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10/25/2014
1
Leukocytes (White Blood Cells)
Medical Physiology, Guyton/Hall, 12th ed, Chapter 33
Mary C. Karlet
2015
Leukocytes
• Mobile units that work to prevent disease and infection
– Destroy invading agents by phagocytosis
– Form antibodies and sensitized lymphocytes, which also destroy the invader
– Upon release, wbc’s are transported in the blood to the area where they are needed
– Normal wbc count = 4,000 to 10,000 cells/mm3
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Leukocytes – Six Types
1. Neutrophils
2. Eosinophils
3. Basophils
4. Monocytes → tissue macrophages
5. Lymphocytes (“T” and “B”)
6. Plasma cells
Granulocytes“polys”
Genesis of WBC’s
1. pluripotent stem
cell
3. megakaryocyte
7. neutrophil
10. eosinophil
12. basophil
13-16. stages of
monocyte
formation
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Leukocytes
• Granuloctes and monocytes ingest invading organisms (bacteria, viruses, etc.) by phagocytosis
• Lymphocytes and plasma cells function as part of acquired immunity
• Formed and stored in bone marrow: – Granulocytes and monocytes
• “Formed” in lymph tissue (thymus, tonsils, lymph nodes, spleen)– Lymphoctes and plasma cells
Leukocyte Values in Peripheral Blood
Neutrophils 1800-7200 cells/mm3 55%
Lymphocytes 1500-4000 cells/mm3 36%
Eosinophils 0-700 cells/mm3 2%
Basophils 0-150 cells/mm3 1%
Monocytes 200-900 cells/mm3 6%
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Important Definitions
• Chemotaxis ≡ chemical
released from inflamed tissue
or foreign invader cause
neutrophils and macrophages
to move toward source of
chemicals
• Ameboid motion ≡ neutrophils
and macrophages move
through tissue by ameboid
motion by the extension of
pseudopods
http://video.search.yahoo.com/video/play?p=chemo
taxis&ei=UTF-8&fr=yfp-t-
501&tnr=21&vid=0001387379
Important Definitions
• Diapedesis ≡ wbc’s
(neutrophils and
macrophages) squeeze
through very small capillary
pores towards the
chemotactic source
• Opsonization ≡ wbc’s
recognize foreign material
that has been tagged by an
Ab and the C3b product of
the complement cascade
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Important Definitions
• Phagocytosis ≡ the most
important function of
neutrophils and
macrophages is to
recognize, engulf, and
destroy pathogens or
diseased tissue
Neutrophils
• Neutrophils are among the first to arrive at
the site of infection, followed by
macrophages, and then the lymphocytes
• Major role of neutrophils (and macrophages)
is to attack and destroy invading bacteria,
virus, and other toxic agents
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Monocytes & Macrophages
• Monocytes have limited ability to fight infectious
agents except when they enter tissues →
macrophages (become filled with lysosomes and
swell to diameter 5X normal)
• Macrophages are extremely capable of
combating infectious agent through phagocytosis
• Macrophages provide a continuing defense in the
tissue against infection
– Cells can last for years in tissues
Monocyte Macrophage
System
(Reticuloendothelial
System)
• A generalized system present
in all tissues that exhibits
phagocytic properties from
tissue macrophages
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Tissue
Macrophages1. Skin and subcutaneous
tissue
– Histiocytes
2. Lymph nodes
– Trap and destroy invading
organisms
3. Alveoli
– Alveolar macrophages
4. Liver
– Kupffer cells
5. Spleen
– Especially effective at
removing unwanted
organisms and debri from
blood (especially old or
abnormal rbc’s)
Alveolar Macrophage
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Eosinophils
• Weak phagocytes
• Prominent role in protection against parasitic
infection
– Schistosomiasis
– Trichinosis (Trichinella – “pork worm”)
• Elevated in patients with history of allergic
reactions and asthma (atopic individuals)
Basophils
• Participate in allergic reactions
• After their release from the bone marrow,
migrate to respiratory tract, gastrointestinal tract,
and superficial layers of skin
• Behave like mast cells in these locations
– Release histamine, serotonin, bradykinin, heparin,
slow reacting substance of anaphylaxis (SRSA), platelet
activating factor
– ⇒ vasodilation, watery eyes, itching, urticaria, edema
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InflammationDescribes tissue changes
associated with injury
1. Increased blood supply to
the region
2. Increased capillary
permeability → edema
3. Emigration of cells out of
blood vessels into tissues
– Migration of granulocytes
and monocytes and
activation of tissue
macrophages
4. After several days, cavitation
of necrotic tissue, dead
wbc’s = pus
Leukopenia (wbc < 4,000)
• Drugs that depress the bone marrow function– Thiouricil
– Many chemotherapeutic agents
– Phenothiazines
– Radiation
– In general, anesthetic agents depress the immune system, but probably of no clinical significance
• wbc < 2,000 – minor infections
• wbc < 1,000 – serious infections (pneumonia, wound infections)
• wbc < 500 – life-threatening infections
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Leukocytosis (wbc > 10,000)
• White blood cell differential
– “shift to the left” – more immature (band or blast) cells; occurs with acute infection
– “shift to the right” – abnormally large number of mature cells; occurs with chronic infection (e.g. chronic hepatitis)
• Leukocytosis may be caused by infection, steroid ingestion, leukemia, mononucleosis, and nonbacterial tissue injury
Leukemias
• Cancerous mutations of bone marrow (myelogenous) or lymphoid cells (lymphogenous) -produce uncontrolled production of wbc’s and growth of leukemic cells in abnormal parts of the body.
• White blood cells are bizarre and nonfunctional – Patient susceptible to infection
• Rapid metastatic growth of leukemic cells: – other cells starve– tissue destruction– bone pain and fractures– Anemia, thrombocytopenia (displacement of nl bone
marrow with nonfunctional cells)