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GRANULOPOIESIS

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GRANULOPOIESIS

• Granulopoiesis (or granulocytopoiesis) is hematopoiesis of granulocytes. The blood granulocytes and monocytes are formed in the bone marrow from a common precursor cell (figure 5).

3Figure 5

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Control of granulopoiesis: myeloid growth factors

• The granulocytes series arises from bone marrow progenitor cells which are increasingly specialized. – Many growth factors are involved in this

maturation process including interleukin-1 (IL-1), IL-3, IL-5 (for eosinophils), IL-6, IL-11, granulocyte macrophag colony-stimulating factor (GM-CSF), granulocyte CSF (G-CSF) and monocyte CSF (M-CSF).

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The function of granulocytes

1. Chemotaxis (Cell mobilization and migration)• The phagocyte is attracted to bacteria or the

site of inflammation• by chemotactic substances released from

damaged tissues • by complement components also • by the interaction of leukocyte adhesion

molecules with ligands on the damaged tissues

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2. Phagocytosis• Recognition of a foreign particle is aided by

opsonization with immunoglobulin or complement (both neutrophils and monocytes have Fc and C3b receptors)

3. Killing and digestionOxygen-dependent and oxygen-independent pathways. In the oxygen-dependent reactions:

• Superoxide (O2),• Hydrogen peroxide (H2O2) and • Other activated oxygen (O2) species, are

generated from O2 and

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– In neutrophilsm;• H2O2 reacts with myeloperoxidase to kill

bacteria; • Activated oxygen may also be involves a

fall in pH within phagocytic vacuoles into which lysosomal anzymes are released.

• Lactoferrin – an iron binding protein present in neutrophil granules – is bacteriostatic by depriving bacteria of iron.

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– In the oxygen-independent• Although more than two dozen factors

have been implicated in control of the macrophages response to inflammation, five of these are believed to play dominant roles.

• They are consist of :1. tumor necrosis factor (TNF),

2. interleukin-1 (IL-1),

3. granulocyte-monocyte colony stimulating factor (GM-CSF),

4. granulocyte colony stimulating factor (G-SCF),

5. monocyte colony stimulating factor (M-CSF).

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• These factors are formed by activated macrophage cells in the inflametd tissues and

• In smaller quantities by other inflamed tissue cells.