Somatic Hypermutation in SLE

SLE 中的体细胞超突变

• 批准号: 8246151
• 负责人: Lawrence J Wysocki
• 金额: $ 39.63万
• 依托单位: NATIONAL JEWISH HEALTH
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-12-01 至 2016-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8246151
• 关键词: Address; Adult; Affinity; Antibodies; Antigens; Area; Autoantibodies; Autoantigens; Autoimmune Diseases; Autoimmunity; Avidity; B-Lymphocytes; Binding; Bone Marrow; CD4 Positive T Lymphocytes; Cells; Chimera organism; DNA Nucleotidylexotransferase; Data; Development; Disease; Gene Expression; Gene Targeting; Generations; Genes; Genetic; Genetic Polymorphism; Goals; Immune; Immune response; Immunoglobulin Genes; Immunoglobulin Somatic Hypermutation; Investigation; Knowledge; Lead; Lupus Erythematosus; Lymphopoiesis; Modeling; Molecular Target; Mus; Mutate; Mutation; Natural History; Nuclear; Nuclear Antigens; Nucleotides; Participant; Physiological; Play; Prevalence; Process; Recruitment Activity; Reporting; Research; Research Personnel; Resources; Role; Scleroderma; Self Tolerance; Serum; Sjogren' s Syndrome; Somatic Mutation; Source; Specific qualifier value; Specificity; Systemic Lupus Erythematosus; T-Lymphocyte; Testing; Thyroiditis; Time; Tissues; activation-induced cytidine deaminase; anti-IgG; autoreactive B cell; autoreactivity; founder mutation; mouse model; mutant; prevent; research study; systemic autoimmune disease; tool

DESCRIPTION (provided by applicant): Anti-nuclear antibodies (ANA) are a hallmark of systemic autoimmunity and of lupus erythematosus (SLE) in particular. Due to their prevalence in disease and specificity for ubiquitous self-antigens that normally induce self-tolerance, they have been the subjects of extensive investigation into mechanisms that lead to breaches in B cell self-tolerance during autoimmunity. Defining the origin of such antibodies, however, has proved to be problematic. This is because of germline sequence polymorphisms in Ig V region genes and because of extensive somatic diversity generated by processes that assemble V region genes during B lymphopoiesis in the bone marrow and that mutate them in the periphery during immune responses. To determine the origin of ANA, we developed a unique mouse model of spontaneous SLE in which V region gene expression by autoreactive B cells could be clearly defined and in which all somatic mutations could be unequivocally identified. In B6.Nba2 Tdt-/- Igh Igk mice, the absence of terminal deoxynucleotidyl transferase (Tdt) enabled us to identify every somatic mutation, even in CDR3, where untemplated addition of nucleotides during V gene assembly would otherwise obscure them. By reverting somatic mutations to germline sequence in spontaneous ANA-producing clones, we found in preliminary studies that almost all of the ANA originated from nonautoreactive antecedent B cells that acquired their autoreactivity via the process of somatic hypermutation (SHM). This finding leads us to hypothesize that activation-induced cytidine deaminase (AID) plays a paramount role in generating ANA of systemic autoimmune disease. In this application, we propose to test this "mutation-founder" hypothesis and its implications. We will use AID-deficient mice to determine if it applies to systemic autoimmunity in other spontaneous models of SLE and to specific types of ANA. We will determine if the requirement for T cell help in SLE, reported by numerous investigators, is explained solely by its role in generating the mutant autoreactive B cells or whether T cell help is also required after the mutant clones arise. Germline revertant nonautoreactive antibodies will be used as probes to define natural immunogens that recruited precursors to the ANA-producing mutant clones. We will develop a new model of tolerance in germline ANA-specific B cells and will determine whether mutant ANA generated by AID promote the escape of germline ANA-producing B cells by obscuring or removing nuclear antigens that would otherwise render the B cells tolerant. Our preliminary studies provide us with unique tools and information to address these issues. Results of this project will provide basic information about the natural history of autoreactive B cells, which is essential if we are to understand, control and prevent systemic autoimmune disease. PUBLIC HEALTH RELEVANCE: B lymphocytes that produce autoantibodies directed against self-tissues are major participants in autoimmune diseases such as systemic lupus erythematosus (SLE), scleroderma, Sjogren's syndrome and thyroiditis. A major goal of research in autoimmunity is to understand how such cells evade self-tolerance checkpoints that normally silence them functionally or physically under physiological circumstances. Progress in this area has been hampered by a lack of basic information regarding where these disease-participating cells arise and how they gain autoreactivity in the first place. Conventional wisdom holds that they first express autoantibodies when they are "born" in the adult bone marrow. But our preliminary data indicate that the autoantibodies of pathological B cells are created later in secondary tissues by mutation in the genes that specify the antibodies. In this study, we propose to test this basic hypothesis, define the disease-associated autoantibodies to which it applies and test prior interpretations regarding escape of such cells in autoimmune disease. By pinpointing the origin of autoreactive B cells and defining requirements for their progression in disease, we will establish a framework of knowledge that is essential to defining molecular targets for therapy and strategies to control or prevent systemic autoimmune disease.

描述（由申请人提供）：抗核抗体（ANA）是系统性自身免疫性疾病，特别是红斑狼疮（SLE）的标志。由于它们在疾病中的普遍性以及对通常诱导自我耐受的普遍存在的自身抗原的特异性，它们已成为在自身免疫过程中导致 B 细胞自我耐受破坏的机制广泛研究的对象。然而，确定此类抗体的起源已被证明是有问题的。这是因为 Ig V 区基因中的种系序列多态性，以及在骨髓 B 淋巴细胞生成过程中组装 V 区基因的过程产生的广泛体细胞多样性，以及在免疫反应过程中在外周使它们突变的过程所产生的广泛体细胞多样性。为了确定 ANA 的起源，我们开发了一种独特的自发性 SLE 小鼠模型，其中可以清楚地定义自身反应性 B 细胞的 V 区基因表达，并且可以明确地识别所有体细胞突变。在 B6.Nba2 Tdt-/- Igh Igk 小鼠中，末端脱氧核苷酸转移酶 (Tdt) 的缺失使我们能够识别每个体细胞突变，甚至在 CDR3 中，在 V 基因组装过程中未模板化的核苷酸添加会掩盖它们。通过将体细胞突变恢复为自发产生 ANA 的克隆中的种系序列，我们在初步研究中发现，几乎所有 ANA 都起源于非自身反应性的先行 B 细胞，这些 B 细胞通过体细胞超突变 (SHM) 过程获得了自身反应性。这一发现使我们推测，激活诱导的胞苷脱氨酶 (AID) 在系统性自身免疫性疾病的 ANA 生成中发挥着至关重要的作用。在本申请中，我们建议测试这种“突变创始人”假设及其含义。我们将使用 AID 缺陷小鼠来确定它是否适用于其他自发性 SLE 模型中的系统性自身免疫以及特定类型的 ANA。我们将确定许多研究人员报告的 SLE 中 T 细胞帮助的需要是否仅由其在产生突变自身反应性 B 细胞中的作用来解释，或者在突变克隆出现后是否也需要 T 细胞帮助。种系回复非自身反应性抗体将用作探针来定义天然免疫原，该免疫原招募产生 ANA 的突变克隆的前体。我们将在种系 ANA 特异性 B 细胞中开发一种新的耐受模型，并将确定 AID 产生的突变 ANA 是否通过掩盖或去除核抗原来促进产生种系 ANA 的 B 细胞的逃逸，否则这些核抗原会使 B 细胞产生耐受。我们的初步研究为我们提供了解决这些问题的独特工具和信息。该项目的结果将提供有关自身反应性 B 细胞自然史的基本信息，这对于我们了解、控制和预防系统性自身免疫性疾病至关重要。 公共健康相关性：产生针对自身组织的自身抗体的 B 淋巴细胞是系统性红斑狼疮 (SLE)、硬皮病、干燥综合征和甲状腺炎等自身免疫性疾病的主要参与者。自身免疫研究的一个主要目标是了解这些细胞如何逃避自我耐受检查点，这些检查点通常在生理情况下使它们在功能上或身体上保持沉默。由于缺乏有关这些疾病参与细胞的产生位置以及它们如何获得自身反应性的基本信息，该领域的进展受到阻碍。传统观点认为，当它们在成人骨髓中“出生”时，它们首先表达自身抗体。但我们的初步数据表明，病理性 B 细胞的自身抗体是后来通过特定抗体的基因突变在次生组织中产生的。在这项研究中，我们建议检验这一基本假设，定义其适用的与疾病相关的自身抗体，并检验先前关于此类细胞在自身免疫性疾病中逃逸的解释。通过查明自身反应性 B 细胞的起源并确定其疾病进展的要求，我们将建立一个知识框架，这对于确定治疗的分子靶点以及控制或预防系统性自身免疫性疾病的策略至关重要。