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Monocytes
Last reviewed: 05.07.2025
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Monocytes are formed in the red bone marrow from monoblasts. After leaving the bone marrow, where, unlike granulocytes, they do not form a bone marrow reserve, monocytes circulate in the blood for 36 to 104 hours, and then go into the tissues. 7×10 6 monocytes leave the blood for the tissues in 1 hour. In the tissues, monocytes differentiate into organ- and tissue-specific macrophages. The extravascular pool of monocytes is 25 times greater than the circulating one.
The mononuclear phagocyte system unites various types of cells involved in the body's defense reactions. Macrophages play a key role in phagocytosis processes. They remove dying cells, remains of destroyed cells, denatured protein, bacteria, and Ag-AT complexes from the body. Macrophages participate in the regulation of hematopoiesis, immune response, hemostasis, lipid and iron metabolism.
Reference values for absolute and relative monocyte counts in the blood
Age |
Absolute quantity, ×10 9 /l |
Relative quantity,% |
12 months |
0.05-1.1 |
2-7 |
4 years |
0-0.8 |
2-7 |
10 years |
0-0.8 |
1-6 |
21 years old |
0-0.8 |
1-8 |
Adults |
0-0.8 |
1-8 |
Causes of increase and decrease of monocytes
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