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Reticuloendothelial system

 
Sci-Tech Dictionary: reticuloendothelial system
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(rə¦tik·yə·lō′en·dō′thē·lē·əl ′sis·təm)

(anatomy) The macrophage system, including all phagocytic cells such as histiocytes, macrophages, reticular cells, monocytes, and microglia, except the granular white blood cells. Abbreviated RES. Also known as hematopoietic system; reticular system.

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Britannica Concise Encyclopedia: reticuloendothelial system
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Part of the body's defenses, consisting of a class of cells widely distributed in the body. Reticuloendothelial cells filter out and destroy bacteria, viruses, and foreign substances and destroy worn-out or abnormal cells and tissues. Precursor cells in bone marrow develop into monocytes (see leukocyte), which are released into the bloodstream. Most enter body tissues, developing into much larger cells called macrophages, with different appearances in various locations. Some roam through the circulation and between cells and can coalesce into a single cell around a foreign object to engulf it. Reticuloendothelial cells also interact with lymphocytes in immune reactions. Cells in the spleen destroy old red blood cells and recycle their hemoglobin; uncontrolled, this process causes anemia. Tumours of the reticuloendothelial system can be localized or widespread throughout the body. See also lymphatic system.

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Veterinary Dictionary: reticuloendothelial system
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A term that encompasses the monocyte–macrophage or mononuclear phagocytic system and also includes reticulum cells. It consists of a population of cells called macrophages, which are of bone marrow origin and are widely distributed throughout the body. Immature macrophages or monocytes make up about 5% of peripheral blood leukocytes. Mature macrophages are found in connective tissue (histiocytes), lining hepatic sinusoids (Kupffer cells), in the lung (alveolar macrophages), brain (microglia) and skin (Langerhans cells). They are also found in the spleen, lymph nodes and bone marrow. The major roles of these cells include: phagocytosis, antigen-processing and trapping, regulation of immune responses and the secretion of several biologically important factors such as interleukin 1, lysozyme, plasminogen activator and complement components.
The macrophages of the spleen possess the ability to dispose of disintegrated erythrocytes. They do not, however, destroy hemoglobin, which is liberated in the process.
Kupffer cells, together with the cells of the general connective tissue and bone marrow, are capable of transforming into bile pigment the hemoglobin released by disintegrated erythrocytes.

Wikipedia: Reticuloendothelial system
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The reticuloendothelial system (RES), part of the immune system, consists of the phagocytic cells located in reticular connective tissue, primarily monocytes and macrophages. These cells accumulate in lymph nodes and the spleen. The Kupffer cells of the liver and tissue histiocytes are also part of the RES.

Mononuclear phagocytic system and lymphoreticular system are synonymous with RES.

The reticuloendothelial system is divided into primary and secondary lymphoid organs.

Contents

Primary lymphoid organs

Primary (or "central") lymphoid organs - the sites where the cells of the RES are produced. The cells of the RES are produced in the bone marrow.

The thymus is also included as it is the required site for T cell maturation.

Secondary lymphoid organs

Secondary (or "peripheral") lymphoid organs - the sites where the cells of the RES function. This includes the lymph nodes, tonsils, spleen, and "MALT" (mucosa-associated lymphoid tissue).

  • The Kupffer cells of the liver act as part of this system but are not organized into a tissue; rather, they are dispersed throughout the liver sinusoids.
  • The microglia of the Central Nervous System (CNS) can be considered a part of the reticuloendoethelial system. They are scavenger cells that proliferate in response to CNS injury.

Function

The secondary lymphoid structures function to survey all entering or circulating antigen and to mobilize an immune response against foreign antigen upon its discovery. The GALT and BALT are exposed to antigens entering the gastrointestinal and respiratory tracts, respectively. All extracellular fluid must filter through lymph nodes as it traverses the lymphatics on its way back to the systemic circulation. Antigen residing in the interstitium is thus swept to the lymph nodes for processing.

Finally, the spleen filters the blood in search of antigen. Upon the discovery of foreign antigen, all of these tissues react in a similar manner to amass an appropriate and multifaceted immune response.

Clinical significance

Lymphoma of the reticuloendothelial system is called reticuloendotheliosis.

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Immune system / Immunology
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Antigens
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Immune cells/
White blood cells
Lymphoid: T cell · B cell · NK cell

Myeloid: Mast cell · Basophil · Eosinophil · Phagocytes (Neutrophil, Macrophage/Reticuloendothelial system)

Professional APCs: Dendritic cell · Macrophage · B cell
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Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Reticuloendothelial system".  Read more