This document summarizes the process of leukopoiesis, or white blood cell formation. It describes the myeloid and lymphoid stem cell lineages that give rise to granulocytes, monocytes, and lymphocytes. The key stages of development are discussed, from pluripotent stem cells into committed progenitor cells, blast cells, promyelocytes/promonocytes, myelocytes, metamyelocytes, and band or segmented mature forms. Cytokines such as colony stimulating factors regulate white blood cell development and differentiation. Leukocytes mature over 10 days, spending half that time dividing and half maturing, before circulating and taking on tissue-specific functions.
2. OBJECTIVES
To get a better understanding of :
Myeloid series and lymphoid series
Progenitor cells
Blast cells
Promyelocytes and promonocytes
Myelocytes and Metamyelocytes
Band form of neutrophils
Factors regulating leucopoiesis
Life history of leukocytes
3. INTRODUCTION
⩥ The process of development and
maturation of Leukocytes is called
Leukopoiesis.
⩥ It is a part of Hemapoeisis (formation of
Blood cells ).
⩥ All Blood cells develop from Pluripotent
Hemapoeitic stem cells.
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5. INTRODUCTION
⩥ They are formed partially in the bone
marrow (granulocytes, monocytes and a
few lymphocytes) and partially in the
lymph tissue (lymphocytes and plasma
cells).
⩥ After formation, they are transported in
the blood to different parts of the body
where they are needed.
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6. INTRODUCTION
There are two series of leukocytes :
Myeloid series and
Lymphoid series.
Myeloid series matures into granulocytes
and monocytes.
Lymphoid series matures into
lymphocytes.
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9. ⩥ The pluripotent stem cells in the
bone marrow give rise to committed
stem cells.
⩥ The committed stem cells are
broadly classified into two types :
Myeloid stem cells and Lymphoid
stem cells.
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10. MYELOID SERIES
⩥ The stem cells for myeloid series are
trilineage stem cells that form stem cells
for three series of blood cells.
Erythroid series for red cells
Megakaryoid series for
platelets
Stem cells for granulocyte –
monocyte series
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12. PROGENITOR CELLS
⩥ The stem cells of granulocyte –
monocyte series of myeloid series give
rise to three categories of progenitor cells
– Colony Forming Units (CFUs)
CFU – GM
CFU – Eo
CFU - Bas
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13. CONTD..
CFU – GM : on further differentiation form CFU
– G for Neutrophils and CFU – M for
Monocytes.
CFU – Eo : Eosinophil lineage
CFU – Bas : Basophil lineage
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14. BLAST CELLS
⩥ The CFUs form blast cells.
⩥ CFU – G forms myeloblasts which on further
development form neutrophils.
⩥ CFU – M forms monoblast that develops into
monocytes.
⩥ CFU – Eo forms eosinophil – myeloblast that
develops into eosinophils.
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15. CONTD..
⩥ CFU – Bas forms basophil – myeloblast that
develops into basophils.
⩥ The blast cells are large cells 16 – 20 µm, with
large nucleus containing multiple nucleoli.
⩥ The nucleoli are prominent features of blast
cells and are the sites of assembly of ribosomal
proteins and r-RNA.
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16. CONTD..
⩥ The cytoplasm is scanty.
⩥ The cells are actively mitotic.
⩥ Myeloblasts
The earliest precursor cells for
neutrophils are myeloblasts.
They have scanty blue cytoplasm with 5
– 10 nucleoli in a large nucleus.
There are separate myeloblasts for
eosinophils and basophils.
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18. CONTD..
⩥ Monoblasts
These are blast cells for monocytes.
Since they resemble myeloblasts
morphologically, they are also called
myelomonoblasts.
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20. Promyelocytes and promonocytes
⩥ Myeloblasts give rise to promyelocytes and
promonocytes develop from monoblasts.
⩥ They have the following features :
Size : 15 – 20 µm
The cells are large and cytoplasm is
granular.
Nucleus – round, condensed and
contains less nucleoli (1-2)
Cells are mitotic. 20
21. CONTD..
⩥ Promonocytes are larger cells and on further
development form monocytes which are the
largest cells.
⩥ Monocytes form macrophages and Dendritic
cell.
⩥ Promyelocytes are also larger cells and contain
peroxidase-positive granules.
⩥ The granules are large in size with diameter of
500 nm.
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23. MYELOCYTES
⩥ Promyelocytes give rise to myelocyes.
⩥ They have the following features :
Size : 12 – 20 µm
Cytoplasm : fine specific granules
which are peroxidase negative.
Granules are 200 nm and are
spherical or rod shaped
Nucleus : round, concentric
Nucleoli are absent.
Some degree of Mitosis occurs. 23
25. METAMYELOCYTES
⩥ Metamyelocytes develop from
myelocytes
⩥ Size : 12 – 18 µm.
⩥ Cytoplasm : Numerous fine mixed
granules.
⩥ Nucleus : Eccentric, Kidney shaped.
⩥ No mitosis.
⩥ Give rise to band form of neutrophils,
eosinophils and basophils.
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27. BAND FORM
⩥ Neutrophils that develop from metamyelocytes
are juvenile neutrophils (band forms) that
further grow into matured or segmented
neutrophils.
⩥ Size : 10 – 14 µm
⩥ Cytoplasm : Granular
⩥ Nucleus : U shaped or Horse shoe shaped.
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29. LYMPHOID SERIES
⩥ Lymphoid stem cells give rise to Lymphoblasts
⩥ Lymphoblasts have the following features :
Size is 10 – 20 µm
Fewer nucleoli
more condensed nuclear chromatin
Absence of cytoplasmic granules.
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30. Contd..
⩥ Lymphoblasts give rise to B cell, T cell and NK
cells (Lymphocytes).
⩥ T cells leave the bone marrow
and mature in the thymus.
⩥ Some of the B cells
differentiate to form
plasma cells.
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32. Regulation of leukopoiesis
⩥ Leukopoiesis is mainly regulated by cytokines
especially, colony – stimulating factors (CSFs),
Interleukins (ILs) and Tumor Necrosis Factor
(TNF)
⩥ T lymphocytes, monocytes, fibroblasts,
endothelial cells, liver and kidney are the main
sources of Hemopoietic Growth Factors (HGFs)
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33. INTERLEUKINS
⩥ IL – 1, IL – 6 and IL – 3 promote
maturation of stem cells.
⩥ IL – 5 helps in the development of eosinophils
hence called eosinophilic growth factor.
⩥ IL – 3 & 4 facilitate development of Basophils
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34. COLONY STIMULATING FACTORS
⩥ GM – CSF, G – CSF and M – CSF are the main
CSFs.
⩥ GM – CSF :
secreted by fibroblasts, vascular
endothelial cells, monocytes and T –
lymphocytes.
stimulates differentiation and
proliferation of pluripotent stem cells into
committed cells.
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35. CONTD..
⩥ G – CSF :
Produced by monocytes, endothelial
cells and fibroblasts.
Helps in development and functions of
granulocytes.
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36. CONTD..
⩥ M – CSF:
Also called CSF – 1
Promotes proliferation of monocytes
and macrophages and also stimulates
functions of monocytes.
TNF : help in proliferation and differentiation of
stem cells.
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37. LIFE HISTORY
⩥ Marrow phase : mitotic pool and maturation
pool.
The development from myeloblasts to
myelocytes constitute the mitotic pool
Maturation of metamyelocytes into
mature cells constitute the maturation
pool
5 days in mitotic pool , 5 days in
maturation pool
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38. CONTD..
⩥ Circulation phase : 50 % margination pool, 50 %
circulation pool.
⩥ Tissue phase : undergo apoptosis , monocytes
to macrophages.
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APPLIED ASPECT
IN EXERCISE LEUKOCYTOSIS
OCCURS DUE TO DISRUPTION OF
THE MARGINATION OF LEUKOCYTES.