Regulation of the anti-phospholipid response in SLE

描述(申请人提供)：这项建议的目标是确定B细胞对磷脂耐受性丧失的机制，以及抗磷脂抗体对同时发展为增殖性肾小球肾炎和抗磷脂综合征的NZW/BXSB F1(W/B)小鼠的组织损伤机制。携带包含TLR7基因重复的YaA基因的雄性W/B小鼠的疾病会加速。我们已经证明，T细胞的帮助对于抗磷脂B细胞的初始激活和高亲和力的免疫球蛋白自身抗体的诱导是必需的。我们的建议基于以下假设：1)TLR7的过表达改变了B细胞选择或B细胞激活阈值，从而使NAOVE B细胞更容易激活T细胞，而T细胞是疾病启动和产生类切换自身抗体所必需的。2)免疫复合物的形成和免疫球蛋白抗磷脂抗体对凋亡颗粒的调理作用导致核酸被运送到含有内小体的TLR。TLRs的参与既诱导了促进浆细胞成熟的IFN1，也诱导了增强B细胞存活和类别转换的BAFF；然后，疾病可以通过T细胞无关的机制传播，这种机制在携带过多TLR7的男性中尤为突出。由于过量的IFN1产生是SLE的一个特征，并且IFN1诱导TLR7的上调，特别是在女性中，尽管在SLE患者中没有发现遗传的TLR7过表达，但类似的机制可能适用于具有干扰素签名的个体。为了解决这些假设，我们将使用具有自身反应的转基因重链的小鼠，并在B细胞发育途径的连续阶段检查B细胞的选择。这一策略将使我们能够研究B细胞信号的内在变化、来自先天免疫系统的外源性信号和T细胞在最初对自身抗原的耐受性丧失和抗磷脂反应的持久中的作用。我们的数据还将有助于确定抗磷脂综合征对传统免疫抑制疗法无效的原因，并有助于提出治疗这种毁灭性综合征的新策略。我们的第三个假设是，致病自身抗体本身可以引起由Fc受体或补体依赖机制介导的抗磷脂综合征的表现，但血栓的形成需要其他炎症介质激活内皮。我们将检验这一“二次打击”的机制之一是通过神经酰胺途径介导内皮细胞死亡的假说。我们的长期目标是确定导致抗磷脂综合征诱导和传播的关键途径之间的相互作用，以便最好地为SLE患者设计个性化的治疗方法。

DESCRIPTION (provided by applicant): The goal of this proposal is to determine the mechanisms for loss of B cell tolerance to phospholipids and mechanisms for tissue damage by anti-phospholipid antibodies in NZW/BXSB F1 (W/B) mice that develop both proliferative glomerulonephritis and anti-phospholipid syndrome. Disease is accelerated in male W/B mice that carry the Yaa locus containing a reduplication of the TLR7 gene. We have shown that T cell help is required for initial activation of anti-phospholipid B cells and induction of high affinity IgG autoantibodies. Our proposal is based on the following hypotheses: 1) Over-expression of TLR7 alters either B cell selection or B cell activation threshold, thus rendering naove B cells more prone to the T cell activation that is required for disease initiation and production of clas switched autoantibodies. 2) Immune complex formation and opsonization of apoptotic particles by IgG anti-phospholipid antibodies results in delivery of nucleic acids to TLR containing endosomes. Engagement of TLRs induces both IFN1 that fosters plasma cell maturation and BAFF that enhances B cell survival and class switching; disease can then be propagated by T cell independent mechanisms that are prominent in males bearing excess TLR7. Because excess IFN1 production is a feature of SLE and IFN1 induces upregulation of TLR7, particularly in females, similar mechanisms may pertain in individuals with the IFN signature even though genetic TLR7 overexpression has not been found in humans with SLE. To address these hypotheses, we will use mice with an autoreactive transgenic heavy chain and examine B cell selection at sequential stages of the B cell developmental pathway. This strategy will allow us to examine the role of intrinsic alterations in B cell signaling, exogenous signals from the innate immune system and T cell help in the initial loss of tolerance to autoantigens and in the perpetuation of the anti- phospholipid response. Our data will also help determine why anti-phospholipid syndrome fails to respond to conventional immunosuppressive therapies and help suggest new strategies for treating this devastating syndrome. Our third hypothesis is that pathogenic autoantibodies alone can cause the manifestations of the anti- phospholipid syndrome that are mediated by Fc receptor or complement dependent mechanisms but that the formation of thromboses requires other inflammatory mediators to activate the endothelium. We will test the hypothesis that one mechanism for this "second hit" is endothelial cell death mediated via the ceramide pathway. Our long term goal is to define the interactions of the crucial pathways that contribute to induction and propagation of the anti-phospholipid syndrome so as to best devise individualized therapies for patients with SLE.