Biochemical Aspects of the Function of the Reticulo-Endothelial System

Abstract

The title of this presentation was assigned, and it is truly doubtful whether we can present a picture that is consistent with the assignment. The reasons for this are manifold. First, the reticulo-endothelial system per se, as it was defined by Aschoff (1) is a broader group of cells than we are competent to discuss. Indeed, we find ourselves much more comfortable with the concept of the “mononuclear phagocyte system” proposed at the conference on Mononuclear Phagocytes in Leiden, 1969 (18). The system, as described there, is concerned with mononuclear phagocytes, a group of cells that are related in morphology, functions and origin, ranging from the promonocytes through the monocytes of the blood to the macrophages of the tissues, including histiocytes, Kupffer cells, the alveolar macrophages; macrophages of the spleen, lymph nodes, bone marrow, peritoneum and bone tissue; and the microglia of the nervous system. Obviously there is overlap between the two classifications. What we shall have to say in this report will focus largely on the macrophage as it is obtained by simple lavage from the peritoneal cavity; from the peritoneal cavity after elicitation with an agent such as caseinate; or as it is washed out of the alveoli. It is not that biochemical studies have not been performed on other cells of this system--there have been such studies, e.g., on the Kupffer cells of the liver, but these studies are relatively few and perhaps more difficult to interpret than experiments on defined cell populations.