Difference between revisions of "Monocytes"

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[[Image:LH Monocyte Histology.jpg|right|thumb|150px|<p>'''Monocyte'''</p><sup>©RVC 2008</sup>]]
 
[[Image:LH Monocyte Histology.jpg|right|thumb|150px|<p>'''Monocyte'''</p><sup>©RVC 2008</sup>]]
==Introduction==
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<p>Monocytes are the largest [[Leukocytes|leukocytes]]. They have a large indented nucleus, few granules and constitute about 5% of circulating [[Leukocytes|leukocytes]]. Monocytes are precursors to a number of cells that make up the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]]. Developing in the [[Bone Marrow - Anatomy & Physiology|bone marrow]], monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate.</p>
Monocytes are the largest [[Leukocytes|leukocytes]]. They have a large indented nucleus, few granules and constitute about 5% of circulating leukocytes. Monocytes are precursors to a number of cells that make up the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]]. Developing in the [[Bone Marrow - Anatomy & Physiology|bone marrow]], monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate.
 
 
 
 
==Development==
 
==Development==
<p>Monocytes develop from the bi-potential [[Haematopoiesis - Overview#Colony Forming Units|CFU-GM]] stem cell during [[Leukopoiesis|leukopoiesis]].</p>
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<p>Monocytes develop from the bi-potential [[Overview of Haematopoiesis - WikiBlood#Colony Forming Units|CFU-GM]] stem cell. Further details of this process ([[Leukopoiesis - WikiBlood|leukopoiesis]]) can be found [[Leukopoiesis - WikiBlood#Monocyte development|here]].</p>
<p>When monocytes leave the blood stream they then differentiate into a number of cells (all are classified as [[Macrophages|macrophages]]):
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<p>When monocytes leave the blood stream they then differentiate into a number of cells (all are [[Macrophages|macrophages]]):
 
* Connective tissue histiocyte
 
* Connective tissue histiocyte
 
* [[Respiratory System General Introduction - Pathology#Alveolar macrophages|Alveolar macrophage]]
 
* [[Respiratory System General Introduction - Pathology#Alveolar macrophages|Alveolar macrophage]]
 
* Peritoneal macrophage
 
* Peritoneal macrophage
* Liver Kupffer cell  
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* Kupffer cell of [[Liver - Anatomy & Physiology|liver]]
 
* Melanophage of skin
 
* Melanophage of skin
 
* Lipophage
 
* Lipophage
 
* [[Bones - Anatomy & Physiology#Osteoclasts|Osteoclasts]] in bone
 
* [[Bones - Anatomy & Physiology#Osteoclasts|Osteoclasts]] in bone
* [[Neurons_- Anatomy & Physiology#Microglial_Cells|Microglial cell]] in bone & brain
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* Microglial cell in bone & brain
 
* Specialised histiocytes
 
* Specialised histiocytes
 
** Epithelioid cell
 
** Epithelioid cell
 
* Histiocytic giant cell
 
* Histiocytic giant cell
** Langerhans cell
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** Langhan’s cell
** Touton giant cell</p>
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** Foreign body
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** Touton</p>
 
[[Image:Monocyte Picture.jpg|thumb|right|150px|Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
 
[[Image:Monocyte Picture.jpg|thumb|right|150px|Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
  
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<p>Monocytes can live for months to years in the circulation.</p>
 
<p>Monocytes can live for months to years in the circulation.</p>
 
<p>Monocytes are referred to as macrophages once they enter a tissue by '''diapedesis'''.</p>
 
<p>Monocytes are referred to as macrophages once they enter a tissue by '''diapedesis'''.</p>
<p>Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to [[T cells]].</p>
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<p>Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to [[Lymphocytes#T cells|T cells]].</p>
==Monocytosis==
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===In pathology===
An increase in the number of monocytes (haematogenous macrophages) in the blood is known as a [[Monocytosis|monocytosis]]. It occurs in conjunction with other changes inidicative of a [[Stress Leucogram|stress leucogram]] or it may occur independently. Monocytes in the blood represent a brief transitional stage as they quickly move into tissues and differentiate further to tissue macrophages; they rarely perform any notable functions whilst in the bloodstream but they have been found to phagocytose red blood cells in cases of immune-mediated haemolytic anaemia. The major causes of monocytosis are:
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*[[Changes in Inflammatory Cells Circulating in Blood - Pathology#Monocytosis|Monocytosis]]
*Stress leucogram mediated by the production or administration of glucocorticoids (plus a neutrophilia, eosinopenia and lymphopenia).
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<br>
*Chronic inflammatory processes, including chronic bacterial infections and chronic inflammatory diseases of the liver (chronic hepatitis and cholangitis) and pancreas (chronic pancreatitis).
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*Granulomatous disease results in monocytosis as monocytes are recruited to contain certain types of bacteria (namely Mycobacteria spp., Nocardia spp., Actinomyces and Rhodococcus equi) or foreign bodies.
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<center><b><sup>Blood cells: [[Erythrocytes|Erythrocytes]] |
*Certain types of monocytic or myelomonocytic chronic myeloid leukaemia may result in the presence of large numbers of monocytes in the blood.
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[[Basophils|Basophils]], [[Eosinophils|Eosinophils]], [[Lymphocytes|Lymphocytes]], [[Macrophages|Macrophages]], [[Mast Cells|Mast cells]], [[Monocytes|Monocytes]] & [[Neutrophils|Neutrophils]] |  [[Thrombocytes|Thrombocytes]] & [[Thrombopoiesis#Megakaryocyte|Megakaryocytes]]</sup></b></center>
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[[Category:Blood_Cells]] [[Category:Kate English reviewing]]
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[[Category:WikiBlood]]

Revision as of 12:57, 12 June 2010

Monocyte

©RVC 2008

Monocytes are the largest leukocytes. They have a large indented nucleus, few granules and constitute about 5% of circulating leukocytes. Monocytes are precursors to a number of cells that make up the mononuclear phagocytic system. Developing in the bone marrow, monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate.

Development

Monocytes develop from the bi-potential CFU-GM stem cell. Further details of this process (leukopoiesis) can be found here.

When monocytes leave the blood stream they then differentiate into a number of cells (all are macrophages):

  • Connective tissue histiocyte
  • Alveolar macrophage
  • Peritoneal macrophage
  • Kupffer cell of liver
  • Melanophage of skin
  • Lipophage
  • Osteoclasts in bone
  • Microglial cell in bone & brain
  • Specialised histiocytes
    • Epithelioid cell
  • Histiocytic giant cell
    • Langhan’s cell
    • Foreign body
    • Touton

Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS

Action

During inflammation chemokines attract monocytes which migrate out of blood vessels into the damaged tissue, where they differentiate into cells of the mononuclear phagocytic system.

Monocytes can live for months to years in the circulation.

Monocytes are referred to as macrophages once they enter a tissue by diapedesis.

Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to T cells.

In pathology



Blood cells: Erythrocytes | Basophils, Eosinophils, Lymphocytes, Macrophages, Mast cells, Monocytes & Neutrophils | Thrombocytes & Megakaryocytes