Download Immune System

Chapter 13
Body Defense
Mechanisms
Suggested Lecture
Presentation
Susan Capasso, Ed.D., CGC
St. Vincent’s College
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Body Defense Mechanisms
 The body’s defense system targets
pathogens and cancerous cells
 The body has three lines of defense
 The immune system distinguishes self
from nonself
 The immune system mounts antibodymediated responses and cell-mediated
responses
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Body Defense Mechanisms
 The cell-mediated immune response and
the antibody-mediated immune response
have the same steps
 Immunity can be active or passive
 Monoclonal antibodies are used in
research, clinical diagnosis, and disease
treatment
 The immune system can cause problems
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The Body’s Defense System
 The body’s defense mechanisms target
pathogens and cancerous cells
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The Body Has 3 Lines of Defense

The body has three lines of defense

Nonspecific
1. Physical and chemical surface barriers
2. Internal cellular and chemical defense
 Specific
3. Immune response
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The Body Has 3 Lines of Defense
Nonspecific defenses
First line of defense:
Nonspecific physical and
chemical surface barriers
Second line of defense:
Nonspecific internal cellular
and chemical defense
If pathogen
penetrates barriers
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Specific defenses
Third line of defense:
Immune response
If pathogen
survives nonspecific
internal defenses
Figure 13.1
Nonspecific Surface Barriers
 Physical and chemical barriers
 The skin
 Nearly impenetrable
 Waterproof
 Resistant to most toxins and enzymes of
invading organisms
 Sweat and oil glands
 Produce chemicals that slow or prevent
the growth of bacteria
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Nonspecific Surface Barriers
 Physical and chemical barriers (continued)
 Mucus of the respiratory and digestive tracts
 Sticky and traps many microbes
 The lining of the stomach
 Produces hydrochloric acid and digesting
enzymes that destroy pathogens
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Nonspecific Surface Barriers
 Physical and chemical barriers (continued)
 Urine
 Slows bacterial growth with acidity
 Washes microbes from urethra
 Saliva and tears
 Contain lysozyme, an enzyme that kills
bacteria
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Nonspecific Surface Barriers
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Figure 13.2 (1 of 2)
Nonspecific Surface Barriers
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Figure 13.2 (2 of 2)
Nonspecific Internal Defenses
 The second line of defense




Defensive cells
Defensive proteins
Inflammation
Fever
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Nonspecific Internal Defenses
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Table 13.1
Nonspecific Internal Defenses
PLAY
Animation—The Inflammatory Response
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Nonspecific Internal Defenses
 Defensive cells include neutrophils and
macrophages
 They engulf pathogens, damaged tissue, or
dead cells by the process of phagocytosis
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Nonspecific Internal Defenses
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Figure 13.3
Nonspecific Internal Defenses
 Eosinophils
 Attack pathogens that are too large for
phagocytosis, such as parasitic worms
 Get close to the parasites and discharge
destructive enzymes that destroy them
 Natural killer (NK) cells
 Search out abnormal cells, including
cancerous cells, and kill them
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Nonspecific Internal Defenses
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Figure 13.4
Nonspecific Internal Defenses
 The body’s non-specific cellular defenses
use two types of defensive proteins
 Interferons
 Complement system
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Nonspecific Internal Defenses
 Before a virally–infected cell dies, it
secretes small proteins called interferons
that
 Attract macrophages and natural killer cells
 Stimulate neighboring cells to make proteins
that prevent the viruses from replicating
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Nonspecific Internal Defenses
 The complement system
 A group of proteins that enhance both
nonspecific and specific defense
mechanisms by
 Destroying pathogens
 Enhancing phagocytosis
 Stimulating the inflammatory response
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Nonspecific Internal Defenses
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Figure 13.5 (1 of 3)
Nonspecific Internal Defenses
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Figure 13.5 (2 of 3)
Nonspecific Internal Defenses
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Figure 13.5 (3 of 3)
Nonspecific Internal Defenses
 Inflammatory response destroys
invaders and helps repair and restore
damaged tissue




Redness
Heat
Swelling
Pain
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Nonspecific Internal Defenses
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Figure 13.6 (1 of 2)
Nonspecific Internal Defenses
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Figure 13.6 (2 of 2)
Nonspecific Internal Defenses
 The increased blood flow to damaged
tissue stimulates mast cells and basophils
to release histamine
 Increases blood flow by dilating blood
vessels and increasing the permeability of
the capillaries
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Nonspecific Internal Defenses
 Fluid leaks from the capillaries
 Causes swelling
 Blood flow increases
 Causes redness and warmth
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Nonspecific Internal Defenses
 Fever
 An abnormally high body temperature
caused by pyrogens
 Chemicals that reset the brain’s
thermostat to a higher temperature
 A moderately higher body temperature
helps fight bacterial infections
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Nonspecific Internal Defenses
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Figure 13.7
Nonspecific Internal Defenses
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Table 13.1
Specific Immune Responses
 The third line of defense is the immune
system
 Has specific responses and memory
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Specific Immune Responses
 Immune response
 The body’s specific defenses
 Work together in the recognition and
destruction of specific pathogens
 Have memory
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The Immune System Distinguishes Self from
Nonself
 The body must be able to distinguish a
foreign organism or molecule from self
 MHC markers are found on our own cells
and mark them as belonging to us
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The Immune System Distinguishes Self from
Nonself
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Figure 13.8
The Immune System
 Antigens
 Nonself substances that trigger an immune
response
 Usually large molecules, such as proteins,
polysaccharides, or nucleic acids
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The Immune System
 When an antigen is detected
 B lymphocytes and T lymphocytes that
recognize the antigen are stimulated to
divide repeatedly
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The Immune System
 Some of these cells attack and eliminate
the invader
 Others are stored in a state of suspended
animation as a form of memory of the
invader
 Available to attack if there is a reoccurrence
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Antibody-Mediated Responses
 Antibody-mediated immune responses
 Defend against antigens that are free in body
fluids, including toxins or extracellular
pathogens
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Antibody-Mediated Responses
 B cells use antibodies to neutralize the
antigen
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Antibody-Mediated Responses
Step 1: Threat
Antigen
Engulfed
Step 2: Detection
Macrophage
Presents antigen to
identify invader and
activates helper T cells
Step 3: Alert
Memory
helper T cell
Helper T cell
Step 7: Continued
surveillance
Cell divides
Cell divides
Antibody-mediated response
Cell-mediated response
Activates
Naive B cell
Step 4: Alarm
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Activates
Effector
helper T cell
Step 4: Alarm
Naive
cytotoxic T cell
Figure 13.9 (1 of 3)
Antibody-Mediated Responses
Antibody-mediated response
Activates
Naive B cell
Step 4: Alarm
Step 5: Building
specific defenses
Effector
helper T cell
Cell divides
Plasma cell
Step 6: Defense
Secretes
Memory B cell
Step 7: Continued
surveillance
Memory cells
remain and provide
a quick response to
the antigen in a
future encounter
Antibodies
Targets
Pathogens or toxins
outside of cells
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Figure 13.9 (2 of 3)
Antibody-Mediated Responses
B cell
Helper T cell
Step 4: Alarm
The helper T cell stimulates
the B cell to begin dividing.
B cell
Step 5: Building
specific defenses
The B cell divides and
forms plasma cells and
memory cells.
B cell
Memory B cell
Plasma cell
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Figure 13.12 (1 of 2)
Antibody-Mediated Responses
Step 5: Building
specific defenses
The B cell divides and
forms plasma cells and
memory cells.
B cell
Memory B cell
Plasma cell
Step 6: Defense
Plasma cells secrete
antibodies specific
for that antigen.
Plasma cell
Antibodies
Step 7: Continued
surveillance
Memory B cells remain and
mount a quick response if
the invader is encountered
again.
Memory B cells
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Figure 13.12 (2 of 2)
Cell-Mediated Responses
 Cell-mediated immune responses
 Involve living cells
 Protect against cellular threats, including
body cells that have become infected and
cancer cells
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Cell-Mediated Responses
Step 1: Threat
Antigen
Engulfed
Step 2: Detection
Macrophage
Presents antigen to
identify invader and
activates helper T cells
Step 3: Alert
Memory
helper T cell
Helper T cell
Step 7: Continued
surveillance
Cell divides
Cell divides
Antibody-mediated response
Cell-mediated response
Activates
Naive B cell
Step 4: Alarm
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Activates
Effector
helper T cell
Step 4: Alarm
Naive
cytotoxic T cell
Figure 13.9 (1 of 3)
Cell-Mediated Responses
Cell-mediated response
Effector
helper T cell
Activates
Step 4: Alarm
Naive
cytotoxic T cell
Step 5: Building
specific defenses
Cell divides
Memory cells
remain and provide
a quick response to
the antigen in a
future encounter
Memory
cytotoxic T cell
Step 7: Continued
surveillance
Effector
cytotoxic T cell
Step 6: Defense
Targets
Cells infected with intracellular
pathogen; cancer cells; cells of
organ transplants
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Figure 13.9 (3 of 3)
Cell-Mediated Responses
Antigen
Virus
Helper T cell
Step 4: Alarm
The helper T cell stimulates a
naive or memory cytotoxic T
cell to begin dividing.
Cytotoxic T cell
Step 5: Building specific
defenses
The cytotoxic T cell divides
and forms effector cytotoxic
T cells and memory
cytotoxic T cells.
Memory
cytotoxic T cell
Effector
cytotoxic T cell
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Figure 13.14 (1 of 2)
Cell-Mediated Responses
Step 5: Building specific
defenses
The cytotoxic T cell divides
and forms effector cytotoxic
T cells and memory
cytotoxic T cells.
Memory
cytotoxic T cell
Effector
cytotoxic T cell
Step 6: Defense
Effector cytotoxic cells
cause the target cell to
burst and die. In this case,
the target cell is a cell
infected with a virus that
triggered the response.
Target cell
Perforin
T cell membrane
Target cell membrane
Perforin assembling
into pores
Step 7: Continued
surveillance
Memory cytotoxic T cells
remain and mount a quick
response if the invader is
encountered again.
Memory cytotoxic T cells
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Figure 13.14 (2 of 2)
Cell-Mediated Responses
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Table 13.2 (1 of 2)
Cell-Mediated Responses
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Table 13.2 (2 of 2)
Cell-Mediated Responses
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Table 13.3 (1 of 2)
Cell-Mediated Responses
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Table 13.3 (2 of 2)
Cell-Mediated Responses
PLAY
Animation—Antibody- and Cell-Mediated Immunity
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Immune Response Steps
1. Threat

Foreign cell or molecule enters the body
2. Detection

Macrophage detects foreign cell or
molecule and engulfs it
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Immune Response Steps
3. Alert


Macrophages present antigens to helper Tcells to trigger an immune response
They are called antigen-presenting cells
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Immune Response Steps
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Figure 13.10
Immune Response Steps
4. Helper T cells activate B cells and T cells
to destroy the specific antigen
 When activated, these cells divide to form
clones of cells designed to eliminate a
specific antigen from the body
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Immune Response Steps
B-cell
receptor
There is a
tremendous
variety of B cells.
Each B cell has
receptors for a
different antigen
on its surface.
B cells
This B cell has
receptors specific
for this particular
antigen.
Antigen
The antigen binds to the
B cell with appropriate
receptors.
The selected B cell
divides, producing a
clone of cells all bearing
receptors specific for
that particular antigen.
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Figure 13.11 (1 of 2)
Immune Response Steps
The selected B cell
divides, producing a
clone of cells all bearing
receptors specific for
that particular antigen.
Plasma cells produce
antibodies specific for
this particular antigen.
Plasma
cells
Memory cells remain
to bring about a quick
response to that
antigen in the future.
Memory cells
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Figure 13.11 (2 of 2)
Immune Response Steps
5. Specific defense mechanism is built
 B cells form plasma cells that secrete
antibodies into the bloodstream that bind to
antigens
 T cells form cytotoxic T cells that attack
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Immune Response Steps
B cell
Helper T cell
Step 4: Alarm
The helper T cell stimulates
the B cell to begin dividing.
B cell
Step 5: Building
specific defenses
The B cell divides and
forms plasma cells and
memory cells.
B cell
Memory B cell
Plasma cell
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Figure 13.12 (1 of 2)
Immune Response Steps
Step 5: Building
specific defenses
The B cell divides and
forms plasma cells and
memory cells.
B cell
Memory B cell
Plasma cell
Step 6: Defense
Plasma cells secrete
antibodies specific
for that antigen.
Plasma cell
Antibodies
Step 7: Continued
surveillance
Memory B cells remain and
mount a quick response if
the invader is encountered
again.
Memory B cells
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Figure 13.12 (2 of 2)
Immune Response Steps
6. Primary defense
 Antibodies specific to the antigen eliminate
the antigen
 Cytotoxic T cells release perforins that
cause cells with the antigen to burst
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Immune Response Steps
 Immunoglobulins
 Five classes of antibodies, each with a
special role to play in protecting against
invaders
 IgG
 IgM
 IgE
 IgA
 IgD
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Immune Response Steps
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Figure 13.13
Immune Response Steps
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Table 13.4
Immune Response Steps
7. Immunological memory
 Allows for a more rapid response on
subsequent exposure to the antigen
 Primary response may be slow as the
antibody concentration rises
 Secondary response is strong and swift
due to the large number of specific
memory cells that can respond to the
antigen
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Immune Response Steps
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Figure 13.15
Immune Response Steps
8. Suppressor T cells
 Turn off the immune response when the
antigens no longer pose a threat
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Active Immunity
 Active immunity
 The body actively participates by producing
memory B cells and T cells following
exposure to an antigen
 This process can also happen through
vaccination
 Because memory cells are produced, active
immunity is relatively long lived
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Passive Immunity
 Passive immunity
 Results when a person receives antibodies
that were produced by another person or
animal
 Short lived since the recipient’s body was not
stimulated to produce memory cells
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Monoclonal Antibodies
 Monoclonal antibodies
 A group of identical antibodies that bind to
one specific antigen
 Used in research, clinical diagnosis, and
disease treatment because they can help
diagnose certain diseases in their early
stages
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The Immune System Can Cause Problems
 Autoimmune disorders
 Failure to recognize distinguish between self
and nonself
 Occur when the immune system attacks the
body’s own cells
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The Immune System Can Cause Problems
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Figure 13.16
Immune System Problems
 Allergies
 Immune responses to harmless substances
called allergens
 Allergens cause plasma cells to release
large numbers of class IgE antibodies
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Immune System Problems
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Figure 13.17
Immune System Problems
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Table 13.6
Immune System Problems
 These IgE class antibodies bind to mast
cells or basophils, causing them to release
histamine
 The histamine causes redness, swelling,
itching, and other symptoms of an allergic
response
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Immune System Problems
First exposure
Step 1: The invader (allergen)
enters the body.
Allergen
Step 2: Plasma cells produce
large amounts of class IgE
antibodies against the
allergen.
Plasma cell
IgE antibody
Step 3: IgE antibodies attach
to mast cells, which are found
in body tissues.
Granules
containing
histamine
Mast cell
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Figure 13.18 (1 of 2)
Immune System Problems
Subsequent (secondary) response
Step 4: More of the same
allergen invades the body.
Step 5: The allergen
combines with IgE attached
to mast cells. Histamine and
other chemicals are released
from mast cell granules.
Antigen
Histamine
Step 6: Histamine causes
blood vessels to widen and
become leaky. Fluid enters
the tissue, causing swelling.
• Histamine stimulates release
of large amounts of mucus.
• Histamine causes smooth
muscle in walls of air tubules
in lungs to contract.
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Figure 13.18 (2 of 2)
Immune System Problems
 Antihistamines are most effective in
reducing the allergy symptoms
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Immune System Problems
 Allergy shots inject increasing amounts of
a known allergen in an effort to desensitize
the person to the offending allergens
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