Physiological Functions
of
White Blood cells
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Objectives: WBCs
1. Identify the different types of WBCs
2. Enumerate the functions of the various types of
WBCs
3. Describe the steps of formation of WBCs
4. List the factors required for their maturation.
5. Infer the importance of total and differential
WBC counts
6. Define the terms leucocytosis and leucopenia
7. Define leukemia
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White Blood Cells (WBCs)
Total Leucocyte count (TLC)
4000-11,000 /μL
Types of WBCs
Granulocytes contain granules
Neutrophils
Eosinophils
Basophils:
Agranlocytes
Lymphocytes
Monocytes
Differential count: DLC
Neutrophils 60-70%
Lymphocytes 20-25%
Monocytes
3-8%
Eosinophils
1-4%
Basophils
0-1%
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Neutrophils 60-70%
•10-12 µ in size; 2-5 lobed nucleus; Older the cell more the lobes(polymorphonuclear leukocytes);
•Small colored granules which contain enzymes, Defensins, oxidants
•Action: by Phagocytosis
•Life span: a few hrs: 4-8 hrs in blood; 4-5 days in tissues
•Fast response; neutrophilia in bacterial diseases; neutropenia in drug toxicity
Eosinophils
0-4%; 10-12 µ
Bi-lobed nucleus; coarse acidophilic granules
Phagocytose antigen-antibody complexes; destroy parasites
Granules contain various enzymes : MBP
Increase in allergic conditions; decrease during stress-corticoids
Basophils 0-1% 8-10 µ
Nucleus usually bi-lobed;
large deep purple colored granules which often cover the nucleus
Secrete heparin, serotonin, histamine: help in inflammation
The Granulocytes
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Agranular WBCs
Monocyte 12-20 µ;3-8%; circulate in blood for about 20-30 hrs.
long life span (many weeks to months) after change into macrophages in
tissues
Single kidney shaped nucleus
Phagocytosis after converting in to macrophages
Lymphocyte 6-9 µ (small); 10-14 µ (large); 20-25%; mostly formed in
lymhoid tissue; some in bone marrow.
Nucleus surrounded by thin ring of cytoplasm; long life span inside tissues,
but only a few hours in blood
B and T lymphocytes: Immune mechanisms
B lymphos form plasma cells
Natural Killer (NK) cells against viruses, cancer
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Physiology and Functions of WBCs

Life span: few hours to a few days
They have Major Histocompatibility Antigens on surface:
-Identification of the “SELF”

Main functions:


combat infection by phagocytosis
immune mechanisms

Adhesion molecules


Selectins: on endothelial cells - attach to CHOn
on neutrophil

surface
Integrins on neutrophils: also make
WBCs stick to endothelial surface, &
help them to move out of the blood vessels

When required , they escape from the blood via
capillary pores (emigration) helped by integrins
enter tissue and have their action there by
phagocytosis
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Phagocytosis


Mainly by neutrophils and monocytes
Steps of Phagocytosis
1 . Chemotaxis : attraction of WBCs to site of infection
Promoted by
i. bacterial toxins
ii. kinins from damaged tissues
iii. CSFs
2. Adherence
phagocyte attaches to microbe using proteins
3. Ingestion
pseudopods from WBC surrounds microbe
formation of a PHAGOSOME
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4. Digestion
Phagosome enters cytoplasm of WBC and merges with LYSOSOME: Phagolysosome: secretion of lysozomal enzymes followed by release of oxidants:
oxidative burst
5. Killing as result of the above. Residual bodies get left behind
1 CHEMOTAXIS
Microbe
Phagocyte
2 ADHERENCE
3 INGESTION
Pseudopod
Lysosome
Plasma
membrane
4 DIGESTION
5 KILLING
Digestive
enzymes
Digested microbe
in phagolysosome
Residual body
(indigestible
material)
Phases of phagocytosis
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Formation of WBCs: Hemopoiesis
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Pluripotent stem cell
Lymphoid stem cell
Myeloid stem cells
Colony Forming Unit
G/M
Eosinophilic
myeloblast
Basophilic
myeloblast
•
Neutrophil
monocyte
T
lymphocyte
T lymphoblast
eosinophil
B
lymphocyte
B lymphoblast
NK lymphoblast
basophil
NK
Cell
Granulocytes and monocytes : formed only in the BONE MARROW stored in the bone marrow, and
released into circulation. Lympocytes and Plasma cells also in lymhoid tissue, are stored in lymhoid
tissue . Few released into circulation
• Various Colony Stimulating factors (CSFs or Growth Inducers) help in their formation:
IL1, IL6 and IL3 (multi CSF)
These are proteins in nature
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Normal WBC count: 4000-11000
Leuocytosis >11000
Leuopenia < 4000
Neutophils
Infections, Burns, inflammation
Lymphocytes
Viral infections
Monocyts
Viral, fungal infections, TB,
Chronic disease
Some viral infections
Bacterial infections (typhoid)
Bone marrow suppression
Drugs: antibiotics
corticosteroids
Eosinophils
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Typical eg:
8 year child; high fever;
pain throat; difficulty in swallowing
swollen septic tonsils
TLC 18,500
DLC: N. 88%; L 10%; E 2%
Elderly person; exposure to radiation
Hx of intractable fever and infections;
Loss of appetite
Leukemias
(blood cancer)
TLC 2000
DLC: N. 30% L 60%; E 4% ;
6% other WBCs
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Summary
1. TLC, types of WBC, DLC
2. Description of various types of WBCs and their actions
3. Phagocytosis
4. Development of WBCs and factors associated
5. Define leucocytosis/leucopenia with typical examples
6. Leukemias or blood cancer
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