B cell responses in heparin-induced thrombocytopenia

肝素诱导的血小板减少症(HIT)可能是最常见的药物诱导的免疫疾病， 可导致毁灭性或致命性的动/静脉血栓形成和血栓栓塞症。患者的免疫球蛋白抗体 与肝素形成免疫复合物中的血小板因子4(PF4)形成IgG/PF4/肝素免疫复合物 是HIT发病机制的核心。这些免疫复合体依次与血小板表面的FcyRlla结合，并 诱导血小板活化，导致血小板减少并导致血栓形成。Hit展示了这两种情况 T-CEW非依赖性免疫反应的特征，以抗体的快速出现和下降为特征 没有免疫记忆，以及次级T-CEW依赖的免疫反应的一些方面， 特点是流行的抗PF4/肝素抗体的Ig G类和对T细胞的要求。 HIT的这些非典型免疫学特征扰乱了我们对其发病机制的理解 哪些B细胞参与了该病的免疫发病机制。已知来自B细胞的信号 受体(BCR)是B细胞功能所必需的。BCR信号中的一个关键事件是磷脂酶的激活 Cy2(PLCy2)，它能水解膜脂生成二酰甘油(DAG)和肌醇1，4，5- 三磷酸(IP3)。DAG导致激活一条涉及蛋白激酶C(PKC)的信号通路， B细胞淋巴瘤10(Bcl10)-包含复合体，以及蛋白激酶TAK1。我们之前的目标是 基因阻断研究表明，PLCy2/Bcl10/TAK1通路对于bcr介导的信号转导是必不可少的。 抗体的产生。此外，一种产生抗小鼠PF4/肝素HIT抗体的小鼠模型已经 已经建立，以及hFcyRlla转基因小鼠，可以重述HIT。这些模型使它成为 可以表征对PF4/肝素复合体的免疫反应的分子方面 对人类发展至关重要。我们建议将这些小鼠模型与几个 其他转基因小鼠品系，以阐明B细胞如何产生PF4/肝素特异性抗体 并决定是否操纵PLCy2/Bcl10/TAK1通路来控制B细胞 抗体的产生可以预防HIT。具体地说，我们将确定1)边缘带的贡献，B1 和记忆B细胞攻击抗体的产生，2)B细胞无能的崩溃是否有助于 3)抑制PLCy2/Bcl10/TAK1通路是否可以 防止命中。确定负责产生HIT抗体的B细胞亚群，确定PF4如何 /肝素特异性B细胞被激活，并确定BCR信号通路在HIT抗体中的作用 研究结果将为HIT的发病机制提供新的线索，并有助于开发新的预防方法。 相关性(请参阅说明)： 这项研究旨在了解肝素引起的血小板减少症的原因，这是最常见的 药物引起的危及生命的血液疾病，并有望确定开发新型药物的具体目标 以及控制和预防该病的有效方法。

Heparin-induced thrombocytopenia (HIT) may be the most common drug-induced immune disease, and can result in devastating or fatal arterial/venous thrombosis and thromboembolism. Patient IgG antibodies that bind to platelet factor 4 (PF4) in a complex with heparin to form lgG/PF4/heparin immune complexes are central to the pathogenesis of HIT. These immune complexes, in turn, bind FcyRlla on the platelet surface and induce platelet activation, leading to thrombocytopenia and contributing to thrombosis. HIT exhibits both features of a T ceW-independent immune response, characterized by the rapid onset and decline of antibodies and no immunological memory, as well as aspects of a secondary T ceW-dependent immune response, characterized by the prevalence of the IgG class of anti-PF4/heparin antibodies and a requirement for T cells. These atypical immunological characteristics of HIT have confounded our understanding ofthe mechanism by which B cells contribute to the immune pathogenesis of the disease. It is known that signals from the B cell receptor (BCR) are required for B cell function. A critical event in BCR signaling is activation of phospholipase Cy2 (PLCy2), which hydrolyzes membrane lipids to generate diacylglycerol (DAG) and inositol 1,4,5- trisphosphate (IP3). DAG leads to activation of a signaling pathway that involves protein kinase C (PKC), a B-cell lymphoma 10 (BcllO)-containing complex, and the protein kinase TAK1. Our previous targeted gene-disruption studies have shown that the PLCy2/Bcl10/TAK1 pathway is essential for BCR-mediated antibody production. Moreover, a mouse model for production of anti-mouse PF4/heparin HIT antibodies has been established, as well as hFcyRlla transgenic mice that can recapitulate HIT. These models make it possible to characterize molecular aspects of the immune response to PF4/heparin complexes that are essential to human HIT development. We propose to use these mouse models, in combination with several other genetically-modified mouse strains, to elucidate how B cells produce the PF4/heparin-specific antibodies that cause HIT, and determine whether manipulation of the PLCy2/Bcl10/TAK1 pathway to control B cell antibody production can prevent HIT. Specifically, we will determine 1) the contribution of marginal zone, B1 and memory B cells to HIT antibody production, 2) whether breakdown of B cell anergy contributes to activation of PF4/heparin-specific B cells, and 3) whether inhibition of the PLCy2/Bcl10/TAK1 pathway can prevent HIT. Identifying the B cell subsets responsible for HIT antibody production, determining how PF4 /heparin-specific B cells are activated, and defining the role of the BCR signaling pathway in HIT antibody production will provide new clues to the pathogenesis of HIT and help to develop novel prevention methods. RELEVANCE (See instructions): This study aims to understand the cause of heparin-induced thrombocytopenia, one of the most common drug-induced life-threatening blood diseases, and is expected to identify specific targets for developing novel and effective ways for the control and prevention of this disease.