Mononuclear phagocyte system
The mononuclear phagocyte system is a system comprised of phagocytic cells located in reticular connective tissue. Reticular connective tissue is a type of connective tissue characterized by the predominance of reticular fibers, such as those found in spleen, lymph nodes, and bone marrow. The mononuclear phagocyte system is formerly referred to as reticuloendothelial system. The latter is no longer common for use since most endothelial cells are not macrophages.1
The mononuclear phagocytic system is part of the immune system. It consists of the phagocytic cells that are primarily involved in phagocytosis and antigen processing and presentation. Thus, the system is a part of both humoral and cell-mediated immunity. Apart from immune functions, the system is also involved in the formation of plasma proteins, new erythrocytes and leukocytes, and bile pigments, the storage of excess iron (e.g. as ferritin and as hemosiderin), the removal of old RBCs and WBCs by phagocytosis, and the clearance of heparin with the help of the enzyme heparinase.2
Examples of cells of mononuclear phagocyte system are as follows: 2 (1) adipose tissue macrophages in adipose tissues, (2) monocytes in bone marrow, (3) Kupffer cells in liver, (3) sinus histiocytes in lymph nodes, (4) alveolar macrophage in pulmonary alveolus of lungs, (5) histiocytes in connective tissues, (6) Langerhans cells in skin and mucosa, (7) microglia in central nervous system, (8) Hofbauer cells in placenta, (9) intraglomerular mesangial cells in kidneys, (10) osteoclasts in bone, (11) epithelioid cells in granulomas, (12) red pulp macrophages in the red pulp of spleen, and peritoneal macrophages in the peritoneal cavity.
- reticuloendothelial system
1 Singh, I. (2006). Textbook of Human Histology. Jaypee Brothers Publishers. pp. 90–.
2 Mononuclear phagocyte system. Retrieved from .