Re-evaluation of the reticulo-endothelial system

By injecting lithium carmine (Lit-car) into living animals, Ribbert (1904) and Kiyono (1914) showed that specific staining occurred in some cells in v arious organs. Kiyono termed those cells "histiocytes" which consisted of f ree amoeboid cells and cells of reticulo-endothelium. Aschoff (1924) introd uced the concept 'reticulo-endothelial system (RES) for the collection of c ells having in common the property of vital staining. Van Furth (1972) prop osed the term "mononuclear phagocyte system (MPS)" advocated that RES be re placed by MPS. As a consequence we presently suffer from a "reticulo-endoth elial confusion", based on the delusion that cells other than macrophages; are not members of the RES. The point that most clearly illustrates this is the fact that the Lit-car-laden cells in the body are named macrophages in modem textbooks of histology. To clarify the confusion, we re-examined the vital staining at light and el ectron microscopic levels and analyzed the scavenger cells using biochemica l methods. Injected Lit-car was actively endocytosed by sinusoidal endothel ial cells in the liver and reticular cells in the sinus of lymph nodes. Of note, uptake of the dye was comparatively much lower in macrophages/monocyt es. Our findings indicate the existence of scavenger endothelial cells and reticular cells in blood and lymphatic circulations respectively. We name t hese two systems "the scavenger RES" collectively.