Immune Response
Vocabulary
• Immunology- the study of host defense mechanisms
• Immunity- ability of the host to protect itself against
foreign organisms. Resistance to disease.
• Antigen (Ag)- is a foreign substance that can elicit specific
immune response (IR) when is immunogenic
• Antibody (Ab)- protein produced by the body’s immune
system when it detects harmful substances called antigens
• White blood cells (leukocytes)- chief function is to protect
the body against microorganisms causing disease and fight
infection when it occurs. They are bigger than red blood
cells.
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Leukocytes (White Blood Cells (WBC))
•
Protect the body against microorganisms,
toxins, & tumor cells.
•
•
•
remove dead cells & debris from body
Complete cells with all organelles
Stained & further identified by
•
•
•
•
size
shape of the nucleus
presence/absence of granules
colors taken up by their granules
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• Normal
Blood
Smear
– WBCs
account
for less
than 1%
of
blood’s
volume
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White Blood Cells (WBC)
• 5 Major types of WBC
– Neutrophils
– Eosonophils
– Basophils
– Lymphocytes (T and B Cells)
– Monocytes
• Divided into two categories
– Granuolocytes and Agranuolocytes
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Granuolocytes
• Neutrophils
– are the most common WBC in peripheral blood.
– Circulate in blood 7-10 hrs before migrating into tissue
• Live only a few days (1-2 in tissue)
– “front line of innate defense”
• 1st WBCs to show up at an infection site
–
–
–
–
Increase in # used as an indicator of infection
Extravasate in inflammation rxn
Active phagocytes
Fungi
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Granuolocytes
• Eosinophils
– Defend the body in parasitic infections
• Tapeworms, hookworms, pinworms
– Function in phagocytosis
– Account for less than 5% of WBC
– Involved in allergies
• Reduce or control inflammatory response by destroying
histamine
– Red bi-lobed nucleus with red granules
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Granuolocytes
• Basophils
– Least common WBC in blood
– Non phagocytic
– Smallest but loudest
• Function as “sirens” for inflammation and allergy
– Produce histamine (a vasodilator) and heparin (blood thinner)
– Large, histamine containing granules that stain dark purple to
blue
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Agranulocytes
• These WBC’s lack visible cytoplasmic granules
• Lymphocytes
• Monocytes
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Agranuolocytes
• Lymphocytes
– Cornerstone of the immune system
• 2nd most abundant cells
– Smallest of the WBCs
– Help provide a specific response to attack the invading
organisms
– Are formed in lymphatic tissue throughout the body
• Migrate to lymphatic organs to proliferate
– Two types of lymphocytes
• T cells and B cells, which differ in function and the molecules
that are on their surface also differs
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Agranuolocytes
• Lymphocytes
– T cells
• Circulate through the thymus gland and turn into cells
known as thymocytes
– More than 80% of lymphocytes circulating in the body are T
cells
• When exposed to antigens, they rapidly divide and
produce large number of new T cells that are sensitive
to that type of antigen
– Destroy viral infected cells, as well as cancerous cells
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Agranuolocytes
• T cells
Cytotoxic cells
(Tc) 3 main
Helpergroups
T cells
– Divided
into
Suppressor T cells
Sometimes called
“Killer Cells”
Assist “killer cells” in
performing their
activities
Moderate the immune
response by inhibiting
cytotoxic cells and B
cells
They produce
chemical substances
that are essential in
helping the B cells
destroy foreign
substances
Help protect the body
against disease by
increasing response of
other immune cells
Prevent
autoimmunity- control
overproduction of
both T and B cells
Physically attack
foreign cells- infected
and cancerous cells
Stimulate production
of T and B cells
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Agranuolocytes
• Lymphocytes
– B cells
• Circulate in the blood in an
immature way
• About 10% that circulate the blood
are B cells
• Produce proteins known as
antibodies
– Antibodies attach to foreign
pathogens in the body known as
antigens that are found on the
surface of certain microorganisms
– When B cells divide they produce
an identical copies of antibodies on
their surface
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Agranuolocytes
• Monocytes
– Largest WBC found in the blood
– Play important role in the inflammatory response
– Leave the blood stream (after 2-3 days) to become
macrophages
• As a monocyte or macrophage, these cells are phagocytic
(engulfing) and defend the body against viruses and bacteria
• Present pieces of pathogens to T cells so that pathogens may
be recognized and killed
– Increase in chronic infections
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Macrophages
• Arise from monocytes in bone marrow
• Engulf foreign matter and present antigens on
surfaces where they are recognized by
immunocompetent T cells - macrophages then
termed antigen presenting cells or APCs
• Also secrete soluble proteins that activate T
cells which in turn release chemicals to
activate more macrophages.
Dendritic Cells
• Are a system of antigen presenting cells that function to initiate several
immune responses such as the rejection of organ transplants, and the
formation of T-dependent antibodies
• Found in many non-lymphoid tissues but can migrate via the afferent
lymph or the blood stream to the T-dependent areas of lymphoid organs
where in the periphery capture and process antigens, express lymphocyte
co-stimulatory molecules, and secrete cytokines to initiate immune
responses
• Tolerize T cells to antigens that are innate to the body (self-antigens),
thereby minimizing autoimmune reactions
• Dendritic cells are present in those tissues that are in contact with the
external environment, such as the skin, and the inner lining of the nose,
lungs, stomach and intestines
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