Inimmunology, themononuclear phagocyte system ormononuclear phagocytic system (MPS), also known as themacrophage system, is a part of theimmune system that consists of thephagocytic cells[1] located inreticular connective tissue. The cells are primarilymonocytes andmacrophages, and they accumulate inlymph nodes and thespleen. TheKupffer cells of theliver and tissuehistiocytes are also part of the MPS. The mononuclear phagocyte system and the monocyte macrophage system refer to two different entities, often mistakenly understood as one.[citation needed]
"Reticuloendothelial system" is an older term for the mononuclear phagocyte system, but it is used less commonly now, as it is understood that mostendothelial cells are notmacrophages.[2]
The mononuclear phagocyte system is also a somewhat dated concept trying to combine a broad range of cells, and should be used with caution.[3]
Thespleen is the second largest unit of the mononuclear phagocyte system. The monocyte is formed in the bone marrow and transported by the blood; it migrates into the tissues, where it transforms into a histiocyte or a macrophage.
Macrophages are diffusely scattered in the connective tissue and in liver (Kupffer cells), spleen and lymph nodes (sinus histiocytes), lungs (alveolar macrophages), and central nervous system (microglia). The half-life of blood monocytes is about 1 day, whereas the life span of tissue macrophages is several months or years. The mononuclear phagocyte system is part of both humoral and cell-mediated immunity. The mononuclear phagocyte system has an important role in defense against microorganisms, including mycobacteria, fungi, bacteria, protozoa, and viruses. Macrophages remove senescent erythrocytes, leukocytes, andmegakaryocytes byphagocytosis and digestion.
| Cell Name | Location |
|---|---|
| Adipose tissue macrophages | Adipose tissue |
| Monocyte | Bone Marrow/Blood |
| Kupffer cell | Liver |
| Sinus histiocytes | Lymph node |
| Alveolar macrophage (dust cell) | Pulmonary alveolus ofLungs |
| Tissue macrophages (Histiocyte) leading toGiant cells | Connective Tissues |
| Langerhans cell | Skin andMucosa |
| Microglia | Central Nervous System |
| Hofbauer cell | Placenta |
| Intraglomerular mesangial cell[4] | Kidney |
| Epithelioid histiocyte | Granulomas |
| Red Pulp Macrophage (Sinusoidal lining cells) | Red pulp ofSpleen |
| Peritoneal macrophages | Peritoneal cavity |
| Osteoclast | Bone |
The various cell types of the mononuclear phagocyte system are all part of themyeloid lineage from theCFU-GEMM (precursor of granulocytes, erythrocytes, monocytes and megakaryocytes).