The Immune System

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Chapter 43 The Immune System
Lets Review!
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How many lines of defense do we have against
pathogens?
Three
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The first two lines of defense are considered
nonspecific lines of defense. What does this
mean?
These are nonspecific, meaning that they do not
distinguish one infectious agent from another.
These two lines of defense try to keep out all
pathogens, no matter what they are.
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The third line of defense is a very specific
line of defense. What does this mean?
The components of this line of defense are very
specific in what they will attack.
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The first line of defense is an external
defense. What does this mean?
This line of defense consists of parts of the
body that try to keep the pathogen from ever
entering the body.
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What is a pathogen?
A pathogen is any disease-causing agent.
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List the components of the first line of defense.
Skin Mucous membranes Tears of the eyes Wax in
the ears The HCl acid of the stomach Saliva in
the mouth Secretions of the sweat glands
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The second line of defense is considered an
internal defense. What does this mean?
The second line of defense attacks the pathogen
when the pathogen gets by the first line of
defense and enters the body.
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List the components of the second line of defense.
Phagocytic white blood cells Antimicrobial
proteins The inflammatory response
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List the components of the third line of defense.
Lymphocytes Antibodies
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The secretions of the first line of defense
(tears, wax, saliva) contain what enzyme? What
does this enzyme do?
The enzyme is called lysozyme. It digests the
cell walls of many bacteria and destroys the
bacteria that might enter through the respiratory
system or the openings around the eyes.
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What are phagocytic cells?
Phagocytic Cells Ameba like white blood cells
(leukocytes) that engulf bacteria and digest them
with enzymes. They can leave the bloodstream and
migrate to the site of infection.
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Label the following structures
Microbes
pseudopodia
Vacuole
lysosome
Vacuole and lysosome fuse
Phagocytic Cell (White Blood Cell)
Microbes destroyed by enzymes
Debris released by exocytosis
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What are the three parts to the inflammatory
response?
Fever The white blood cells release chemical
agents which travel to the brain and cause the
temp to rise. The higher temp retards the growth
of bacteria. Redness Caused by the increased
flow of blood to an infected area to promote
healing. Swelling Caused by the increased
amounts of blood to the area.
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List four types of phagocytic cells
Neutrophils Macrophages Eosinophils Natural
killer cells
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60-70 of all leukocytes are of what type?
Neutrophils
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What do neutrophils do?
Neutrophils engulf and destroy microbes.
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List facts about the macrophages
They constitute only 5 of all leukocytes. They
are the largest of the phagocytic cells. They are
the most effective of the phagocytic cells. They
are the longest living of the leukocytes.
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What do the eosinophils do?
They attack multicellular invaders such as
parasitic worms. They position themselves against
the parasites body and then discharge
destructive enzymes that damage the invader.
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What do the natural killer cells do?
These do not attack microorganisms. They destroy
diseased body cells. The NK cells attach to
stricken cells and release chemicals that cause
the stricken cell to lyse. This prevents the
further spread of the virus.
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What brings on the inflammatory response?
The inflammatory response is a set of changes
brought about by signaling molecules released
upon injury or infection. One signaling molecule
is histamine which is stored in mast cells.
Histamine is released by mast cells at sites of
tissue damage. It triggers nearby blood vessels
to dilate and become more permeable.
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microbes
macrophage
Mast cell
Interstitial fluid
Signaling molecules
capillary
RBC
Capillary dilates and become more permeable.
Phagocytes destroy pathogens
Phagocytic cell
Label and explain this process.
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What is the complement system?
Antimicrobial agents include a set of about 30
plasma (blood) proteins known as the complement
system, that carry out a cascade of steps leading
to the lysis of microbes.
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What is the complement system?
Antimicrobial agents include a set of about 30
plasma (blood) proteins known as the complement
system, that carry out a cascade of steps leading
to the lysis of microbes.
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What are interferons?
Interferons are proteins secreted by
virus-infected cells.
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What is the role of the interferons?
Interferons do not benefit the infected cell.
They diffuse to surrounding cells and stimulate
those cells to produce other chemicals that
inhibit viral reproduction. This helps to
control the cell-to-cell spread of viruses.
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What are antigen?
Antigens are foreign molecules that elicit a
specific response by the lymphocytes. The word
antigen is a contraction of "antibody-generator"
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What types of molecules are antigens?
Molecules belonging to Viruses Bacteria Fungi Pro
tozoa Parasitic worms Pollen
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What are the two type of immunity?
Acquired immunity Innate immunity
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What is acquired immunity?
In acquired immunity, our immune system has to
learn how to make antibodies in response to an
infection.
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What is innate immunity?
Innate immunity is the immunity we are born
with. The first two lines of defense are innate
immunity.
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How does the immune response differ from the
other body defenses?
It is very highly specific for the microorganism.
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What type of cell is primarily responsible for
the immune response?
Lymphocytes a type of white blood cell
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What are the two types of lymphocytes?
B-Lymphocytes T-Lymphocytes
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What are the two types of lymphocytes?
B-Lymphocytes T-Lymphocytes
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Where do the lymphocytes originate?
They are formed from stem cells in the bone
marrow.
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What are cytokines?
The phagocytic white blood cells secrete
cytokines. These are proteins that help to
recruit and activate the lymphocytes.
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The immune system consists of what parts of the
body?
Lymph vessels Lymph nodes The thymus
gland Spleen Tonsils White blood cells
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What is the role of the lymph vessels and lymph
nodes?
Microorganisms entering a tissue are swept away
by tissue fluid through the lymph vessels and
trapped in the lymph nodes. A lymph node is a
mass of tissue. They are found throughout the
body, but especially in the neck, armpits, and
groin. Lymph nodes serve as filters, removing
microbes, foreign particles, and dead cells from
circulation. The lymph nodes are filled with
lymphocytes which attack the microorganisms as
they are filtered from the tissue fluid.
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What is the role of the spleen and tonsils?
The spleen and tonsils also filter out
microorganisms and are also rich in lymphocytes.
The lymph nodes filter the lymph fluid or tissue
fluid. The spleen filters the blood, and the
tonsils trap airborne particles.
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What makes the lymphocyte so highly specific for
the type of pathogen it attacks?
Each B cell or T cell has receptor proteins found
on its surface that can bind to a particular
foreign molecule. The receptor proteins on a
single lymphocyte are all the same. A lymphocyte
can bind to only one specific foreign molecule.
There must be a lock and key fit between the
lymphocyte and the foreign antigen. This makes
the lymphocyte highly specific it is
ineffective against any other antigen.
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What makes one lymphocyte different from another?
Lymphocytes differ in the protein receptors found
on the surface of the cell membrane. These
protein receptors will bind to only one specific
pathogen.
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What is an antigen!
Antigen Any foreign molecule that is recognized
by lymphocytes and elicits a response from them.
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How do the B-cells and the T-cells recognize an
antigen?
The B-cells and the T-cells have specific protein
receptors on the cell membrane which matches the
shape of the antigen.
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B-cells give rise to plasma cells that secrete
_____?
Antibodies or immunoglobulins
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100,000 Protein receptors per cell
Protein receptors
All receptors are identical, making the
lymphocyte specialized for just one pathogen
B-cell
B-Cells
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Antigen binding site
Antigen binding site
C Constant V Variable
V
Disulfide bridge
V
V
V
Light chain
C
C
Heavy chain
C
C
Cell membrane
Transmembrane region
Cytoplasm of B-cell
B-Cells
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Each B-cell contains protein receptors that are
Y-shaped and consist of _____.
4 polypeptide chains
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Describe the four polypeptide chains composing
the receptor sites on B-cells.
There are two heavy chains and two light
chains. The chains are held together at several
locations by disulfide bridges.
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What are the constant regions and the
variable regions of the receptors?
In the constant regions, the amino acid sequences
vary little among the receptors present on
different B-cells. In the variable regions, the
amino acid sequence varies extensively from one B
cell to another.
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What forms the binding for the antigen?
The binding site is formed by part of the
variable region of the heavy chain and the
variable region of the light chain.
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What are antibodies?
Antibodies have the same structure and
organization as the B cell receptors except that
they are not membrane bound. They are secreted
and are not attached to a B cell surface.
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Antigen binding site
V
V
C
C
Disulfide bridge
ß chain
a chain
T-cell
cytoplasm
T-Cells
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Describe the polypeptides of a T-cell.
The protein receptors have two polypeptides, and
alpha (a) chain and a beta (ß) chain. They are
help together by disulfide bridges. The two
polypeptides are parallel and do not form a
Y-shape.
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Three different antibodies bind to different
epitopes on the antigen.
Antibody C
Antibody A
epitopes
Antibody B
antibody
antigen
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What is an epitope?
Epitope The region on the antigen that is
recognizable by lymphocytes and antibodies. An
antigen may have several different epitopes,
requiring several different antibodies to render
it ineffective.
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When a B lymphocyte meets a pathogen in the body,
it immediately divides to form what two cells?
A plasma cell and a memory cell
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Plasma cells produce ______.
antibodies
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A plasma cell can produce _____ per cell per
second, but it takes ____ days for the plasma
cell to mature.
30,000 antibodies 5 days
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What do the memory cells do?
Memory cells also produce antibodies.
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What is the difference between plasma cells and
memory cells?
Plasma cells last only until the infection is
over, but memory cells can last a lifetime.
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What happens the first time your immune system
encounters a new pathogen?
The immune system has to learn how to build
B-cells and antibodies that have protein
receptors that match the shape of the antigen.
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What happens the second time your immune system
encounters a new pathogen?
The second time the same pathogen enters the
body, it is immediately recognized, and the
memory cell begins the large-scale production of
the antibody effective against that pathogen.
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The rapid response by the memory cell is called
____.
immunity
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Describe the primary immune response.
This is the first exposure to the pathogen. It
peaks at 10 to 17 days after exposure.
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Describe the secondary immune response.
This is the second exposure to the pathogen. It
peaks at 2 to 7 days after exposure. This
response is faster, or greater magnitude, and
lasts longer.
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In what three ways do antibodies act against
invaders?
They may coat the foreign particle so that it can
be taken away by phagocytic cells. They may
combine with it in such a way that they interfere
with one of the vital processes of the pathogen.
For example preventing the virus from attaching
to the host cell. They may actually lyse the
pathogen. Lysis is the rupturing of the cell
membrane.
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What are the two types of responses the immune
system can make to an antigen?
Humoral Immunity Cell Mediated Immunity
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Describe humoral immunity.
Humoral Immunity involves B cell activation and
results from the production of antibodies that
circulate in the blood plasma and lymph. The
circulating antibodies of the humoral response
defend mainly against free bacteria, toxins, and
viruses present in body fluids.
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Describe cell mediated immunity.
Cell mediated immunity depends on the action of T
cells. These are active against viruses and
bacteria within infected body cells and against
fungi, protozoa and parasitic worms.
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What is active immunity?
Active immunity is obtained by recovering from an
infectious disease.
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How might active immunity be obtained without
getting the disease??
You an acquire active immunity by having a
vaccination.
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What are vaccines?
Vaccines include inactivated bacterial toxins,
killed microbes, parts of microbes, or weakened
microbes. These agents can no longer cause
disease but they retain the ability to act as
antigens, stimulating the immune response.
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What is passive immunity?
Passive immunity may include antibodies being
transferred between baby and mother or by taking
antibiotics.
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How long does passive immunity last?
Passive immunity lasts only a short time. The
immune system never learns to make the antibody
on its own, so this is short term immunity.
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What determines a persons blood type?
Blood types are due to differences in the
antigens on the surface of the red blood cells.
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Blood type Antigen Antibodies Can get blood from Can give blood to




A
A
anti-B
A or O
A or AB
anti-A
B
B
B or O
B or AB
AB
A and B
none
A, B, AB, O
AB
anti-A anti-B
O
none
O
A, B, AB, O