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Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by loss of immune tolerance and the production of auto-antibodies which target various nuclear components. There is a 9:1 women to men ratio among lupus patients, indicating differing mechanisms of lupus pathogenesis between the sexes. Although lupus patients may develop many different manifestations, lupus nephritis (LN) remains to be one of the most devastating manifestations and an indicator of poor prognosis. Although both sexes develop LN, the nephritis in males often develops more rapidly and is more severe. Necrotic cell death is a characteristic of lupus nephritis and contributes to the exacerbation of the inflammatory immune response within the glomeruli. Previously our laboratory found that absence or pharmacological inhibition of Poly [ADP-ribose] polymerase 1 (PARP-1), an enzyme involved in necrotic cell death, results in milder nephritis, reduced necrotic lesions, and higher survival rates only among males. Although RIPK3-mediated necrosis was a likely candidate for inducing necrosis during female LN, murine models of glomerulonephritis revealed that the development of LN occurs independently of RIPK3. In addition, during LN, there is no crosstalk between the RIPK3- and PARP-1 mediated pathways to induce necrotic cell death. The sex bias in SLE indicates sex hormones may play a role in pathogenesis. Interestingly, estrogen receptor alpha (ERα) in the renal tissue is highly expressed and the renal specific estrogen-induced gene activation is second only to that of reproductive organs. The absence of estrogen receptor alpha protects female mice from developing nephritis, despite the presence of immune complexes in the kidneys and production of pro-inflammatory cytokines. Analysis of gene expression changes during LN progression indicate the protection seen in ERKO females may be due to alterations in metabolic pathways, including PPAR and retinol metabolism. These results demonstrate the complexity of lupus nephritis. Despite the presence of necrosis in LN, this manifestation occurs in a RIPK3-independent manner, which leaves the pathway responsible for necrosis in female kidneys to still be investigated. In addition, lupus nephritis occurs in an ER-dependent manner in females, demonstrating the significant impacts sex-hormone environments play in the pathogenesis of immune-mediated nephropathies. / Biomedical Sciences

Systemic lupus erythematosus (SLE) is complex autoimmune disease in which autoantibodies form against double stranded DNA (dsDNA) and nuclear antigens. Autoantigen immune complexes form, deposit in the vasculature, and cause multisystem organ damage. Both genetic and environmental factors contribute to the development of SLE. This thesis will explore three major themes found in the study of SLE: 1) Bacterial infection as an environmental trigger, 2) cytokine dysregulation in immune cells, and 3) the treatment of end organ damage in the form of lupus nephritis. Viral infections have long been associated with the development of systemic autoimmune disease, but the mechanisms by which chronic bacterial infections may promote autoimmunity remain unclear. In chapter three we show that a component of bacterial biofilms, the amyloid-like protein “curli”, irreversibly forms fibers with bacterial or eukaryotic DNA during biofilm formation. This interaction accelerates amyloid polymerization and creates potent immunogenic complexes that activate immune cells, including dendritic cells, to produce cytokines such as type I interferons, which are pathogenic in SLE. When given systemically, curli/DNA composites trigger immune activation and production of autoantibodies in lupus-prone and wild type mice. We also found that infection with curli-producing bacteria triggered higher autoantibody titers in lupus-prone mice compared to curli-deficient bacteria. These data provide a mechanism by which the microbiome and biofilm-producing enteric infections may contribute to the progression of SLE and point to a potential molecular target for treatment of autoimmunity. Cytokine dysregulation is also common in SLE patients. Serum cytokines are often elevated during active disease, including type I IFNs and IL-10. In chapter four we demonstrate that Il10 is a type I IFN response gene and has increased basal expression in dendritic cells (DCs) derived from pre-disease lupus-prone Sle1,2,3 mice. We show that Sle1,2,3-derived DCs overproduce IL-10 in response to TLR ligands and that this is the result of autocrine signaling though the type I IFN receptor (IFNAR). These results suggest that dysregulation of cytokine signaling in the myeloid compartment may contribute to IL-10 dysregulation in SLE. Renal disease remains a major cause of morbidity and mortality in SLE. A number of mouse models of chronic kidney disease have implicated the EGFR-family receptors in the progression of renal fibrosis and dysfunction. In chapter five we show that renal expression of ErbB2 is increased in murine lupus. We therefore asked if EGFR-family inhibition could prevent murine lupus nephritis. To test this possibility we used lapatinib, an EGFR-ErbB2 dual kinase inhibitor, in an IFN-accelerated model of murine lupus. We found that lapatinib administration lowered autoantibody levels but worsened renal disease. Lapatinib failure to treat murine lupus nephritis despite lowered autoantibody levels suggests EGFR-family signaling is required for tissue repair in the acute phase of kidney injury. Together this thesis clearly demonstrates the complexity of systemic autoimmune disease – bringing us to the crossroads of immunity and tolerance. The combination of both environmental triggers (e.g. bacterial infection) and genetic susceptibility (e.g. intrinsic cytokine dysregulation) leads to end organ damage (e.g. lupus nephritis). Here we sought to explore each aspect of disease progression in the hopes to develop better interventions for systemic autoimmune disease. / Microbiology and Immunology

Le lupus érythémateux disséminé (LED) est une maladie auto-immune chronique à forte composante inflammatoire pour laquelle il n’existe aucun traitement curatif. Les patients qui en sont atteints présentent une pléthore d’auto-anticorps, c’est-à-dire des anticorps reconnaissant des constituants normaux du soi, que le système immunitaire considère par erreur comme étrangers. La présence de ces anticorps mène à la formation de complexes immuns, dont les taux sériques élevés et les dépôts tissulaires détectés chez les personnes lupiques corrèlent avec l’activité de la maladie. Les complexes immuns favorisent également l’activation indue des cellules immunitaires, qui peuvent à leur tour contribuer aux dommages organiques observés chez plusieurs patients. Le neutrophile, une cellule clé de l’immunité innée pour laquelle des anomalies fonctionnelles et phénotypiques ont été soulevées dans le LED, interagit avec les complexes immuns via les récepteurs Fcgamma (FcgR). Le récepteur FcgRI, dont la présence à la surface des monocytes est positivement associée à des déterminants physiopathologiques importants du LED, est exprimé à des niveaux très faibles chez le neutrophile au repos, mais son expression est inductible en conditions d’infections sévères. La présente étude démontre que les HA-IgG, utilisés comme modèle de complexes immuns, entraînent presque instantanément une forte hausse de FcgRI à la surface des neutrophiles, et que la signalisation qui découle de ce récepteur est nécessaire à la production d’espèces réactives de l’oxygène. Ces molécules, normalement utilisées par les neutrophiles pour défendre l’organisme hôte contre les envahisseurs pathogènes, sont potentiellement dommageables pour les tissus sains. Nos travaux suggèrent que FcgRI est un contributeur important de la réponse des neutrophiles humains aux complexes immuns, et peuvent aider à expliquer le rôle délétère des neutrophiles dans les maladies auto-immunes comme le LED. / Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a strong inflammatory component and for which there is no cure. SLE patients have a plethora of autoantibodies, that is, antibodies that recognize normal constituents of the self, which the immune system mistakenly considers foreign. The presence of these antibodies leads to the formation of immune complexes, whose elevated serum levels and tissue deposits detected in patients with lupus correlate with the disease activity. Immune complexes also promote the undue activation of immune cells, which in turn can contribute to the organic damage seen in many patients. The neutrophil, a key cell of innate immunity for which functional and phenotypic abnormalities have been raised in SLE, interacts with immune complexes via Fc-gamma receptors (FcgR). The FcgRI receptor, whose presence on the surface of monocytes is positively associated with important pathophysiological determinants of SLE, is expressed at very low levels on the neutrophil at rest, but its expression is inducible under severe infections. The present study demonstrates that HA-IgGs, used as a model of immune complexes, almost instantly upregulate the expression of FcgRI on the surface of neutrophils, and that the signal ensuing of this receptor is necessary for the production of reactive oxygen species. These molecules, normally used by neutrophils to defend the host from pathogenic invaders, are potentially damaging to healthy tissue. Our work suggest FcgRI as an important contributor of the response of human neutrophils to immune complexes, and may help explain the deleterious role of neutrophils in autoimmune diseases like SLE.

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Two novel B cell populations were characterized in peripheral blood of patients with common variable immunodeficiency and healthy controls were observed using flow cytometry in the study supported by the grant IGA MZ ČR NKT11414-3. These B cell populations were defined as CD19+ CD27- CD21+ CD38low CD24+ IgM+ FO I and CD19+ CD27- CD21+ CD38low CD24++ IgM++ cells. Since none of found populations has ever been described, the aim of this thesis was to characterize these populations with focus on analysis of variable regions of the heavy chains of immunoglobulins and genes coding proteins participating in the process of VHDHJH formation (Rag 1, Rag 2, and TdT) produced by cells of these populations. Flow cytometry, single cell sorting, single-cell RT-PCR, IgVH, Rag 1, Rag 2, and TdT specific PCR amplification and cycle sequencing were employed to perform the molecular analysis in individual B lymphocytes. Both populations in two patients with common variable immunodeficiency, two healthy controls, and in two patients with autoimmune diseases - rheumatoid arthritis and systemic lupus erythematosus (as the disease control) - were examined. Finally, the statistical analysis was used to evaluate the differences in expression of variable regions of the heavy chains of immunoglobulins and in Rag1 and 2, and...