IG CLASS SWITCHING IN LUPUS B CELLS

狼疮 B 细胞中的 IG 类转换

• 批准号: 6044320
• 负责人: Paolo Casali
• 金额: $ 29.6万
• 依托单位: WEILL MEDICAL COLL OF CORNELL UNIV
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-01 至 2005-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6044320
• 关键词: B lymphocyte; CD antigens; CD40 molecule; antibody formation; autoantibody; biological signal transduction; clinical research; gene rearrangement; genetic polymorphism; genetic regulatory element; human subject; immunoglobulin D; immunoglobulin G; immunoglobulin M; immunoglobulin genes; interferon gamma; interleukin 10; interleukin 4; systemic lupus erythematosus; transforming growth factors

The long term goal of this proposal is to gain insight into the mechanisms underlying the generation of autoantibodies in systemic lupus erythematosis (SLE), a major human autoimmune disease. The predominant and pathogenic anti-self response in these autoimmune patients consists of autoantibodies to nuclear components, including DNA. The origin of these autoantibodies remains enigmatic, but antibodies with similar binding activity are expressed by the normal B cell repertoire (natural autoantibodies). Compared to naturally occurring anti-DNA autoantibodies, lupus autoantibodies of similar specificity are "affinity mature", i.e., they are somatically mutated and antigen-selected. In addition, while the former are IgM, the latter are in general IgG, suggesting that class switching, a crucial mechanism in the maturation of any antibody response, is also important in the generation of autoantibodies in SLE. In class switching to IgG, the constant (C) region of the mu H chain is replaced by Cgamma region, resulting in the acquisition of novel biological activities, including the ability to pass into the extravascular space, and, therefore, in the case of autoantibodies to produce tissue damage. IgG-switched B cells are numerous in the circulation of SLE patients, and IgG accounts for the majority of the pathogenic autoantibodies in these patients. We formally argue here that class switching to IgG occurs more frequently and more effectively in lupus mu+ B cells than in normal mu" B cells. We further argue that this enhanced IgM->IgG switching results from a higher expression of CD40L by lupus T and B cells, as well as from a higher switching propensity of the B cells of these patients, due to a polymorphism of the Cgamma gene promoter or switch regions, and/or to dysregulation of the CD30-dependent mechanism that, as we have recently shown, physiologically dampens IgG-inducing stimuli. To test our hypothesis, we propose: (i) to study CD40L expression in SLE B cells, and their capacity to promote switching to IgG hypothesis, we propose: (i) to study CD40L expression in SLE B cells, and their capacity to promote switching to IgG using our unique in vitro human monoclonal (CL-01) IgM+ IgD+ B cell system; (ii) to analyze the in vitro spontaneous and CD40:CD40-induced IgG class switching in SLE IgM+ IgD+ B cells; (iii) to analyze the regulatory regions upstream of the Cgamma1, Cgamma2, Cgamma3, and Cgamma4 genes in SLE patients, their family members, and for comparison healthy subjects; and finally, (iv) to analyze the down-regulation of the CD40-mediated Ig class switching by CD30, another cell surface molecule of the TNFR family, and the interference with this mechanism by soluble CD30. The proposed experiments should further our understanding of the means that lead to Ig class switching and generation of IgG autoantibodies in lupus, and may help design specific means of therapeutic intervention.

该提案的长期目标是深入了解系统性红斑狼疮（SLE）的自身抗体产生的机制，这是一种主要的人类自身免疫性疾病。这些自身免疫性患者中的主要和致病性抗自身反应包括对包括DNA在内的核成分的自身抗体。这些自身抗体的起源仍然是神秘的，但是具有相似结合活性的抗体由正常的B细胞库（天然自身抗体）表达。与天然存在的抗DNA自身抗体相比，具有相似特异性的狼疮自身抗体是“亲和力成熟”，即它们是体形突变和抗原选择的。此外，虽然前者是IgM，但后者通常是IgG，这表明类转换是任何抗体反应成熟的关键机制，在SLE中的自身抗体的产生中也很重要。在切换到IgG的类中，MU H链的常数（C）区域被Cgamma区域取代，从而获得了新型生物学活性，包括进入血管外空间，因此，在自身抗体的情况下，可以产生组织损伤。在SLE患者的循环中，IgG开关的B细胞很多，IgG占这些患者的大部分致病自身抗体。 We formally argue here that class switching to IgG occurs more frequently and more effectively in lupus mu+ B cells than in normal mu" B cells. We further argue that this enhanced IgM->IgG switching results from a higher expression of CD40L by lupus T and B cells, as well as from a higher switching propensity of the B cells of these patients, due to a polymorphism of the Cgamma gene promoter or switch regions,正如我们最近所表明的那样，在生理上抑制了IgG诱导刺激以检验我们的假设，我们提出：（i）研究SLE B细胞中的CD40L表达，并促进IGG的能力来促进CD40，/否体外人单克隆（CL-01）IgM+ IgD+ B细胞系统；他们的家人，并为了比较健康的主题；最后，（iv）分析CD30，TNFR家族的另一个细胞表面分子的CD40介导的Ig类切换的下调，以及可溶性CD30对这种机制的干扰。提出的实验应进一步了解狼疮中IG类转换和IgG自身抗体的产生的手段，并可能有助于设计特定的治疗干预手段。