Reticuloendothelial

Reticuloendothelial, in its historical usage, refers to the reticuloendothelial system (RES), a network of phagocytic cells that line the circulatory and lymphatic systems and inhabit various tissues. The term has been used to describe macrophages and related cells capable of endocytosis and antigen processing.

Key components include tissue-resident macrophages such as Kupffer cells in the liver, splenic macrophages, alveolar macrophages in the lungs, and microglia in the brain, as well as dendritic cells and circulating monocytes. These cells form a dispersed, interconnected system across organs including the liver, spleen, lymph nodes, bone marrow, and lungs.

Functions include phagocytosis of bacteria, dead cells, and debris; clearance of immune complexes; recycling of iron from senescent erythrocytes; antigen processing and presentation to lymphocytes; cytokine production; and roles in tissue remodeling and lipid metabolism.

Modern immunology often replaces the term reticuloendothelial system with the mononuclear phagocyte system (MPS), which more precisely describes the lineage and diversity of macrophages, monocytes, and dendritic cells. The RES concept remains useful historically and in some clinical contexts, but the term RES can be misleading because it excludes nonphagocytic or migratory cells that participate in immune surveillance.

Clinical relevance: alterations in RES activity are observed in infections, anemia of inflammation, storage diseases, and splenic dysfunction. Splenectomy or asplenia can reduce RES clearance and alter iron recycling and immune surveillance.