WBC

1. White blood cells
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
RDGMC
DR Sai Sailesh Kumar G 1

2. Learning objectives
 Classify white blood cells
 List stages of leucopoiesis
 Describe the functions of white blood cells
 Describe physiological and pathological
variation of total white blood cells
 Describe the monocyte-macrophage system
and its functions
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3. Introduction
 Our bodies are exposed to bacteria, virus, fungi and
parasites, all of which occur normally and to varying
degrees in the skin, the mouth, respiratory passages,
intestinal tract, lining membranes of eyes and even
urinary tract
 Many of these infectious agents are capable of causing
serious abnormal physiological function or even death if
they invade deeper tissues
 Our body have a special system for combating the
different infectious and toxic agents
 This system is composed of blood leucocytes and tissue
cells derived from leucocytes
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4. Leucocytes (WBC)
 WBC are mobile units of the body’s protective
system
 They are formed partially in the bone marrow
(granulocytes and 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 DR Sai Sailesh Kumar G 4

5. General characteristics of Leucocytes
 Six types of white blood cells are normally present in the
blood
1. Polymorphonuclear neutrophis
2. Polymorphonuclear eosinophils
3. Polymorphonuclear basophils
4. Monocytes
5. Lymphocytes
6. Occasionally plasma cells
 The first three types of cells have granular appearance
 Polys – multiple nuclei
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6. Concentrations of different WBC’s in
blood
 Polymorphonuclear neutrophils – 62%
 Polymorphonuclear eosinophils – 2.3%
 Polymorphonuclear basophils – 0.4%
 Monocytes - 5.3%
 Lymphocytes – 30%
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7. DR Sai Sailesh Kumar G 7

8. Genesis of WBC
 Myelocytic lineages – begins with Myeloblast
 Lymphocytic lineage – begins with lymphoblast
 The granulocytes and monocytes are formed only in the
bone marrow
 Lymphocytes and plasma cells are produced mainly in
the various lymphogenous tissues –
1. especially lymph glands, spleen, thymus, tonsils
2. and various pockets of lymphoid tissues in the body
such as in bone marrow
3. and in so called Peyer’s patch underneath the
epithelium in the gut wall
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10. Genesis of WBC
 The WBC formed in the bone marrow are stored
within the bone marrow until they are needed in the
circulatory system
 When the need raises various factors cause them to
be released
 Normally about three times as many WBC are stored
in the marrow as circulate in the entire blood
 This represents about a 6 day supply of these cells
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11. Life span of granulocytes
 The life of granulocytes after being released
from bone marrow is normally 4-8 hours
circulating in the blood and another 4-5 days in
tissues where they needed
 In case of serious infections, the total life span is
often shortened to only few hours as the
granuloytes proceed more rapidly to the infected
area, perform their functions and in the process,
are themselves destroyed
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12. Life span of monocytes
 The monocytes also have a short transit time,
10-20 hours in blood
 Once they reach tissues, they swell too much
larger size to become tissue macrophages
 In this form they can live for months unless
destroyed while performing phagocytic
functions
 These tissue macrophages are the basis of the
tissue macrophage system
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13. Life span of lymphocytes
 Lymphocytes enter the circulatory system
continually, along with drainage of lymph from the
lymph nodes and other lymphoid tissue
 After few hours, they pass out of the blood back
into the tissues by diapedesis
 Then they re enter the lymph and return to the blood
again and again
 Thus, there is continual circulation of lymphocytes
through the body
 The life span is few weeks or months depending on
need of these cells DR Sai Sailesh Kumar G 13

14. Neutrophils and macrophages defend
against infections
 Mainly neutrophils and tissue macrophages attack and
destroy invading bacteria, viruses and other injurious
agents
 Neutrophils are mature cells that can attack and destroy
bacteria even in the circulatory blood
 Conversely, tissue macrophages begin life as blood
monocytes which are immature cells and have little
ability to fight infectious agents at that time
 Once they enter tissues, they begin to swell
 These cells are now called as macrophages which are
extremely capable of combating disease agents in
tissues DR Sai Sailesh Kumar G 14

15. Diapedesis
 Neutrophils and monocytes can squeeze
through the pores of the blood capillaries -
diapedesis
1) Even though a pore is much smaller than cell
2) Small portion of cell slide through the pore at a
time
3) The portion sliding through is momentarily
constricted to the size of the pore
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17. Ameboid motion
 Both neutrophils and macrophages can move
through the tissues by ameboid motion
 Some cells move at velocities as great as 40
micrometers/ minute
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18. Chemotaxis
 Many different chemical substances in the tissues
causes both neutrophils and macrophages to move
toward the source of the chemical
 This phenomenon is called chemotaxis
 These chemical substances include
1. Bacterial or viral toxins
2. Degenerative products of the inflamed tissues
3. Several reaction products of the complement
complex
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19. Phagocytosis
 Most important function of neutrophils and macrophages
is phagocytosis
 Phagocytosis – ingestion of offending agent
 Phagocytosis must be selective of the material
 Otherwise normal cells are ingested
 Phagocytosis occurs or not depends on three
procedures
1. Surface of tissues should be rough (normally smooth)
2. Dead tissues and foreign particles has no protective
coat ( normal cells have protective coat)
3. Immune system of the body
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20. Immune system
 Develops antibodies against infectious agents
 Antibodies adhere to bacterial membranes
 Antibodies combine with the c3 product of the
complement cascade
 C3 molecule in turn attach to the receptors of
phagocyte membrane
 Makes bacteria susceptible to phagocytosis
 This process by which a pathogen is selected for
phagocytosis and destruction is called opsonization
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21. Phagocytosis by neutrophils
 Neutrophils entering the tissues are already mature cells
 Can immediately begin phagocytosis
1. Neutrophil attaches to the foreign particle
2. Project pseudopodia in all the directions around the particle
3. Pseudopodia meet one another on opposite side and fuse
4. Creates an enclosed chamber that contains phagocytized
particle
5. Then the chamber invaginate to the inside of the cytoplasmic
cavity and breaks away from the outer cell membrane
6. Now the vesicle is called phagosome (inside cytoplasm)
7. A single neutrophil usually phagocytize 3-20 bacteria before
the neutrophil become inactivated and dies
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22. Phagocytosis by macrophages
 Macrophages are end products of monocytes
 Enter the tissue from blood
 They are much more powerful than neutrophils
 Capable of phagocytizing as many as 100 bacteria
 They also have ability to engulf much larger particle
even whole RBC or occasionally malaria parasites
 Neutrophils are not capable of phagocytizing
particles much larger than bacteria
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23. Digestion by intra cellular enzymes
 Once a foreign particle is phagocytized, lysosomes and other
cytoplasmic granules in neutrophils or macrophages immediately
come in contact with phagosome
 Their membranes fuse
 Dumping digestive enzymes (myeloperoxidase, catalyzes) into
phagosome
 Now phagosome become digestive vesicle
 Digestion of the phagocytized particle begins immediately
 Both neutrophil and macrophages contain lots of lysosomes filled
with proteolytic enzymes
 The lysosomes of macrophages (not neutrophils) contains large
amount of lipases, which digest the thick lipid membranes
possessed by some bacteria such as the tuberculosis bacillus
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24. Bactericidal agents
 some bacteria have protective coats that prevent action
of lysosomal digestive enzymes
 Neutrophils and macrophages contain bactericidal
agents which can kill bacteria even when the lysosomal
enzymes fail to digest them
 These agents are powerful oxidizing agents formed by
peroxisomes
 These oxidizing agents include superoxide, hydrogen
peroxide and hydroxyl ions which are lethal to most
bacteria.
 bacillus DR Sai Sailesh Kumar G 24

25. Tuberculosis bacillus
 have coats that resist to lysosomal digestion
 Also secrete substances that partially resist the
killing effect of neutrophils and macrophages
 These bacteria is responsible for many of the
chronic diseases, an example of which is
tuberculosis
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26. Eosinophils
 Constitute 2% of all the blood leucocytes
 Weak phagocytes
 Exhibit chemotaxis
 Produced in large number in people with
parasitic infections
 They migrates into tissues diseased by parasites
 Attach to the parasite surface
 Release substances that kill parasites
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27. Substances released by eosinophils
 hydrolytic enzymes from their granules
 Highly reactive forms of oxygen that is
especially lethal to parasites
 Releases major basic protein – larvicidal poly
peptide
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28. Most common parasitic infections
 One of the most wide spread parasitic infection
schistosomiasis – can invade any part of the body
 Another parasitic disease that cause eosinophilia is
trichinosis
 The disease result from invasion of body’s muscles
by the trichinella parasite (pork worm)
 When person eats undercooked infested pork
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29. Eosinophilia in allergic reactions
 Eosinophils collects in tissues where allergic reactions
occurs
 Peribronchial tissues in lungs in asthma patients
 Skin after allergic skin reactions
 When allergy occurs, mast cells and basophils release
eosinophilic chemotactic factor
 That cause eosinophils to migrate to allergic tissue
 Eosinophils detoxify the inflammation inducing
substance by mast cells and basophils
 Phagocytize and destroy allergen – antibody complexes
and prevent spread of inflammation
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30. Basophils
 Similar to mast cells
 Mast cells and basophils plays an important role in
allergic reactions
 IgE antibody that cause allergic reactions binds with
these cells
 Rupture of mast cells and basophils
 Release large quantities of histamine, heparin,
bradykinin and serotonin, slow reacting substance
of anaphylaxis
 Cause local vascular and tissue reactions
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31. Lymphocytes
 T lymphocytes – cellular immunity (helper, memory,
cytotoxic T cells)
 B lymphocytes – humoral immunity ( plasma cells
secreting antibodies)
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32. leukopenia
 Rarely occurs
 Bone marrow produces very few WBC’s
 body becomes unprotected against many bacteria and other
agents
 Normally human body lives in symbiosis with many bacteria
because all the mucous membranes of the body are
constantly exposed to large number of bacteria
 Mouth almost always contains various spirochetal,
pneumococcal and streptococcal bacteria
 These bacteria also present in respiratory tract (lesser extent)
 Distal GIT is especially loaded with colon bacilli
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33. leukopenia
 One can find bacteria on the surface of eyes, urethra.
 Decrease in WBC
 Within 2 days after the bone marrow stops producing
WBC
 Immediately allows invasion of adjacent tissues by
bacteria that are already present
1. Ulcers occur in mouth and colon
2. Severe respiratory infections may develop
 If not treated death occurs in less than a week after acute
leukopenia DR Sai Sailesh Kumar G 33

34. Cause for leukopenia
 irradiation of the body by x-rays or gamma rays
 Exposure to drugs and chemicals that contain benzene
 Cause aplasia of bone marrow
 Also –
1. Common drugs such as chloramphenicol (antibiotic)
2. Thiouracil (used to treat thyrotoxicosis)
3. Barbiturate hyptonics
 Cause leukopenia
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35. Leukemia
 Uncontrolled production of WBC
 Greatly increased abnormal WBC in the blood
 Cancerous mutation of myelogenous or
lymphogenous cells
 Two types
1. Lymphocytic
2. Myelogenous
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36. Lymphocytic Leukemia
 Cancerous production of lymphoid cells
 Begins in lymph node or other lymphoid tissue
 Spread to other areas of the body
Myelogenous leukemia
 Begins by cancerous production of myelogenous cells in
the bone marrow
 Spread throughout the body
 WBCs are produced in many extra medullary tissues
1. Lymphnodes
2. Spleen and liver
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37. Effects of leukemia on the body
 Metastatic growth of Leukemic cells in abnormal
areas of body
 Leukemic cells invade the surrounding bone and
cause pain, bone fractures
 Development of infection
 Severe anemia
 Bleeding tendency caused by thrombocytopenia
 Displacement of normal bone marrow and lymphoid
cells by non functional leukemic cells
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38. Effects of leukemia on the body
 Important effect of leukemia on the body is excessive use of
metabolic substrates by the growing cancerous cells
 Leukemic tissues reproduce new cells so rapidly that tremendous
demands are made on the body reserves for food stuffs, specific
amino acids, vitamins.
 Energy of patient is greatly depleted
 Excessive use of proteins by leukemic cells cause rapid
deterioration of normal protein tissues of body
 While leukemic tissues grow, other tissues become debilitated
 After, metabolic starvation has continued long enough, this alone is
sufficient to cause death
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39. Reticuloendothelial system
 Monocyte-macrophage cell system
 Macrophages are mobile cells that are capable of
wandering through the tissues
 A portion of monocytes convert into macrophages
once they enter tissues
 Another portion of monocytes becomes attached to
the tissues and remain attached for months or until
years until they are called on to perform protective
functions
 These monocytes have same phagocytic capability
as macrophages DR Sai Sailesh Kumar G 39

40. Reticuloendothelial system
 The combination of monocytes, macrophages, few
specialized endothelial cells in the bone marrow, spleen,
lymph nodes is called reticulo-endothelial system
 However, all these cells originate from monocyte stem
cells
 Therefore, the retiulo endothelial system is almost
synonymous with monocyte-macrophage system
1. Tissue macrophages in the skin and subcutaneous
tissues
2. Macrophages in lymph nodes
3. Alveolar macrophages
4. Macrophages in liver sinusoids (kupffer cells)
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42. THANK YOU
DR Sai Sailesh Kumar G 42