Immune Dysregulation in HIT

HIT 中的免疫失调

• 批准号: 7815711
• 负责人: Gowthami M Arepally
• 金额: $ 1.93万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7815711
• 关键词: Animal Model; Animals; Antibodies; Antibody Formation; Antibody Specificity; Antigen-Presenting Cells; Antigens; Antiphospholipid Syndrome; Autoantigens; Autoimmune Process; Biological; Blood Platelets; C57BL/6 Mouse; CD4 Positive T Lymphocytes; Cell surface; Clinical; Complex; Data; Dependence; Disease; Dose; Drug Hypersensitivity; Employee Strikes; Glycosaminoglycans; Helper-Inducer T-Lymphocyte; Heparin; Immune; Immune System Diseases; Immune response; Immunologic Memory; Immunologics; In Vitro; Inbred BALB C Mice; Incidence; Injury; Knowledge; Lead; Life; Lymphocyte; Macromolecular Complexes; Megakaryocytes; Memory; Modeling; Mus; Nature; Pattern; Pattern recognition receptor; Penicillins; Peripheral; Pharmaceutical Preparations; Platelet Activation; Platelet Factor 4; Play; Property; Quinine; Research Personnel; Role; Self Tolerance; Serological; Signal Transduction; Source; Specificity; Stimulus; Systemic Lupus Erythematosus; T-Cell Activation; T-Lymphocyte; TNFSF5 gene; Testing; Therapeutic Intervention; Thrombocytopenia; Thrombotic Thrombocytopenic Purpura; Translating; Ursidae Family; antigen challenge; autoreactive T cell; base; immunogenic; immunogenicity; in vivo; insight; prevent; response

DESCRIPTION (provided by applicant): Heparin-lnduced Thrombocytopenia (HIT) is a life-threatening thrombotic illness caused by drug-dependent antibodies directed to complexes of Platelet Factor 4 (PF4) and heparin. Although HIT, by definition, is a drug-induced disorder, its immunologic features bear little resemblance to other commonly encountered drug allergies, like quinine or penicillin. Unlike most drug-dependent immune responses, which are idiosyncratic and long-lived, the antibody response to heparin displays dose dependence, is short-lived and may lack immune memory. Based on these atypical features of the antibody response to drug, as well as known antibody specificities towards self-antigens (PF4 and endogenous glycosaminoglycans) in HIT, we posit that HIT is a T-cell dependent immune disorder in which self-tolerance is transiently dysregulated. Specifically, we hypothesize that HIT arises from a breach in self-tolerance brought about by immunostimulatory signals (involving antigenic PF4/heparin complexes and platelet CD154) and impaired immunoregulatory mechanisms. To test this hypothesis, we have developed a murine autoimmune model in which PF4/heparin antibodies (anti-mP+H) arise de novo after antigen challenge. In preliminary studies, we show that anti-mPF4/heparin from these animals recapitulate key aspects of the HIT immune response, including its variable incidence, serologic specificities and functional properties. We also show that mPF4/heparin antibody production in animals requires CD4+ T-helper cells and that immune recall is variably expressed in BALB/c and C57BL/6 mice. Using this animal model, we will: 1) Demonstrate cellular activation by macromolecular PF4/heparin complexes. In this aim, we will perform in vitro and in vivo studies to delineate lymphocyte responses to antigen and demonstrate that mPF4/heparin complexes trigger APC activation. 2) Delineate the role of platelet activation and platelet CD154 (Cp40L) in induction of the HIT immune response. Our preliminary studies indicate that in vivo platelet activation induces PF4/heparin antibody production. We hypothesize that platelet activation is essential for immune initiation in HIT, as activated platelets provide both a source of antigen (PF4) and co-stimulatory signals (CD154) needed for antibody production. To test this hypothesis, we will examine the sensitizing effects of platelet activation, mPF4 and platelet CD154 on the HIT immune response. 3) Delineate impaired immunoregulatory mechanisms in the murine immune response to PF4/heparin. Our preliminary studies show striking differences in patterns of immune recall in BALB/c and C57BL/6 mice that suggest differences in immunoregulatory function in animals. In this aim, we will test our hypothesis that regulatory T cells play a critical role in defining the course of immune response in HIT. It is expected that these studies will lead to insights into strategies that prevent or modulate immune complications from this life-threatening thrombotic disorder.

描述（由申请人提供）： 肝素诱导的血小板减少症 (HIT) 是一种危及生命的血栓性疾病，由针对血小板因子 4 (PF4) 和肝素复合物的药物依赖性抗体引起。尽管根据定义，HIT 是一种药物引起的疾病，但其免疫学特征与其他常见的药物过敏（如奎宁或青霉素）几乎没有相似之处。与大多数特殊且长期的药物依赖性免疫反应不同，对肝素的抗体反应表现出剂量依赖性，是短暂的并且可能缺乏免疫记忆。基于抗体对药物反应的这些非典型特征，以及已知的 HIT 中针对自身抗原（PF4 和内源性糖胺聚糖）的抗体特异性，我们认为 HIT 是一种 T 细胞依赖性免疫性疾病，其中自我耐受暂时失调。具体来说，我们假设 HIT 是由免疫刺激信号（涉及抗原 PF4/肝素复合物和血小板 CD154）和受损的免疫调节机制引起的自我耐受性破坏引起的。为了检验这一假设，我们开发了一种小鼠自身免疫模型，其中 PF4/肝素抗体（抗 mP+H）在抗原攻击后从头产生。在初步研究中，我们表明这些动物的抗 mPF4/肝素概括了 HIT 免疫反应的关键方面，包括其可变的发生率、血清学特异性和功能特性。我们还表明，动物中 mPF4/肝素抗体的产生需要 CD4+ T 辅助细胞，并且免疫回忆在 BALB/c 和 C57BL/6 小鼠中表达不同。使用该动物模型，我们将： 1) 展示大分子 PF4/肝素复合物的细胞激活作用。为此，我们将进行体外和体内研究，以描绘淋巴细胞对抗原的反应，并证明 mPF4/肝素复合物触发 APC 激活。 2) 描述血小板活化和血小板 CD154 (Cp40L) 在诱导 HIT 免疫反应中的作用。我们的初步研究表明体内血小板活化诱导 PF4/肝素抗体产生。我们假设血小板活化对于 HIT 中的免疫启动至关重要，因为活化的血小板提供抗体产生所需的抗原 (PF4) 来源和共刺激信号 (CD154)。为了检验这一假设，我们将检查血小板活化、mPF4 和血小板 CD154 对 HIT 免疫反应的敏化作用。 3) 描述小鼠对 PF4/肝素的免疫反应中受损的免疫调节机制。我们的初步研究表明 BALB/c 和 C57BL/6 小鼠的免疫回忆模式存在显着差异，这表明动物之间的免疫调节功能存在差异。为此，我们将检验我们的假设，即调节性 T 细胞在定义 HIT 免疫反应过程中发挥着关键作用。预计这些研究将有助于深入了解预防或调节这种危及生命的血栓性疾病的免疫并发症的策略。