Gehr P, Im Hof V, Geiser M, Schürch S
Abteilung für Histologie, Universität Bern.
Schweiz Med Wochenschr. 2000 May 13;130(19):691-8.
Many pollution particles enter the organism via the lung. In the lung, on a surface of 140 m2, the blood is separated from the air by a tissue barrier of only 1/1000 mm. The conducting airways (trachea, bronchi, bronchioli) are a very effective aerodynamic filter for inhaled particles. The mucociliary transport system functions like a self-cleaning mechanism within the filter. Inhaled particles and particles deposited in the lungs play a crucial aetiological and therapeutic role. The discussion in health policy on the relationship between the increase in air pollution and lung damage is of great importance at the present time. Epidemiological studies of recent years have shown very clearly that there is a correlation between morbidity and mortality as a consequence of respiratory and cardiogenic problems and the concentration of PM10 particles in ambient air. So far, however, this correlation has not been explained. The intrathoracic airways are coated by a respiratory epithelium. This has an irregular coating of viscous liquid, consisting of a low viscous sol phase and a high viscous gel phase. It seems, however, that those phases are not clearly distinguishable. The gel phase is moved towards the pharynx by the metachronal ciliary beat transporting the particles out of the lungs. Furthermore, at the air-liquid interface, there exists a continuous surfactant film which reduces the surface tension as is the case in the alveoli. When particles are deposited on the airway wall, that is, on the surfactant film, they are wetted by surface forces and displaced into the liquid phases. Thus, the surfaces of the particles are probably changed by the surfactant or by surfactant components. Many of these particles are transported in the liquid (gel phase) towards the pharynx (mucociliary transport), whereas some of them remain in close association with the epithelium (sol phase). Such particles remain in the airways for days or even weeks. They are either phagocytised by macrophages and carried off via the airways or taken up by dendritic cells and transported into the tissue from where they reach the lymph nodes via lymph drainage and are presented to the T-lymphocytes. The displacement of particles into the liquid phases, caused by the surfactant, can be considered as the initial step in a complex cascade of defence processes in the lungs. The surface of the particles is probably modified by surfactant or surfactant components. These modified particles may be directed to that clearance pathway which is most beneficial for our health, that is, out of the lungs or into the lymphatic glands, where an immune reaction can be triggered. We therefore consider surfactant to be a primary immune barrier.
许多污染颗粒通过肺部进入机体。在肺部，140平方米的表面积上，血液与空气仅被一层厚度为千分之一毫米的组织屏障分隔开来。传导气道（气管、支气管、细支气管）对吸入颗粒而言是一种非常有效的空气动力学过滤器。黏液纤毛运输系统在该过滤器中起着自我清洁机制的作用。吸入的颗粒以及沉积在肺部的颗粒起着至关重要的病因学和治疗学作用。当前，卫生政策中关于空气污染增加与肺部损害之间关系的讨论极为重要。近年来的流行病学研究已非常清楚地表明，由呼吸和心源性问题导致的发病率和死亡率与环境空气中PM10颗粒的浓度之间存在相关性。然而，到目前为止，这种相关性尚未得到解释。胸腔内气道由呼吸上皮覆盖。其表面有一层不规则的黏性液体涂层，由低黏性溶胶相和高黏性凝胶相组成。然而，似乎这两个相并不容易区分。凝胶相通过同步纤毛摆动朝着咽部移动，从而将颗粒带出肺部。此外，在气液界面存在一层连续的表面活性剂膜，它能降低表面张力，这与肺泡中的情况相同。当颗粒沉积在气道壁上，也就是表面活性剂膜上时，它们会因表面力而被湿润并移入液相。因此，颗粒的表面可能会被表面活性剂或表面活性剂成分改变。许多此类颗粒会在液体（凝胶相）中朝着咽部运输（黏液纤毛运输），而其中一些会与上皮紧密结合（溶胶相）。这些颗粒会在气道中停留数天甚至数周。它们要么被巨噬细胞吞噬并通过气道排出，要么被树突状细胞摄取并转运到组织中，然后通过淋巴引流到达淋巴结并呈递给T淋巴细胞。由表面活性剂导致的颗粒移入液相可被视为肺部复杂防御过程级联反应的初始步骤。颗粒的表面可能会被表面活性剂或表面活性剂成分修饰。这些修饰后的颗粒可能会被导向对我们健康最有益的清除途径，即排出肺部或进入淋巴结腺，在那里可以引发免疫反应。因此，我们认为表面活性剂是一道主要的免疫屏障。
