Molecular Basis for Overcoming Tolerance to Sm

系统性红斑狼疮（SLE）与自身反应性B细胞的失调有关。 当B细胞耐受性被克服并且对核抗原特异的细胞更新信号时，疾病发生 通过BCR转导导致自身抗体分泌。了解导致 并维持B细胞的无反应状态对于理解SLE的分子基础至关重要。在这 应用中，我们将测试的假设，即耐受Sm是克服时，抗原表位， 在凋亡细胞的膜泡上显示。我们认为这种独特的高度有序的 膜结合表位通过更新信号克服抗Sm B细胞中的部分无反应性状态 通过BCR进行转导。 Sm特异性B细胞（2-12/Vk 8 Dbl）发育为成熟的B2细胞，其显示活化的细胞表面 表型和不能分泌抗Sm抗体响应LPS。有趣的是，其他表型 与无反应性B细胞相关的变化在2- 12 Nk 8 Dbl B细胞中不存在，表明部分无反应性的状态。 无反应在目标1和2a中，我们将评估部分无反应性表型是否与不完全无反应性表型相关， BCR的脱敏，以及如果抗原显示更高效价的表位，如剪接体， Sm的四聚体或凋亡膜能够更新信号转导。机械地说， 当失敏受体重新分配到膜微区时，可能发生重新的信号转导 叫做脂筏。在目标2B中，我们将评估2-12/Vk 8 Dbl B细胞上的BCR是否从脂筏中排除 以及这些受体是否能够在被高价抗原连接后移位到筏上。 在目标3中，我们将使用体内模型评估凋亡细胞对Sm耐受性的影响。一是 将凋亡细胞注射到2-12/Vk 8Db 1小鼠中并评估是否可以克服对Sm的耐受性。中 第二种方法，我们将缺陷mer基因引入2-12/Vk 8 Db 1免疫球蛋白转基因小鼠中， 模型，并评估是否增加的凋亡细胞水平通过诱导Sm特异性 自身抗体

Dysregulation of autoreactive B cells has been implicated in systemic lupus erythematosus (SLE). Disease occurs when B cell tolerance is overcome and cells specific for nuclear antigens renew signal transduction through the BCR leading to autoantibody secretion. Understanding the mechanisms that induce and maintain an unresponsive state in B cells is crucial to understanding the molecular basis of SLE. In this application we will test the hypothesis that tolerance to Sm is overcome when antigenic epitopes are displayed on the membrane blebs of apoptotic cells. We propose that this unique display of highly ordered membrane-bound epitopes overcomes a state of partial anergy in anti-Sm B cells by renewing signal transduction through the BCR. Sm-specific B cells (2-12/Vk8 Dbl) develop into mature B2 cells that exhibit an activated cell surface phenotype and fail to secrete anti-Sm antibodies in response to LPS. Interestingly, other phenotypic changes associated with anergic B cells are absent in the 2-12Nk8 Dbl B cells suggesting a state of partial anergy. In aims 1 and 2a, we will assess if the partially anergic phenotype is associated with incomplete desensitization of the BCR and if antigens displaying higher valency epitopes, such as spliceosomes, tetramers of Sm, or apoptotic membranes, are capable of renewing signal transduction. Mechanistically, renewed signal transduction may occur when desensitized receptors repartition to membrane microdomains called lipid rafts. In aim 2b we will assess if the BCR on 2-12/Vk8 Dbl B cells are excluded from lipid rafts and if these receptors are capable of translocating to the rafts upon ligation by high valency antigens. In aim 3 we will assess the effect of apoptotic cells on tolerance to Sm using an in vivo model. First, we will inject apoptotic cells into the 2-12/Vk8 Dbl mice and assess if tolerance to Sm can be overcome. In a second approach, we will introduce a defective mer gene into the 2-12/Vk8 Dbl immunoglobulin transgenic model and assess if increased levels of apoptotic cells overcome tolerance by inducing Sm-specific autoantibodies