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 - 肝素诱导的血小板减少症（HIT）是一种威胁生命的血栓性疾病，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。尽管从定义上看，命中率是一种药物诱导的疾病，但其免疫学特征与其他常见的药物过敏，例如奎宁或青霉素几乎没有相似之处。与大多数药物依赖性免疫反应（具有特质且寿命长）不同，对肝素的抗体反应显示剂量依赖性，是短暂的，可能缺乏免疫记忆。基于对药物的抗体反应的这些非典型特征，以及对自我抗原的已知抗体特异性（PF4和内源性糖胺聚糖），我们认为HIT是一种hIT是一种T细胞依赖性免疫疾病，其中自耐自我耐受性是短暂失调的。具体而言，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）和免疫调节机制受损的自我耐受性引起的。为了检验这一假设，我们开发了一种鼠自身免疫性模型，其中PF4/肝素抗体（抗MP+H）在抗原挑战之后从头开始。在初步研究中，我们表明，来自这些动物的抗MPF4/肝素概括了命中免疫反应的关键方面，包括其可变发病率，血清学特异性和功能特性。我们还表明，动物中的MPF4/肝素抗体的产生需要CD4+ T-助血器细胞，并且在BALB/C和C57BL/6小鼠中，免疫召回率可变。使用这种动物模型，我们将：1）证明大分子PF4/肝素复合物的细胞活化。在此目标中，我们将进行体外和体内研究，以描绘对抗原的淋巴细胞反应，并证明MPF4/肝素复合物触发APC激活。 2）描述血小板激活和血小板CD154（CP40L）在诱导免疫反应诱导中的作用。我们的初步研究表明，体内血小板激活诱导PF4/肝素抗体产生。我们假设血小板激活对于HIT中的免疫起始至关重要，因为活化的血小板既提供了抗原（PF4）和共刺激信号（CD154）的来源。为了检验该假设，我们将研究血小板激活，MPF4和血小板CD154对命中免疫反应的敏感性作用。 3）描述了对PF4/肝素的鼠免疫反应中免疫调节机制受损的。我们的初步研究表明，BALB/C和C57BL/6小鼠的免疫召回模式的差异表明动物免疫调节功能的差异。在此目标中，我们将检验我们的假设，即调节性T细胞在定义HIT中免疫反应过程中起关键作用。预计这些研究将导致对预防或调节这种威胁生命的血栓性疾病的免疫并发症的策略的见解。