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的标志，尤其是狼疮的红斑（SLE）。由于它们在通常会引起自我耐受性的无处不在的自我抗原方面的特异性和特异性，因此，它们一直是对导致自身免疫期间B细胞自我耐受性违反的机制进行广泛研究的主题。但是，定义这种抗体的起源已被证明是有问题的。这是因为Ig V区域基因中的种系序列多态性，以及由骨髓中B淋巴细胞组合V区基因的过程产生的广泛的体细胞多样性，并在免疫反应过程中将它们突变为外周中。为了确定ANA的起源，我们开发了一种独特的自发SLE小鼠模型，在该模型中，可以清楚地定义自动反应性B细胞的V区域表达，并且可以明确鉴定所有体细胞突变。在B6.NBA2 TDT - / - IGK小鼠中，缺乏末端脱氧核苷酸转移酶（TDT）使我们能够识别每个体细胞突变，即使在CDR3中，在CDR3中，在V基因组装过程中未添加核苷酸的核苷酸也会掩盖它们。通过将体细胞突变恢复为自发性ANA产生的克隆的种系序列，我们在初步研究中发现，几乎所有的ANA源自非抗反应性前B细胞，这些B细胞通过体细胞超成熟（SHM）的过程获得了其自动反应性。这一发现使我们假设激活诱导的胞苷脱氨酶（AID）在产生系统性自身免疫性疾病的ANA中起着至关重要的作用。在此应用中，我们建议检验此“突变创始人”假设及其含义。我们将使用缺乏辅助的小鼠来确定它是否适用于其他自发模型的SLE和特定类型的ANA的全身自身免疫性。我们将确定众多研究人员报告的T细胞帮助的需求是否仅是由于其在产生突变体自动反应性B细胞中的作用，还是突变克隆出现后是否也需要T细胞帮助。种系恢复非运动反应性抗体将用作定义自然免疫原子的探针，该抗体将前体募集到ANA产生的突变克隆。我们将在种系ANA特异性B细胞中开发一种新的耐受性模型，并确定通过辅助产生的突变体ANA是否通过遮盖或去除否则会呈现B细胞的核抗原来促进生殖产生的B细胞的逃脱。我们的初步研究为我们提供了独特的工具和信息来解决这些问题。该项目的结果将提供有关自动反应性B细胞自然史的基本信息，如果我们要理解，控制和预防系统性自身免疫性疾病，这至关重要。 公共卫生相关性：产生针对自我组织的自身抗体的B淋巴细胞是自身免疫性疾病的主要参与者，例如全身性狼疮红斑（SLE），硬皮病，Sjogren's综合征和甲状腺炎。自身免疫性研究的主要目标是了解这些细胞通常在生理环境下通常在功能或物理上在功能或物理上沉默它们的自我耐受检查点。缺乏有关这些参与疾病的细胞以及它们如何获得自动反应性的基本信息，这一领域的进展受到了阻碍。传统观念认为，当他们在成年骨髓中“出生”时，它们首先表达自身抗体。但是我们的初步数据表明，病理B细胞的自身抗体是通过指定抗体的基因中的突变在二级组织中产生的。在这项研究中，我们建议检验这一基本假设，定义与疾病相关的自身抗体，并测试有关此类细胞在自身免疫性疾病中逃脱的先前解释。通过确定自动反应性B细胞的起源并定义其在疾病中进展的要求，我们将建立一个知识框架，这对于定义治疗和控制或预防系统性自身免疫性疾病的策略至关重要。