A 3-D perspective on neutrophil migration

趋化性是细胞可以向化学引诱物的来源导航的过程。它对发育，免疫功能和癌细胞的扩散至关重要。它基于细胞通过其表面上的高度特异性受体检测化学引诱物的能力。值得注意的是，当放置在趋化剂来源附近时，细胞可以确定朝向其来源的方向。它利用引诱剂在靠近源的地方变得更集中的事实和它检测周围化学引诱剂浓度的微小差异的能力来实现这一点，然后细胞朝着化学引诱剂浓度增加的方向迁移。尽管它的重要性，我们的了解如何趋化性工程是非常有限的。很明显，趋化性是由许多组分或子反应组成的。检测趋化因子的能力，在非常小的距离内感知其浓度变化的能力，以及响应于趋化因子而移动的能力（化学运动），这又取决于细胞与相邻细胞或表面形成可逆接触的能力。对趋化性的全面理解只能从对这些元素成分反应的理解中产生。在这个项目中，我们专注于化学运动（化学引诱物刺激的运动，在我们的测定中，化学引诱物的浓度通常是均匀的，所产生的迁移是随机的，而不是像趋化性那样定向的）作为趋化性中的关键事件的机制。我们的目标是了解化学性质（作为信号的分子）和细胞内过程的空间组织，使它们能够执行这些反应。中性粒细胞是血液中发现的一种特殊形式的白色细胞。它们的主要功能是摄取和杀死细菌和真菌病原体。中性粒细胞利用趋化性过程从血流中迁移到炎症区域，并归巢病原体。因此，趋化性对于中性粒细胞执行其正常健康功能对抗疾病是必不可少的。然而，已知许多长期炎性疾病是由中性粒细胞过度反应引起的。太多的中性粒细胞在疾病部位积聚，实际上有助于宿主组织损伤，这反过来又导致中性粒细胞的进一步积聚。因此，治疗炎性疾病如关节炎的主要目的是减少中性粒细胞向炎症部位的迁移。目前，我们很少有药物能够有效地减少中性粒细胞流入慢性炎症部位，并产生不必要的副作用，因为我们不知道趋化性中的哪些步骤是最佳靶点。我们的目的是研究中性粒细胞的趋化作用和趋化性。最近，在了解中性粒细胞内参与协调趋化性的事件方面取得了巨大进展。这是可能的，通过显微镜的发展，能够看到内部活的中性粒细胞，因为他们移动和使用基因工程技术，使特定的蛋白质，我们想研究细胞内的荧光，因此可以看到特殊的照明和检测系统在显微镜。然而，尽管有这些进步，我们在趋化过程中对细胞内部的观察到目前为止还是非常二维的，就好像我们从上面向下看它们一样，不能揭示任何深度（细胞的“侧面”）。通过使用新的成像技术，我们能够开始拍摄许多照片，并将它们联合收割机组合起来，给人一种深度感。到目前为止，我们所看到的完全改变了我们对二维图像的解释和对趋化性空间协调的理解。在这个项目中，我们希望利用数学和计算机来提高我们创建和重建迁移中性粒细胞的3D图像的能力，并利用它来找出调节趋化作用和趋化性的细胞内信号的本质。

Chemotaxis is the process by which cells can navigate towards sources of chemoattractant. It is crucial for development, immune function and the spread of cancer cells. It is based on the ability of cells to detect chemoattractants via highly specific receptors on their surface. Remarkably, when placed near to a source of chemottractant the cell can determine the direction towards its source. It achieves this by using both the fact that the attractant becomes more concentrated nearer the source and its ability to detect tiny differences in the concentration of chemoattractant around it. The cell then migrates in the direction of increasing concentration of chemottractant. Despite its importance our understanding of how chemotaxis works is very limited. It is clear that chemotaxis is made up of many component, or sub, responses. The ability to detect the chemottractant, the ability to sense changes in its concentration across very small distances and the ability to move in response to the chemoattractant (chemokinesis), which is in turn dependent on the ability of the cells to form reversible contacts with neighbouring cells or surfaces. A full understanding of chemotaxis will only emerge from an understanding of these elemental component responses. In this project we focus on the mechanisms underpinning chemokinesis (chemoattractant stimulated movement, in our assays the chemottractants are often uniform in concentration and the resulting migration is random and not directed as in chemotaxis) as a key event in chemotaxis. We aim to understand the chemical nature (the molecules that are acting as the signals) and spatial organisation of the processes inside cells that allow them to perform these responses. Neutrophils are a specialised form of white cell found in the blood. Their primary function is to ingest and kill bacterial and fungal pathogens. Neutrophils use the process of chemotaxis to migrate out of the blood stream towards areas of inflammation and also to home-in on pathogens. Thus chemotaxis is essential for neutrophils to perform their normal healthy function fighting disease. However, many long term inflammatory diseases are known to caused by neutrophils over-reacting. Too many neutrophils accumulate at the site of disease and actually contribute to host tissue damage, which in-turn leads to further accumulation of neutrophils. Hence a major objective in treating inflammatory disease such as arthritis is to reduce neutrophil migration into sites of inflammation. At the moment we have very few drugs that are able to effectively reduce neutrophil influx to sites of chronic inflammation with unwanted side effects because we do not know which steps in chemotaxis to best target. We aim to study neutrophil chemokinesis and chemotaxis. Recently there has been huge progress in understanding the events inside neutrophils that are involved in coordinating chemotaxis. This has been possible through the development of microscopes capable of seeing inside living neutrophils as they move and the use of genetic engineering techniques to make specific proteins we want to study inside cells fluorescent and hence possible to see with special illumination and detection systems in the microscopes. However, despite these advances our views of the inside of cells during chemotaxis has thus far been very 2-dimensional, that is as if we were looking down on them from above, and could not reveal any depth (the 'sides' of the cell). By using new imaging techniques we are able to begin to take many photos and combine them to give a sense of depth. What we have seen so far entirely changes our interpretation of the 2-D images and understanding of the spatial coordination of chemotaxis. In this project we hope to use mathematics and computers to improve our ability to create and interprete 3-D images of migrating neutrophils and to use this to find out the nature of the intracellular signals that regulate chemokinesis and chemotaxis.