What is the Reticuloendothelial System?

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  • Originally Written By: Dulce Corazon
  • Revised By: C. Mitchell
  • Edited By: C. Wilborn
  • Last Modified Date: 03 December 2018
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The reticuloendothelial system, also known as the macrophage system or the mononuclear phagocyte system, is a network of cells located throughout the body that help filter out dead and toxic particles and also work to identify foreign substances in both the blood and tissues. The network is an important part of the larger immune system, and helps maintain healthy organ function and blood chemistry, too. Though these sorts of cells can be found in most parts of the body, they are often particularly dense in the spleen, an organ tasked with blood balance and purification.

Filtering and Destroying

Cells in the reticuloendothelial system (RES) typically have one of two main functions: they either filter out and destroy other particles and dead cells, or they identify foreign substances for presentation and cataloging. So-called “destroyer” cells are often referred to by the name “phagocytes.” These are capable of engulfing cells whole, preventing them from causing harm to the body.

Sometimes phagocytes focus on cells that are abnormal, old, or dead; in this case, they are sort of like trash removers. These cells usually also remove foreign matter that could be harmful, like bits of thread left from surgical sutures or flecks of metal from an accident. In other instances they actually attack viruses and bacteria, neutralizing their power to infect and cause damage.


When phagocytes group together or grow very large, they are usually called “macrophages.” Most macrophages are stationary, which means that they anchor themselves to one place and conduct their filtering and destruction in that zone only. Sometimes they move around, though most of the more mobile cells in the system are actually on immune patrol.

Immune Presentation

Foreign particles, particularly viruses and bacteria, usually need to be cataloged and identified in the larger immune system in order for the body to be able to identify them and build up defenses to them. Cells in the RES that aren’t attacking problem particles are usually identifying them and describing them in order to make a cataloged entry and help the body build up an immune response.

Cells known as “lymphocytes” are a common example. Lymphocytes capable of remembering specific foreign substances and they render protection by attacking these specific bacteria and viruses every time they enter the body. After identifying problem, they secrete specific antibodies for the problems they’ve identified. As such, they only attack problems they know — they don’t do general “trash collection” or cleanup.

Where They’re Found

RES cells are located throughout the body in various different organs and tissues and are present in most parts of the bloodstream, though they do appear in some places more predominantly than others. Their location often dictates their size and precise shape, and sometimes even warrants a special name.

Kupffer cells are found in the liver, for instance, while the same sorts of cells in the brain are known as microglia. When found in the lymph nodes, bone marrow, and spleen, they go by the more general “reticular cells” name. Tissue histiocytes or fixed macrophages are those located in the subcutaneous tissues, and when they’re in the lungs they are known as alveolar cells.

The Spleen’s Special Role

The spleen usually has a particularly vital function in the RES. This organ is specially designed to filter the blood, making sure that deformed and old cells are removed from circulation and broken down while maintaining the hemoglobin count of red blood cells. The spleen and the cells it contains play a major role in immune function and disease and infection prevention.

People can usually survive without this organ, as is often the case after an accidental rupture or other trauma, and sometimes the cells working here either slow down or grow dysfunctional which can necessitate removal. When this happens the entire RES usually has to start working harder in other parts of the body to compensate. Infection does pose a greater risk under these circumstances, though, and exhaustion and system failure are more likely, too. When the cells in the RES grow confused or tired they are more likely to make mistakes, which can lead to more infections, waste buildup in the blood, and a number of potentially serious complications.


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Post 4

Is is important in the metabolism of bilirubin, for example

Post 2

@elizabeth23 not only that, but they are necessary for helping the body properly fight off viruses and bacteria. The confusion of this system is one of the things which can contribute to a failed immune system, one which either releases antibodies improperly or does not release them at all.

Post 1

Phagocytic cells are like the body's waste management system. Without them, as this article shows, many parts of the body risk being filled with waste and other harmful substances.

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