White Blood Cells

Question 1

Our bodies are exposed continually to bacteria,

viruses, fungi, and parasites:

Answer 1

– Skin
– Mouth
– respiratory passageways
– the intestinal tract
– lining membranes of the eyes
– urinary tract. 
• Can cause more serious infections if they invade the 
deeper tissues
• Other highly infectious bacteria and viruses

Question 2

What are the agents that combat infection and toxic agents

Answer 2

– Blood leukocytes (white blood cells)

– Tissue cells derived from leukocytes

Question 3

How do the agents that combat infection destroy invading bacteria/viruses?

Answer 3

– Phagocytosis

– Forming antibodies and sensitizing lymphocytes

Question 4

Types of White blood cells?

Answer 4

• Granulocytes
• Monocytes
• Lymphocytes
• Plasma cells (occasionally)

Question 5

Granulocytes include:

Answer 5

• Polymorphonuclear Neutrophils
• Polymorphonuclear Eosinophils
• Polymorphonuclear Basophils
– called polys, because of the multiple 
nuclei

Question 6

The genesis of White blood cells is called?

Answer 6

Leukopoesis

• Formation of the different
blood cells from the stem
cell

• NB: 2 major lineages of
white blood cells:
– Myelocytic
– lymphocytic

Question 7

Where are White blood cells formed?

Answer 7

• Partially in the bone marrow
– granulocytes and monocytes

• Partially in the lymph tissue (lymph glands, spleen, thymus, tonsils)
– Lymphocytes and plasma cells

• Transported to where they are needed
– serious infection and inflammation

Question 8

Life span of Granulocytes

Answer 8

Granulocytes: 4-8 hours circulating; 4-5 days in tissues where needed. Shortened to a few hours in serious infection.

Question 9

Life span of Lymphocytes

Answer 9

• Lymphocytes enter the circulatory system continually (via the lymph). Pass out of the blood after a few hours – back into the tissue
(diapedesis). Repeated. Have a lifespan of weeks to months depending on need.

Question 10

Life span of Monocytes

Answer 10

• Monocytes: 10-20 hours in blood live for months as macrophages on 
the tissues (unless destroyed performing phagocytosis)

Question 11

How do White blood cells move?

Answer 11

• Enter the tissue by diapedesis
• Move through the tissue by ameboid motion (40um /min)
• Attracted to the inflamed tissue by chemotaxis

Question 12

What is diapedesis?

Answer 12

Process where the cell squeezes through the pores of
the blood capillaries.
• But a pore is much smaller that a cell

How does it do this?
• A small portion of the cell slides through the pore at a
time: the portion sliding through is momentarily
constricted to the size of the pore

Question 13

What is Chemotaxis?

Answer 13

When a tissue is inflamed, products are formed
– Bacterial or viral toxins
– Degenerative products from the inflamed tissue
– Reaction products from the complement complex
– Reaction products caused by plasma clotting

Causes a concentration gradient
• Concentration greatest near the source
which directs movement of the WBCs.
• Effective up to 100um away from an
inflamed tissue.
Because all tissues are not >50 um away
from a capillary, is an effective way to
move hordes of white blood cells from the
capillaries to the inflamed area.

Question 14

Neutrophils and Macrophages act similarly how?

Answer 14

-In that they attack and destroy the bacteria via Phagocytosis

Question 15

Phagocytosis

Answer 15

Attaches to the particle
• Projects pseudopodia in all directions around the particle
• Pseudopodia meet one another on the opposite side and
fuse
• Creates a chamber with the particle inside
• The chamber invaginates (turns inside out) and forms a
free-floating phagocyte
• Lysozymes and other cytoplasmic granules dump
digestive (proteolytic) enzymes and bactericidal agents (oxidizing agents, eg hydrogen peroxide) into the vesicle = digests the particle.

Question 16

Neutrophils

Answer 16

• Already mature cells
• Can phagocytize 3 -20 bacteria before it dies.
• Are the most abundant of the white blood cells
- 62% of average adult white blood cell count
*(average adult white blood cell count is 7000 cells per microliter blood)
• Normal neutrophil count is 1500 – 8000 cells per microliter blood
• If count > 8000 – neutrophilia (most likely have an infection)
• If count is < 1500 – neutropenia (underlying disease causing the low production of neutrophils)

Question 17

Neutrophilia

Answer 17

wbc > 8000

Question 18

Neutropenia

Answer 18

wbc < 1500

Question 19

Monocytes/Macrophages

Answer 19

Start out as monocytes
– Have large, eccentrically placed, bean-shaped nucleus
• When monocytes enter tissues
– they increase in size (swell)
– and develop large numbers of granules (lysosomes)
• Macrophages are the mature cells
• Attack and destroy bacteria in the blood.
• Can phagocytize up to 100 bacteria (more than
neutrophils)
• Can also engulf larger particles (unlike neutrophils)
• After digestion, extrudes residual products and can
continue to function (>months [many months]).

Question 20

Where are macrophages found?

Answer 20

• Skin (Histiocytes)
• when the skin is broken and infection begins in subcutaneous tissue the local tissue macrophages divide in situ and can phagocytose the pathogen
• Lymph nodes
• Line the lymph sinuses where foreign particles are trapped
• Lungs (Alveolar macrophages)
• phagocytose particles that are entrapped in the alveoli
• liver (Kupffer cells)
• prevent bacteria from the gastrointestinal tract from entering the general systemic circulation.
• Spleen and bone marrow
• phagocytose organisms that succeed in entering the general circulation
• CNS (Microglia)
• located throughout the brain and spinal cord.

Question 21

Reticuloendothelial system aka

Answer 21

(monocyte-macrophage system)

Question 22

Define Reticuloendothelial system

Answer 22

Some macrophages (mobile cells) become attached to the tissues (monocytes) for months to years until stimulated.

• Break away – become mobile macrophages again.
• Combination of monocytes, mobile macrophages, fixed tissue macrophages and some specialized endothelial cells in the bone marrow spleen and lymph nodes make up the reticuloendothelial system.

Question 23

Inflammation is the role of which cells

Answer 23

Role of Neutrophils and Macrophages

Question 24

Inflammation is caused by?

Answer 24

– bacteria, trauma, chemicals, heat

– Release substances that dramatically change the surrounding uninjured tissue.

Question 25

Inflammation is characterized by? The 5 steps of Inflammation

Answer 25

1. Vasodilation of local blood vessel – causes excess blood flow
2. Increased permeability of the capillaries – causes leakage of large amounts of fluid into the interstitial spaces
3. Clotting of the fluid – caused by excessive amounts of fibrinogen leaking from the capillaries
4. Migration of large numbers of granulocytes and monocytes into the tissue
5. Swelling of the tissue cells.

Question 26

The result of the steps?

Answer 26

• “Walling off”: tissue spaces and lymphatics
blocked by fibrinogen clots. Stops fluid
flowing through the spaces. Delays the
spread of bacteria/toxic products

Question 27

1st line of defense (during 1st hr)

Answer 27

: Rapid enlargement of macrophages at the site of

infection. Attached macrophages become mobile.

Question 28

• 2nd line defense (within a few hrs):

.

Answer 28

large number neutrophils invade the inflamed area. Stick to the capillary walls (margination). Pass from the blood into the tissue spaces (diapedesis).

Migrate towards the injured tissue (chemotaxis). Stored
neutrophils in the bone marrow are mobilized into the circulating blood, cause 4-5X increase in numbers of
neutrophils (neutrophilia)

Question 29

3rd and 4th lines of defense

Answer 29

• 3rd line (several days): monocytes from the blood
enter the inflamed tissue and enlarge to macrophages (8hrs). Bone marrow increases production of new monocytes.

• 4th line (3-4 days): increased production (20-50X)
granulocytes and monocytes by bone marrow via
progenitor pathway. Can continue production for
months – yrs.

Question 30

Basophils

Answer 30

• Found in the circulating blood. Similar to tissue mast
cells found immediately outside of the capillaries.
• Release heparin into the blood (prevents clotting).
Also histamine, bradykinin, seratonin (mainly mast
cells)

Question 31

Role of Basophils

Answer 31

Role in allergic reactions because immunoglobulin
E (IgE) attaches to mast cells and basophils.
– When an antigen (Ag) attaches to IgE antibody (Ab), cells rupture.
– Releases large amounts of histamine, bradykinin, serotonin, heparin, slow-reacting substance of anaphylaxis (It induces prolonged, slow contraction of smooth muscle
and has a major bronchoconstriction role in asthma) – allergic manifestation

Question 32

Eosinophils

Answer 32

• Under normal conditions found in the spleen, lymph
nodes and gastrointestinal tract where survive for
several days. Circulate for 8-12 hours
• Usually produced in large numbers in people with
parasitic infections.
– Weak phagocytes
– Instead, attach to the parasites by special surface
molecules and release:
– hydrolytic enzymes from their granules
– Highly reactive forms of oxygen (peroxidases)
– Highly larvicidal polypeptide = major basic protein

Question 33

Role of Eosinophils in detoxification

Answer 33

Also collect in tissues in which allergic reactions
occur (lungs, skin).
– Partly due to release of eosinophil chemotactic factor by
mast cells and basophils
• Detoxify inflammation-inducing substances released
by mast cells and basophils.
• Phagocytose and destroy allergen-antibody
complexes.

Question 34

Lymphocytes

Answer 34

• Large nucleus, little cytoplasm, smallest of WBCs but size
increases when activated by foreign antigen
• Lymphocytes play the central role in all immunological
defence mechanisms, provide specific immune response
(acquired)
• Lymphocytes produced in bone marrow but may undergo
further development and division elsewhere (e.g. thymus –
Tcells; liver – Bcells (from bursa of Fabricius).
• They migrate to lymphoid tissue (mostly lymph nodes,
spleen, tonsils, lymphoid follicles in gastrointestinal tract)
encounter foreign antigen

Question 35

Lymphocyte clones

Answer 35

• Occurs when specific antigens come into contact with the lymphocytes
• Lymphocytes are activated
• B lymphocytes produce antibodies when activated
• T lymphocytes produce activate T cells (can destroy infected cells).
• Activated lymphocytes react highly specifically against the antigens that
initiated their development.
• Produces tremendous amounts of duplicate lymphocytes = clones

Question 36

Cell-mediated and Humoral immunity.

Answer 36

Explain the diagram

Question 37

What is Leukopenia and what does it result in?

Answer 37

• When bone marrow produces very few WBCs
• What is the result?
– Allows invasion of bacteria normally present
(symbiotic bacteria) into adjacent tissues.
– Ulcers appear in the mouth and colon, respiratory
infection
– Bacteria invade surrounding tissue and blood
– Without treatment (transfusion; antibiotics) death
in <2weeks.
• Some stem cells, myeloblasts, and hemocytoblasts
are capable of regenerating the bone marrow – may
take weeks to months – therefore need treatment.

Question 38

What is Leukemia?

Answer 38

• Caused by cancerous mutation of myelogenous or lymphogenous
cell.
• Results in increased numbers abnormal WBCs

Question 39

What are the types of Leukemia?

Answer 39

1. Lymphocytic

2. Myelogenous

Question 40

Lymphocytic leukemia

Answer 40

– Cancerous production of lymphoid cells

– Usually begins in lymph node and spreads to other areas of the body

Question 41

Myelogenous leukemia

Answer 41

– Cancerous production of young myelogenous cells in the bone marrow
– Spreads throughout the body so that WBCs produced in extramedullary tissue (outside of the bone marrow) – especially lymph nodes, spleen, liver.

– Occasionally produces partially differentiated cells
(neutrophilic, eosinophilic etc) – chronic, sometimes
developing slowly over 10-20 years.
-Mostly undifferentiated – the more undifferentiated, the more acute – can lead to death within a few months

Question 42

What are the effects of leukemia on the body?

Answer 42

• Metastatic growth of leukemic cells in abnormal
areas,
– Eg leukemic cells from the bone marrow may invade
surrounding bone, causing pain and eventually a tendency for bones to fracture easily.
• Almost all spread to the spleen, lymph nodes, liver
and other vascular organs.
• Development of infection, severe anemia, bleeding
caused by thrombocytopenia (lack of platelets).
• Excessive use of metabolic substrates by the
cancerous cells (eg foodstuffs, amino acids,
vitamins).
• Causes lack of energy, deterioration of normal
protein tissues (amino acids).

Question 43

Platelets aka Thrombocytes

Answer 43

• What are platelets?
– Minute disc 1-4um in diameter.

• How are they formed?
– Formed in the bone marrow from megakaryocytes (extremely large cells).
– Fragment into minute platelets in the bone marrow or soon after entering the blood.
– Megakaryocytes and platelets bind thrombopoietin
– When platelet count is low, there is increased free thrombopoietin which can stimulate megakaryocytes
– When the platelet count is high, there is decreased free thrombopoietin and decreased stimulation of megakaryocytes

• 300000 platelets per microliter blood. Replaced once every 10 days.
• Eliminated from the circulation by the macrophages, especially in the spleen.

Question 44

What are the characteristics of Platelets?

Answer 44

• No nuclei
• Cytoplasm:
1. Have actin and myosin molecules and thrombosthenin which are contractile proteins.
2. Residuals of ER and Golgi apparatus – store large quantities calcium ions
3. Mitochondria and enzyme systems capable of forming ATP and ADP.
4. Enzyme systems that synthesize prostaglandins (local hormones)
–cause vascular and other tissue reactions.
5. Fibrin-stabilizing factor - coagulation
6. Growth factor – help repair damaged vascular walls.
• Cell membrane has:
– Coat of glycoproteins – selectively adheres to injured endothelium
– Phospholipids – activate multiple stages in the blood-clotting process