The aim for this thesis was to identify prognostic factors for chronic diabetes complications that exist at the time of diabetes diagnosis. Low level of education (<12 years) and low income (<60% of median) was found to increase the risk to have high (>70 mmol/mol) HbA1c at the time of diagnosis with 34 % and 35 %, respectively. Prevalence of diabetic retinopathy (DR) was 12% in a cohort of patients newly diagnosed with diabetes. Diabetic macular edema was present in 11% of patients with type 2 diabetes (T2D) and 13% of those with Latent Autoimmune Diabetes in Adults (LADA). Low beta cell function and low level of education increased the risk for DR with 110% and 43%, respectively. For every unit of increase in body mass index, the risk for DR was reduced by 3%. The cellular immunology of LADA patients was a mixture of that observed in both type 1 (T1D) and T2D patients. Compared to patients with T1D, LADA patients had more B-regulatory lymphocytes and antigen presenting cells capable of producing interleukine-35. This indicates a higher anti-inflammatory capacity in LADA patients compared to type T1D patients. By imputing age, body mass index, HbA1c at diagnosis, beta cell function and insulin resistance in a cluster analysis, five distinct diabetes clusters were identified. The four clusters representing T2D patients differed in incidence of DR, nephropathy and non-alcoholic fatty liver disease. This was replicated with similar results in three geographically separate populations. By studying socioeconomic background and factors present at the time of diagnosis we can better predict prognosis for chronic diabetes complications. These findings may facilitate better-targeted diabetes screening programs and more individually tailored treatment regimes.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by the immune-mediated destruction of insulin-producing beta-cells of pancreatic islets, culminating in critical insulin deficiency. Both genetic and environmental factors likely orchestrate an immune-mediated functional loss of beta cell mass, leading to the clinical manifestation of disease and lifelong dependence on insulin therapy. Additional evidence suggests the role of innate and adaptive immune mechanisms leading to inflammation in beta cells mediated by proinflammatory cytokines and chemokines, activation of beta-cell-reactive T cells,and failure of immune tolerance. Viral infections have been proposed as causal determinants or initiating triggers for T1D but remain unproven. Understanding the relationship between viral infections and the development of T1D is essential for T1D prevention. Importantly, virus-induced innate immune responses, particularly type I interferon (IFN-I, IFN-a/b), have been implicated in the initiation of islet autoimmunity and development of T1D. The goal of my thesis project is to investigate how the IFN-I signaling pathway affects the development of T1D using the LEW.1WR1 rat model of autoimmune diabetes. My hypothesis is that disrupting IFN-Isignaling via functional deficiency of the IFN-I interferon receptor (IFNAR) prevents or delays the development of virus-induced diabetes.For this purpose, I generated IFNAR subunit 1(IFNAR1)-deficient LEW.1WR1 rats using CRISPR-Cas9 genome editing and confirmed the functional disruption of IFNAR1. The absence of IFNAR1 results in a significant delay in onset and frequency of diabetes following poly I:C challenge and reduces the incidence of insulitis after poly I:C treatment. The frequency of diabetes induced by Kilham rat virus (KRV) is also reduced in IFNAR1-deficient LEW.1WR1 rats. Furthermore, I observe a decrease in CD8+T cells in spleens from KRV-infected IFNAR1-deficient rats relative to that in KRV-infected wild-type rats. While splenic regulatory T cells are depleted in WT rats during KRV-infection, no such decrease is observed in KRV-infected IFNAR1-deficient rats. A comprehensive bulk RNA-seq analysis reveals a decrease of interferon-stimulated genes and inflammatory gene expression in IFNAR1-deficient rats relative to wild-type rats following KRV challenge. Collectively, the results from these studies provided mechanistic insights into the essential role of virus-induced, IFN-I-initiated innate immune responses in the early phase of autoimmune diabetes pathogenesis.

Le diabète de type 1 (DT1) est une maladie auto-immune caractérisée par la destruction des cellules β pancréatiques par les cellules immunitaires, ce qui entraîne une insuffisance en insuline. L’étude des souris Non-Obese Diabetic (NOD), qui développent spontanément le diabète auto-immun, a permis l'identification de plusieurs loci de susceptibilité associés au diabète, appelés Idds. D’ailleurs, Idd1 est lié au locus du CMH. L’utilisation de souris congéniques NOD.B6-Idd1 et B6.NOD-Idd1 a démontré qu’Idd1 est nécessaire mais insuffisant pour la progression du diabète auto-immun. Précédemment, nous avons démontré que les allèles de résistance au locus Idd2 offrent une protection significative contre l’apparition du diabète auto-immun, semblable à Idd1. Pour identifier les facteurs génétiques minimaux requis pour l'apparition du DT1, nous avons introduit les loci NOD Idd1 et Idd2 chez des souris B6, générant des souris doubles congéniques B6.Idd1.Idd2. Bien que la combinaison de Idd1 et Idd2 n’est pas suffisante pour induire l’apparition du diabète, nous avons observé une infiltration immunitaire dans le pancréas exocrine des souches congéniques B6 Idd2. De plus, nous avons observé d'importantes différences phénotypiques dans les sous-populations de lymphocytes T chez les souris B6.Idd1.Idd2 par rapport aux souris simple congéniques, suggérant une interaction épistatique entre Idd1 et Idd2 dans la modulation des fonctions des lymphocytes T. De plus, des augmentations de neutrophiles et de la fibrose spécifiques à Idd2 ont été découvertes, suggérant qu’Idd2 est impliqué dans le processus cellulaire inflammatoire du diabète auto-immun. Dans l’ensemble, ces données montrent que la combinaison des allèles de susceptibilité Idd1 et Idd2 ne mène pas à la progression du diabète auto-immun. Des facteurs génétiques ou environnementaux supplémentaires sont donc nécessaires pour provoquer le diabète auto-immun chez la souris. Néanmoins, nous constatons que les allèles NOD au niveau des locus Idd2 coopèrent pour induire une inflammation et une infiltration immunitaire dans le pancréas. / Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of pancreatic β cells by immune cells, leading to an insulin deficiency. Non-Obese Diabetic (NOD) mice, which spontaneously develop autoimmune diabetes, have enabled the identification of several loci associated with diabetes susceptibility, termed Idds. Notably, Idd1 is linked to the MHC locus and resistance alleles at this locus provide full protection from diabetes onset. Conversely, C57BL/6 (B6) mice bearing NOD Idd1 alleles exhibit immune infiltration in the pancreas without causing overt diabetes. These results show that NOD Idd1 alleles are necessary but not sufficient for autoimmune diabetes progression. In a previous study, we demonstrated that diabetes resistance alleles at the Idd2 locus provide significant protection from autoimmune diabetes onset, second to Idd1. To identify the minimal genetic factors required for T1D onset, we introduced the NOD Idd1 and Idd2 loci in B6 mice, generating B6.Idd1.Idd2 double congenic mice. Although the introduction of susceptibility alleles at both Idd1 and Idd2 was not sufficient to induce diabetes onset, we observed immune infiltration in the exocrine pancreas of B6 Idd2 congenic strains. In addition, we observed important phenotypic differences in T cell subsets in B6.Idd1.Idd2 mice relative to single congenic mice, suggesting epistatic interaction between Idd1 and Idd2 in modulating T cell functions. Moreover, Idd2-specific increases in neutrophils and fibrosis were discovered, suggesting that Idd2 is involved in the inflammatory cellular process of autoimmune diabetes. Altogether, these data show that susceptibility alleles at Idd1 and Idd2 together are not sufficient to autoimmune diabetes progression. Additional genetic factors or environmental triggers are therefore required to cause autoimmune diabetes in mice. Still, we find that NOD alleles at the Idd2 loci cooperate to induce inflammation and immune infiltration in the pancreas.

Plasmacytoid dendritic cells (pDCs) regulate innate and adaptive immunity. Neurotrophins and their receptors control the function of neuronal tissue. In addition, they have been demonstrated to be part of the immune response but little is known about the effector immune cells involved. We report, for the first time, the expression and immune-regulatory function of the low affinity neurotrophin receptor p75 neurotrophin receptor (p75NTR) by the antigen-presenting pDCs, mediated by toll-like receptor (TLR) 9 activation and differential phosphorylation of interferon regulatory factor 3 and 7. The modulation of p75NTR on pDCs significantly influences disease progression of asthma in an ovalbumin-induced mouse model mediated by the TLR9 signaling pathway. p75NTR activation of pDCs from patients with asthma increased allergen-specific T cell proliferation and cytokine secretion in nerve growth factor concentration-dependent manner. Further, p75NTR activation of pDCs delayed the onset of autoimmune diabetes in RIP-CD80GP mice and aggravated graft-versus-host disease in a xenotransplantation model. Thus, p75NTR signaling on pDCs constitutes a new and critical mechanism connecting neurotrophin signaling and immune response regulation with great therapeutic potential for a variety of immune disorders.

Plasmacytoid dendritic cells (pDCs) regulate innate and adaptive immunity. Neurotrophins and their receptors control the function of neuronal tissue. In addition, they have been demonstrated to be part of the immune response but little is known about the effector immune cells involved. We report, for the first time, the expression and immune-regulatory function of the low affinity neurotrophin receptor p75 neurotrophin receptor (p75NTR) by the antigen-presenting pDCs, mediated by toll-like receptor (TLR) 9 activation and differential phosphorylation of interferon regulatory factor 3 and 7. The modulation of p75NTR on pDCs significantly influences disease progression of asthma in an ovalbumin-induced mouse model mediated by the TLR9 signaling pathway. p75NTR activation of pDCs from patients with asthma increased allergen-specific T cell proliferation and cytokine secretion in nerve growth factor concentration-dependent manner. Further, p75NTR activation of pDCs delayed the onset of autoimmune diabetes in RIP-CD80GP mice and aggravated graft-versus-host disease in a xenotransplantation model. Thus, p75NTR signaling on pDCs constitutes a new and critical mechanism connecting neurotrophin signaling and immune response regulation with great therapeutic potential for a variety of immune disorders.