LEC 3
Nada Mohamed Ahmed ,
MD, MT (ASCP)i
Objectives
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Definition
Types of leucocytes
Leucopoiesis stages
Normal morphology of WBCs (structure
&function)
Definition
• leukopoiesis – production and
developments of white blood
cells(leucocytes)
Leukopoiesis
Pluripotent
stem cell
Colony-forming
units (CFUs)
Mature
cells
Precursor
cells
leaves
Eosinophilic
CFU
Eosinophilic
myeloblast
Eosinophilic
promyelocyte
Eosinophilic
myelocyte
Eosinophil
Basophilic
CFU
Basophilic
myeloblast
Basophilic
promyelocyte
Basophilic
myelocyte
Basophil
Neutrophilic
CFU
Neutrophilic
myeloblast
Neutrophilic
promyelocyte
Neutrophilic
myelocyte
Neutrophil
Monocytic
CFU
Monoblast
Promonocyte
B prolymphocyte
Lymphocytic
CFU
Lymphoblast
Monocyte
B lymphocyte
T prolymphocyte
T lymphocyte
NK prolymphocyte
NK cell
White Blood Cells (Leukocytes)
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Formation of Leukocytes (Leukopoiesis):
All in bone marrow
Pluripotent stem cells
Myeloblast
lymphoblast
↓
↓
Myeloid line
Lymphoid line
- Granulocytes
Lymphocytes
- Monocytes
Formation of Leukocytes
Figure 18.11.2
Formation of Leukocytes
• All leukocytes originate from hemocytoblasts
• Hemocytoblasts differentiate into myeloid stem cells
and lymphoid stem cells
• Myeloid stem cells become myeloblasts or monoblasts
• Lymphoid stem cells become lymphoblasts
• Myeloblasts develop into eosinophils, neutrophils, and
basophils
• Monoblasts develop into monocytes
• Lymphoblasts develop into lymphocytes
Formation of Leukocytes
leukopoiesis – production of white blood cells
pluripotent stem cells – (PPSCs)
myeloblasts – form neutrophils,
eosinophils, basophils
monoblasts - form monocytes
lymphoblasts give rise to all forms of
lymphocytes
Production of Leukocytes
• Leukopoiesis is hormonally stimulated by two
families of cytokines (hematopoetic factors) –
interleukins and colony-stimulating factors
(CSFs)
– Interleukins are numbered (e.g., IL-1, IL-2), whereas
CSFs are named for the WBCs they stimulate (e.g.,
granulocyte-CSF stimulates granulocytes)
• Macrophages and T cells are the most important
sources of cytokines
• Many hematopoietic hormones are used clinically
to stimulate bone marrow
Types of Leukocytes
• Granulocytes
Neutrophils (60-70%)-polymorphonuclear
leukocytes
• barely-visible granules in cytoplasm; 3 to 5
lobed nucleus
Eosinophils (2-4%)
• arge rosy-orange granules; bilobed nucleus
Basophils (<1%)
• large, abundant, violet granules
(obscure a large S-shaped nucleus)
Granulocytes
10 µm
Neutrophils
Eosinophil
10 µm
Basophil
10 µm
Agranulocytes
Agranulocytes
lymphocytes (25-33%)
variable amounts of bluish cytoplasm (scanty to
abundant); ovoid/round, uniform dark violet
nucleus
monocytes (3-8%)
largest WBC; ovoid, kidney-, or horseshoeshaped nucleus
Agranulocytes
Monocyte
Lymphocyte
10 µm
10 µm
Characteristics of Mature Leukocytes (WBCs)
• Least Abundant Formed Element
– 5,000 To 10,000 Wbcs/L
• Protect Against Infectious Microorganisms And Other
Pathogens
• Conspicuous Nucleus
• Spend Only A Few Hours In The Blood Stream Before
Migrating To Connective Tissue
• Retain Their Organelles For Protein Synthesis
• granules
– All WBCs have lysosomes called nonspecific (azurophilic)
granules – inconspicuous so cytoplasm looks clear
– Granulocytes have specific granules that contain enzymes and
other chemicals employed in defense against pathogens
Leucocytes migration
• Circulating Wbcs Do Not Stay In Bloodstream
– granulocytes leave in 8 hours and live 5 days longer
– Monocytes leave in 20 hours, transform into
macrophages and live for several years
– Lymphocytes provide long-term immunity (decades)
being continuously recycled from blood to thymus gland
and back to the blood
Granulocyte Functions
• Neutrophils
– phagocytosis of bacteria
– release antimicrobial chemical
increased numbers in bacterial infections
• Eosinophils
initiate allergic reaction
– release enzymes to destroy large parasite
– increased numbers in parasitic infections
• Basophils
– secrete histamine (vasodilator) – speeds flow of blood to an
injured area
– produce inflammatory mediators
Agranulocyte Functions
• Lymphocytes
– destroy cells (cancer, foreign, and virally infected cells)
– coordinate actions of other immune cells
– secrete antibodies and provide immune memory
increased numbers in viral infections and inflammation
• Monocytes
– leave bloodstream and transform into macrophages
• phagocytize pathogens and debris
• “present” antigens to activate other immune cells antigen presenting cells (APCs)
• increased numbers in diverse infections and immune
responses
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