Platelets are covercytes, not phagocytes: Uptake of bacteria involves channels of the open canalicular system
Platelets are covercytes, not phagocytes: Uptake of bacteria involves channels of the open canalicular system
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DOI：
10.1080/09537100400007390
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发表时间：
2005-03-01
期刊：
影响因子：
3.3
通讯作者：
White, JG
中科院分区：
文献类型：
--
作者：
White, JG
最近的研究表明，人类血小板对细菌的摄取与中性粒细胞对相同生物体的摄取比之前认为的更为相似。血小板伪足通过圆周粘附过程包围细菌，直到生物体完全封闭在由质膜包围的内化细胞外空间组成的液泡中。表面相连的开放性小管系统（OCS）不参与血小板吞噬过程。本研究回顾了有关血小板-颗粒和血小板-细菌相互作用的文献，并添加了一项利用单宁酸作为电子致密示踪剂的细菌吞噬过程的新研究。固定过程中单宁和锇酸形成的锇黑反应产物将 OCS 的血小板外表面和内衬通道上的糖萼染色。它还对血小板中含有细菌的液泡以及连接到吞噬液泡和细胞外表面的 OCS 通道进行了染色。将其内容物释放到 OCS 和吞噬液泡中的阿尔法颗粒也被锇黑染色。在固定过程中，单宁酸能够到达并染色吞没液泡内表面的唯一途径是通过 OCS 的专利通道。相比之下，中性粒细胞不含有 OCS，并且含有生物体的吞噬液泡永远不会被单宁酸染色。因此，血小板是覆盖细胞，而不是吞噬细胞，细菌的摄取确实涉及 OCS 的通道。
Recent studies have suggested that uptake of bacteria by human platelets is more similar to ingestion of the same organisms by neutrophils than previously considered. Platelet pseudopods surround a bacterium by a process of circumferential adherence until the organism is fully enclosed in a vacuole consisting of internalized extracellular space surrounded by plasma membrane. The surface connected, open canalicular system (OCS) is not involved in the process of platelet phagocytosis. The present investigation has reviewed the literature on platelet-particle and platelet-bacterial interaction, and added a new study of the process of bacterial engulfment employing tannic acid as an electron dense tracer. The osmium black reaction product formed by tannic and osmic acids during fixation stained the glycocalyx on the platelet exterior surface and lining channels of the OCS. It also stained the vacuoles containing bacteria in platelets as well as channels of the OCS connected to the engulfment vacuole and exterior surface of the cell. Alpha granules releasing their contents into the OCS and into engulfment vacuoles were also stained by osmium black. The only way that tannic acid could reach and stain the interior surface of engulfment vacuoles during fixation was through patent channels of the OCS. In contrast, neutrophils do not contain an OCS, and phagocytic vacuoles containing organisms are never stained by tannic acid. Thus the platelet is a covercyte, not a phagocyte, and uptake of the bacteria does involve channels of the OCS.