Reticuloendothelial System RES

a system of cells of mesenchymal origin in vertebrate animals and in man that can be converted to actively mobile phagocytic cells (macrophages). I.I. Mechnikov, who originated the theory of the reticuloendothelial system, demonstrated in his studies on inflammation that some connective-tissue and blood cells can be converted to macrophages. The cells of the RES include connective-tissue histiocytes, monocytes of the blood, reticular cells, endothelial cells of the capillaries, cells of hematopoietic and other organs (for example, the adrenal glands), and Kupffer’s cells.

In addition to the RES’s protective function and involvement in the immunological processes, the system apparently takes part in neutralizing the harmful effects of a number of metabolites, in intermediate protein and fat metabolism, and in pigment metabolism. The destruction and utilization of old erythrocytes and the formation of bile pigments occur in RES cells, mainly in those of the spleen and liver. The accumulation of pigment particles in the RES cells changes the color of organs to rust brown or black. The accumulation of lipids cause substantial enlargement of organs, especially those with a developed RES, for example, the spleen and liver.

The part played by the RES in tumor development has been demonstrated experimentally. Removal of organs rich in reticuloendothelial cells, such as the spleen, lowers resistance in animals, thus promoting the development of a grafted tumor’s foreign tissue. Hyperplastic developments in the RES sometimes lead to the formation of tumors (reticuloendotheliosis) and affect the entire system. Reticulosarcoma is one such development.

The research of such Soviet scientists as N. N. Anichkov and A. A. Bogomolets has contributed greatly to our knowledge of the reticuloendothelial system.