Regulation of the anti-phospholipid response in SLE

描述（由申请人提供）：本提案的目的是确定发生增生性肾小球肾炎和抗磷脂综合征的NZW/BXSB F1 （W/B）小鼠B细胞对磷脂耐受性丧失的机制和抗磷脂抗体对组织损伤的机制。携带含有TLR7基因重复的Yaa位点的雄性W/B小鼠的疾病加速。我们已经证明，T细胞的帮助是必需的抗磷脂B细胞的初始激活和诱导高亲和力的IgG自身抗体。我们的建议基于以下假设：1)TLR7的过表达改变了B细胞的选择或B细胞的激活阈值，从而使原始B细胞更容易激活T细胞，这是疾病启动和产生类转换自身抗体所必需的。2)免疫复合物的形成和凋亡颗粒被IgG抗磷脂抗体调理，导致核酸传递到含有TLR的核内体。参与TLRs诱导IFN1促进浆细胞成熟和BAFF提高B细胞存活和类别转换；然后，疾病可以通过与T细胞无关的机制传播，这种机制在携带过量TLR7的男性中很突出。由于过量的IFN1产生是SLE的一个特征，而IFN1诱导TLR7上调，尤其是在女性中，因此类似的机制可能适用于具有IFN特征的个体，尽管在SLE患者中未发现遗传性TLR7过表达。为了解决这些假设，我们将使用具有自反应性转基因重链的小鼠，并在B细胞发育途径的顺序阶段检查B细胞选择。这一策略将允许我们检查B细胞信号的内在改变的作用，来自先天免疫系统和T细胞的外源性信号有助于对自身抗原耐受的初始丧失和抗磷脂反应的延续。我们的数据还将有助于确定为什么抗磷脂综合征对常规免疫抑制疗法无效，并有助于提出治疗这种破坏性综合征的新策略。我们的第三个假设是病原性自身抗体单独可以引起由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来激活内皮。我们将检验这种“二次打击”的一种机制是通过神经酰胺途径介导的内皮细胞死亡的假设。我们的长期目标是确定诱导和传播抗磷脂综合征的关键途径的相互作用，以便为SLE患者设计最佳的个体化治疗。

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.