Editing Mononuclear phagocyte system

{{Short description|Part of the immune system}}
{{distinguish|reticulocyte|reticular cell|reticuloendothelial system}}

In [[immunology]], the '''mononuclear phagocyte system''' or '''mononuclear phagocytic system''' ('''MPS'''), also known as the '''macrophage system''', is a part of the [[immune system]] that consists of the [[Phagocyte|phagocytic cells]]<ref>{{MeshName|Mononuclear+Phagocyte+System}}</ref> located in [[reticular connective tissue]]. The cells are primarily [[monocyte]]s and [[macrophage]]s, and they accumulate in [[lymph node]]s and the [[spleen]]. The [[Kupffer cell]]s of the [[liver]] and tissue [[histiocyte]]s 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|reason=Reliable source needed for the whole sentence|date=April 2020}}

"[[Reticuloendothelial system]]" is an older term for the mononuclear phagocyte system, but it is used less commonly now, as it is understood that most [[endothelial]] cells are not [[macrophage]]s.<ref name="Singh2006">{{cite book|author=Inderbir Singh|title=Textbook of human histology|url=https://books.google.com/books?id=Ej22iANgNkoC&pg=PA90|access-date=12 November 2010|year=2006|publisher=Jaypee Brothers Publishers|isbn=978-81-8061-809-3|pages=90–}}{{Dead link|date=August 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

The mononuclear phagocyte system is also a somewhat dated concept trying to combine a broad range of cells, and should be used with caution.<ref>{{Cite journal|last=Hume|first=David A|date=2006-02-01|title=The mononuclear phagocyte system|journal=Current Opinion in Immunology|series=Innate immunity / Antigen processing and recognition|volume=18|issue=1|pages=49–53|doi=10.1016/j.coi.2005.11.008|pmid=16338128}}</ref>

==Cell types and locations==

The [[spleen]] 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, and [[megakaryocyte]]s by [[phagocytosis]] and digestion.

{| class="wikitable",
! Cell Name || Location
|-
| [[Adipose tissue macrophages]] || [[Adipose tissue]]
|-
| [[Monocyte]] || [[Bone Marrow]]/[[Blood]]
|-
| [[Kupffer cell]] || [[Liver]]
|-
| [[Medulla of lymph node|Sinus histiocytes]] || [[Lymph node]]
|-
| [[Alveolar macrophage]] (dust cell) || [[Pulmonary alveolus]] of [[Lungs]]
|-
| [[Macrophage#Tissue macrophages|Tissue macrophages]] (Histiocyte) leading to [[Giant cell]]s || [[Connective Tissues]]
|-
| [[Langerhans cell]] || [[Skin]] and [[Mucosa]]
|-
| [[Microglia]] || [[Central Nervous System]]
|-
| [[Hofbauer cell]]  || [[Placenta]]
|-
| [[Intraglomerular mesangial cell]]<ref>{{cite book |last=Lote |first=Christopher J. |title= Principles of Renal Physiology, 5th edition|publisher=Springer |page=37}}</ref> || [[Kidney]]
|-
| [[Epithelioid cell|Epithelioid]] histiocyte  || [[Granulomas]]
|-
| [[Red pulp|Red Pulp Macrophage]] ([[Sinusoid (blood vessel)|Sinusoidal]] lining cells) || Red pulp of [[Spleen]]
|-
| Peritoneal macrophages   || [[Peritoneal cavity]]
|-
| [[Osteoclast]]  || [[Bone]]
|-
|}

==Functions==
* Formation of new red blood cells (RBCs) and white blood cells (WBCs).
* Destruction of senescent RBCs.
* Formation of plasma proteins.
* Formation of bile pigments.
* Storage of iron. In the liver, Kupffer cells store excess iron from [[catabolism]] of [[heme]] from the breakdown of red blood cells. In bone marrow and spleen, iron is stored in MPS cells mostly as [[ferritin]]; in iron overload states, most of the iron is stored as [[hemosiderin]].
* Clearance of [[heparin]] via heparinases.

==Hematopoiesis==
The various cell types of the mononuclear phagocyte system are all part of the [[myeloid]] lineage from the [[CFU-GEMM]] (precursor of granulocytes, erythrocytes, monocytes and megakaryocytes).

==References==

{{reflist}}
==External links==
* {{GeorgiaImmunology|1/reticulo}}

{{Myeloid blood cells and plasma}}
{{Authority control}}
[[Category:Immune system]]