发布: 2018年09月20日第8卷第18期 DOI: 10.21769/BioProtoc.3018 浏览次数: 6170
评审: Andrea PuharSuprabhat MukherjeeLip Nam LOH
Abstract
Blood platelets are critical for hemostasis and thrombosis, but also play diverse roles during immune responses. We have recently reported that platelets migrate at sites of infection in vitro and in vivo. Importantly, platelets use their ability to migrate to collect and bundle fibrin (ogen)-bound bacteria accomplishing efficient intravascular bacterial trapping. Here, we describe a method that allows analyzing platelet migration in vitro, focusing on their ability to collect bacteria and trap bacteria under flow.
Keywords: Platelets (血小板)Background
Platelets are small, anucleate cellular fragments released from megakaryocytes that reside within the bone marrow of mammalian organisms (Machlus and Italiano, 2013). Approximately 750 billion platelets circulate in human blood, constantly scanning the vasculature for damage of the endothelial surface. Upon encountering endothelial injury, platelets are immediately recruited in a well-characterized cascade of events including initial platelet tethering and rolling, followed by platelet activation, adhesion and spreading, eventually leading to fibrin (ogen)-dependent aggregation and subsequent thrombus retraction (Jackson, 2007). Platelet plug formation is a major step in physiological hemostasis, but also in pathological thrombosis after atherosclerotic plaque rupture, triggering myocardial infarction or stroke (Jackson, 2011).
In addition to their well-established role in hemostasis and thrombosis, platelets also evolved diverse immunologic functions (Semple et al., 2011). Being among the first cells recruited to sites of inflammation and infection, platelets play an essential role in initiating intravascular immune responses (Wong et al., 2013). Accordingly, platelets coordinate the recruitment of a variety of immune cells and instruct them with their effector programs (Sreeramkumar et al., 2014). Platelets also have the ability to directly fight pathogens by releasing anti-microbial mediators and/or physically trapping and encapsulating invaders, thus preventing dissemination with the blood flow (Yeaman, 2014).
We recently identified platelet migration as an autonomous platelet function and showed that migration of single platelets provides a mechanism of controlling their interaction with pathogenic bacteria within the microcirculation (Gaertner et al., 2017). Once adhering to immobilized fibrin (ogen), activated platelets use αIIbβ3 integrins to probe the resistance of their local microenvironment. When actomyosin-dependent traction forces overcome substrate resistance platelets eventually polarize and migrate thereby removing and accumulating platelet-bound ligands. As a prominent example, migrating platelets collect and bundle fibrin (ogen)-bound bacteria accomplishing efficient intravascular bacterial trapping. In contrast to phagocytes like neutrophils, platelets behave like “covercytes” that do not internalize collected bacteria but rather accumulate them on their surface within invaginations of the plasma membrane (White, 2005). When exposed to shear stress in vitro platelets strongly bind to piled-up bacteria.
Here we provide a detailed protocol for the isolation of platelets from human blood and microscopic observation of platelet migration and trapping of Escherichia coli (E. coli) under flow.
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文章信息
版权信息
© 2018 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
Fan, S., Lorenz, M., Massberg, S. and Gaertner, F. (2018). Platelet Migration and Bacterial Trapping Assay under Flow. Bio-protocol 8(18): e3018. DOI: 10.21769/BioProtoc.3018.
分类
免疫学 > 宿主防御 > 人
微生物学 > 微生物-宿主相互作用 > 细菌
细胞生物学 > 细胞分离和培养 > 细胞分离
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