall the results obtained in the course of my PhD showed that the abnormal development of SDF-1-expressing HEVs and the CXCL13 overexpression play a central role in the recruitment of peripheral cells to the MG thymus. Once these cells have arrived in the inflammatory environment, which is characteristic for MG, they could develop an autoimmune reaction against AChR. New therapeutic molecules that control chemokine expression and angiogenic processes could diminish the development of thymic hyperplasia and avoid thymectomy or the use of corticoids.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.) in Biochemistry and Molecular Biology--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 113-165).

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Interactions between the immune system and the nervous system are currently underappreciated, assumed to play minor mechanistic roles in disease pathogenesis. In contrast, our laboratory has demonstrated the importance of this relationship with significant impact, initially in Type 1 Diabetes (T1D). The experiments presented here build on our previous work to provide insights into the etiology of Multiple Sclerosis (MS) and Type 2 Diabetes (T2D). Transient Receptor Potential Vanilloid-1 (TRPV1) is an ion channel expressed on peripheral sensory afferent neurons that fundamentally control T1D pathogenesis. Here we show that mice with genetic ablation of TRPV1 are protected from EAE progression, attributable to reduced central nervous system (CNS) leukocyte passage. The pathogenic role of TRPV1 in permeabilizing the blood-CNS barriers may also translate to MS, as patients with progressive disease show a significant mutation bias within the TRPV1 gene. We were simultaneously intrigued by the growing worldwide obesity epidemic, and we observed that obese mice develop more severe EAE compared to lean mice. This was mechanistically linked to an expansion of TH17 cells, driven by sustained rises of IL-6 in obese mice. This research implies new therapeutic opportunities for the many obese patients with diverse autoimmune diseases. Finally, the immune system, obesity, and T2D are functionally linked, and we contributed to research that uncovered a large presence of immune cells in adipose tissue that drive insulin resistance. Manipulation of T cells and B cells affects local inflammation as well as whole-body insulin resistance and glucose homeostasis. Intriguingly, auto-antibodies in insulin resistant individuals are specific for a number of unique proteins, including glial fibrillary acidic protein (GFAP), initially shown by our laboratory to play a key role in T1D progression. We further characterized the autoimmune and neuronal progression elements that steer disease pathogenesis, and observed that administration of a vaccine containing GFAP is able to dramatically reduce weight gain and insulin resistance in mice. The data presented in this thesis provide a number of novel, mechanistic observations linking the immune and nervous systems in disease, and implies several potential avenues for treatment.

Interactions between the immune system and the nervous system are currently underappreciated, assumed to play minor mechanistic roles in disease pathogenesis. In contrast, our laboratory has demonstrated the importance of this relationship with significant impact, initially in Type 1 Diabetes (T1D). The experiments presented here build on our previous work to provide insights into the etiology of Multiple Sclerosis (MS) and Type 2 Diabetes (T2D). Transient Receptor Potential Vanilloid-1 (TRPV1) is an ion channel expressed on peripheral sensory afferent neurons that fundamentally control T1D pathogenesis. Here we show that mice with genetic ablation of TRPV1 are protected from EAE progression, attributable to reduced central nervous system (CNS) leukocyte passage. The pathogenic role of TRPV1 in permeabilizing the blood-CNS barriers may also translate to MS, as patients with progressive disease show a significant mutation bias within the TRPV1 gene. We were simultaneously intrigued by the growing worldwide obesity epidemic, and we observed that obese mice develop more severe EAE compared to lean mice. This was mechanistically linked to an expansion of TH17 cells, driven by sustained rises of IL-6 in obese mice. This research implies new therapeutic opportunities for the many obese patients with diverse autoimmune diseases. Finally, the immune system, obesity, and T2D are functionally linked, and we contributed to research that uncovered a large presence of immune cells in adipose tissue that drive insulin resistance. Manipulation of T cells and B cells affects local inflammation as well as whole-body insulin resistance and glucose homeostasis. Intriguingly, auto-antibodies in insulin resistant individuals are specific for a number of unique proteins, including glial fibrillary acidic protein (GFAP), initially shown by our laboratory to play a key role in T1D progression. We further characterized the autoimmune and neuronal progression elements that steer disease pathogenesis, and observed that administration of a vaccine containing GFAP is able to dramatically reduce weight gain and insulin resistance in mice. The data presented in this thesis provide a number of novel, mechanistic observations linking the immune and nervous systems in disease, and implies several potential avenues for treatment.

No description available.

The BRB consists of both capillary endothelial cells (REC) and retinal pigment epithelial cells (RPE). Both cell types have been suggested as potential activators of circulating T cells. In this study, an <I>in vitro</I> model using cultured rat REC and syngeneic T cells was developed. Furthermore RPE and for the purpose of comparative studies, AEC were also successfully cultured. It was demonstrated that activation of T lymphocyte LFA-1 is a critical event governing the adhesion of T cells to RPE and REC as IFN-γ induced up-regulation of RPE and REC ICAM-1 expression did not increase binding of resting T lymphocytes. The enhanced adhesion of activated lymphocytes (but not resting lymphocytes) to normal and IFN-γ treated RPE and REC was inhibited by LFA-1 mAb and to a lesser extent by ICAM-1 mAb but not OX34 (CD2). Treatment of lymphocytes with the anti-VLA-4 mAb resulted in differential effects on binding to AEC and REC. MAb to VLA-4 significantly blocked enhanced adhesion of activated T cells to AEC but not to REC. The results also demonstrated that VLA-4 mAb significantly inhibited unactivated T cell binding to IFNγ+TNFα+LPS stimulated AEC but not REC, suggesting that VLA-4 may also function in an activation-independent manner. It was shown that activation of T cells can enhance their migratory activity across cultured REC monolayers. Migration was decreased by both adhesion receptor-dependent mechanisms i.e., mAb to LFA-1 (but not ICAM-1) and adhesion receptor-independent mechanisms by means of PGE<SUB>2</SUB>. The results of this thesis have shown that activation of LFA-1 is required for functioning of the LFA-1/ICAM-1-mediated lymphocyte adhesion and migration. In addition to the role of adhesion molecules, inflammatory mediator PGE<SUB>2</SUB>, but not NO<SUP>o</SUP>, was found to be important in regulation of T cell adhesion and migration across REC.