Effect of Neutrophil Priming on Chemotaxis and Signaling

描述（由申请人提供）： 多形性白细胞（PMN）是一种固有的运动细胞类型，可以被引导向上移动的化学引诱物梯度。趋化运动是必不可少的PMN积累在组织损伤或感染的网站，然而，提供导航信号需要给这些细胞的方向的机制是不完全了解。白色念珠菌是医院感染的第四大原因，术后、创伤和免疫抑制患者的感染风险最高。β-葡聚糖是酵母细胞壁的一种主要成分，在全身性念珠菌病患者的血液中被加工，尽管β-葡聚糖在疾病的病理生物学中的作用尚不清楚。该实验室最近的研究结果表明，β-葡聚糖将PMN迁移从随机迁移转化为直接迁移。这种转化是通过白细胞β 2整合素CR 3（CD 11 B/CD 18）识别β-葡聚糖介导的，是以前未认识到的β-葡聚糖对中性粒细胞功能的影响。我们工作的长期目标是了解在系统性真菌感染过程中β-葡聚糖如何影响宿主防御。目前建议的重点是确定CR 3识别β-葡聚糖改变中性粒细胞功能的机制。目标I中的实验将研究几种细胞内信号传导途径的作用，根据我们目前的发现，假设这些信号传导途径介导中性粒细胞在β-葡聚糖补充基质上迁移的趋化能力增加。具体目标II将应用一个充分表征的伤口模型来证明β-葡聚糖对宿主中性粒细胞对损伤作出反应的能力的影响。体外研究结果表明，β-葡聚糖激活CR 3可调节β 1家族整合素的功能。伤口模型将确定β-葡聚糖和/或系统性念珠菌病是否类似地改变β 1整联蛋白介导PMN进入损伤部位的功能。最后，几种促炎介质（LPS、免疫复合物、尿激酶纤溶酶原激活剂）结合糖基磷脂酰肌醇（GPI）连接的受体（CD 14、CD 16、CD 87），其转而依赖于CR 3进行细胞内信号传导。具体目标III将测试β 1整联蛋白串扰的新途径使GP 1连接的受体与CR 3分子解离的假设。由于β-葡聚糖和GPl连接的受体共享共同的CR 3结合位点，因此GPl连接的受体与CR 3的解离将同时增加可用于β-葡聚糖结合的CR 3分子的数量并减弱对GPl连接的受体特异性配体的应答。拟议的研究将进一步阐明β-葡聚糖引发中性粒细胞的作用机制，作为系统性真菌感染的一种成分，并作为具有治疗多微生物败血症的治疗潜力的生物反应调节剂。

DESCRIPTION (provided by applicant): Polymorphonuclear leukocytes (PMN) are an inherently motile cell type, which can be directed to move up a chemoattractant gradient. Chemotactic movement is essential for PMN accumulation at sites of tissue injury or infection, however, mechanisms which provide the navigational signals needed to give direction to these cells are incompletely understood. Candida albicans is the fourth leading cause of nosocomial infections with post-surgical, trauma and immunosuppressed patients being at highest risk. Beta-glucan, a major component of the yeast cell wall, is elaborated into the bloodstream of patients with systemic candidiasis although the role of beta-glucan in the pathobiology of the disease is not clear. Recent findings from this laboratory have shown beta-glucan, converts PMN migration from random to direct. The conversion is mediated by recognition of beta-glucan by the leukocyte beta2integrin CR3 (CD11 b/CD18) and is a previously unrecognized effect of beta-glucan on neutrophil function. The long-term goal of our work is to understand how host defenses are affected by beta-glucan during the course of systemic fungal infections. The focus of the current proposal is to determine the mechanisms through which beta-glucan recognition by CR3 alters neutrophil function. Experiments in Aim I will investigate the role of several intracellular signaling pathways that, based on our current findings, are hypothesized to mediate the increased chemotactic capacity of neutrophils migrating on beta-glucan supplemented matrix. Specific Aim II will apply a well-characterized wound model to demonstrate the effect of beta-glucan on the ability of the host neutrophils to respond to injury. In vitro findings have determined that activation of CR3 by beta-glucan regulates the function of integrins of the beta1 family. The wound model will determine whether beta-glucan and/or systemic candidiasis similarly alters the function of beta1 integrins in mediating PMN entry into a site of injury. Finally, several proinflammatory mediators (LPS, immune complexes, urokinase plasminogen activator) bind to glycosylphosphatidylinositol (GPI)-Iinked receptors (CD14, CD16, CD87), which in turn rely on CR3 for intracellular signaling. Specific Aim III will test the hypothesis that a novel pathway of beta1 integrin crosstalk dissociates GPl-linked receptors from CR3 molecules. Since beta-glucan and GPl-linked receptors share a common CR3 binding site, dissociation of GPl-linked receptor from CR3 would simultaneously increase the number of CR3 molecules available for beta-glucan binding and blunt the response to ligands specific for GPl-linked receptors. The proposed studies will further elucidate the mechanism of action through which beta-glucan primes neutrophils both as a component of systemic fungal infections and as a biological response modifier with therapeutic potential for treating polymicrobial sepsis.