Studies on epithelial phagocytosis. II.―A method for demonstrating the origin of dust cells

Abstract

A method is described whereby the origin of alveolar phagocytes or dust-cells is demonstrated. Administration of benzol to rabbits reduces the blood leucocytes to negligible proportions; free and fixed cells of the reticulo-endothelial system are identified by injecting trypan blue; a suspension, such as hydro-kollog, is aseptically injected per tracheam. After introduction of the pigment, phagocytosis is shown, by microscopical examination of the lung, to be as active in benzol-treated animals as in intra-tracheally injected controls, thus eliminating the blood leucocytes as a source of dust-cells. Phagocytosis is quite as active in the lung3 of animals treated with benzol and trypan blue. Since dust-cells do not take a vital stain, their histiocytic origin can be eliminated. The only remaining sources are: (a) capillary endothelium of the lung (already discredited by this and previous papers) or (b) cells of the alveolar epithelium. The latter must then be definitely accepted as the origin of the dust-cells.