Institute of Anatomy, University of Bern, Bern, Switzerland.
J Aerosol Med Pulm Drug Deliv. 2010 Aug;23(4):207-17. doi: 10.1089/jamp.2009.0797.
Lung macrophages, that is, the intravascular, interstitial, pleural, and surface macrophages, are part of the mononuclear phagocyte system. They are derived from the hematopoietic stem cell in the bone marrow with the monocytes as their putative precursors. Macrophages residing on the inner surfaces of the lungs and immersed within the lung lining layer, that is, the alveolar and the airway macrophages, are constantly exposed to the environment; it is those cells that are recognized as first line of cellular host defense.
Phagocytic uptake of inhaled and deposited particles is the main mechanism to remove insoluble micrometer-sized particles from the lung surfaces, where mucociliary transport, cough, or sneezing fail or are absent. Phagocytosis requires an intact cytoskeleton and is most efficient when mediated by Fc-receptors, but complement and scavenger receptors like MARCO and CD206 are just as important. The main pathway for the clearance of macrophage-associated particles is by mucociliary transport; to a lesser degree and species specific, particle-containing macrophages may reenter into the interstitium and go from there to the lymphatics. Inhaled nanometer-sized particles that deposit along the entire respiratory tract, however, are not efficiently phagocytosed by surface macrophages.
Uptake by spontaneous or stimulated (macro-) pinocytosis or electrokinetic's phenomena may become more important. In addition, translocation of nanometer-sized particles into the interstitium and to the blood circulation brings them into contact with other fluids; altered particle properties may influence particle uptake. Moreover, translocated particles may interact with lung macrophage populations that were previously not considered of great significance for the clearance of inhaled particles.
肺巨噬细胞，即血管内、间质、胸膜和表面巨噬细胞，是单核吞噬细胞系统的一部分。它们来源于骨髓中的造血干细胞，单核细胞是其潜在前体。驻留在肺内表面并沉浸在肺衬里层中的巨噬细胞，即肺泡和气道巨噬细胞，不断暴露于环境中；正是这些细胞被认为是细胞宿主防御的第一道防线。
吞噬作用是从肺表面清除不可溶性微米大小颗粒的主要机制，在那里，黏液纤毛转运、咳嗽或打喷嚏失败或不存在。吞噬作用需要完整的细胞骨架，并且当由 Fc 受体介导时效率最高，但补体和清道夫受体（如 MARCO 和 CD206）同样重要。清除与巨噬细胞相关的颗粒的主要途径是通过黏液纤毛转运；在较小程度上和物种特异性上，含颗粒的巨噬细胞可能重新进入间质，并从那里进入淋巴管。然而，沿整个呼吸道沉积的纳米大小的颗粒不能被表面巨噬细胞有效吞噬。
自发或刺激（大）胞饮作用或电动现象的摄取可能变得更为重要。此外，纳米大小的颗粒向间质和血液循环中的转移使它们与其他液体接触；改变颗粒的性质可能会影响颗粒的摄取。此外，转移的颗粒可能与以前被认为对吸入颗粒清除作用不重要的肺巨噬细胞群体相互作用。
