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JAMA Revisited
August 2, 2016

The Protection of Micro-Organisms

JAMA. 2016;316(5):548. doi:10.1001/jama.2015.17096

“ ‘If ever there was a romantic chapter in pathology, it has surely been that of the story of phagocytosis.’ So said the late Lord Lister in his presidential address to the British Association in 1896, and so we, with equal fervor, say today when many more pages of the story have been turned over.”1 The term “phagocyte” was coined to designate the ameboid cells capable of seizing and digesting micro-organisms, red blood corpuscles and other formed structures. The property of phagocytosis is an attribute of a considerable number of different varieties of cells besides the more familiar representatives present in the circulating blood and tissue fluids. Zinsser2 states that among the fixed cells of the body it is probable that phagocytosis may be carried on by cells of many different origins, though the identification of cells in tissues is often a purely morphologic problem, and therefore fraught with many possibilities of error. Probably the most active fixed tissue cells are the endothelial cells of the blood vessels and those which line the serous cavities and the sinuses of the lymph nodes and of the spleen. In addition to these, however, there are many other cells which may be phagocytic. Zinsser and Carey have observed the active phagocytosis of leprosy bacilli by cells, probably of connective tissue origin, growing from plants of rat spleen in plasma. Phagocytosis by the cells lining the alveoli of the lungs has been observed by Briscoe. This author made the interesting observation that in cases of mild infection such cells can free the lungs of micro-organisms entirely without aid from the leukocytes of the circulating blood. It is these cells, too, which, in the ordinary conditions of life, take up the inhaled particles of dust and are often spoken of, therefore, as dust cells. These flattened cells are probably of epithelial origin, and as such are probably the only epithelial cells which act as phagocytes under ordinary conditions. Although no positive general statement is justified, we can yet say with reasonable accuracy that among the phagocytic fixed tissue cells the most important are the connective tissue and endothelial cells.

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