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Lecture 9: Immunity, Disease, and Vaccines
Objectives:
•Understand how the body fights infections
•Defense strategies
•Components of the defense
•Understand how pathogens fight the
defense
•Understand how a vaccine works
Background Reading: Chapter 35
Three Lines of Defense
Barriers at Body Surfaces
• Physical barriers
• Chemical barriers
• Normal flora
• Disposable surfaces
Nonspecific Responses (Innate Immunity)
• Inflammation
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Fast acting cell types (self vs. non-self)
Cells that remove debris
Proteins: hole plugging, hole making, and cutting tools
Specific Immune Responses (Cellular Immunity)
• B and T cells
• Communication
• Antibodies and perforins
Barriers at Body Surface
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Intact skin and mucous membranes
Lysozyme
Normal bacterial flora
Flushing and Sheading
Three Lines of Defense
Barriers at Body Surfaces
Nonspecific Responses (Innate Immunity)
• Inflammation
–
–
–
Fast acting cell types (self vs. non-self)
Cells that remove debris
Proteins: hole plugging, hole making, and cutting tools
Specific Immune Responses (Cellular Immunity)
Nonspecific Responses
• Lymph nodes trap and kill
pathogens
• Natural killer cells attack a
range of targets
• Inflammation
Inflammation
Fast acting cell types (self vs. non-self)
Cells that remove debris
Proteins: hole plugging, hole making, and cutting tools
Complement System
• Plasma proteins
that take part in
both specific and
nonspecific
response
• Activation of one
triggers cascade of
reactions that
activate others
CASCADE
REACTION
FORMATION OF
ATTACK COMPLEXES
LYSIS OF
TARGET
Acute Inflammation
• Nonspecific response to foreign invasion,
tissue damage, or both
• Destroys invaders, removes debris, and
prepares area for healing
• Characterized by redness, swelling,
warmth, and pain
Inflammation
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Mast cells release histamine
Capillaries dilate and leak
Complement proteins attack bacteria
White cells attack invaders and clean up
Inflammation
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Redness- vessel dilation
Warmth- increased blood flow
Swelling- edema, leaking
Pain- pressure on free nerve endings
Three Lines of Defense
Barriers at Body Surfaces
Nonspecific Responses (Innate Immunity)
Specific Immune Responses (Cellular Immunity)
• B and T cells
• Communication
• Antibodies and perforins
Immune Responses
• Directed against specific invaders
• Carried out by T cells, B cells, and
macrophages
• Communication signals such as
interleukins play a vital role
Definitions: B cells, T Cells, and Macrophage
• B cell
– Covered with antibody (one type)
– Don’t recognize MHC presented antibody,
only free antigens
• T Cell
(Thymus)
– Ignore free antigen
– recognize only antigen presented by MHC
• Macrophage
– Clears particles
– Presents MHC antigens
Definitions
Antibody Structure
• Antibody consists of
four polypeptide
chains
• Certain parts of each
chain are variable;
impart antigen
specificity
variable region
of heavy chain
antigen-binding site
variable
region of
light chain
constant
region of
light chain
antigen-binding site
hinge
region
(flexible)
Definitions
Antigen:
Any substance that stimulates the production
of antibodies
Usually a protein or large molecule
Little 3-D shapes that antibodies can
recognize.
Recognition
Self and Non-self
Recognition
MHC
antigen framents
MHC molecule
antigen-MHC complex
Displaying
non-self
Features of Immune System
• Immunological specificity
– B and T cells zero in on certain kinds of
pathogens; response is pathogen specific
• Immunological memory
– Immune system recognizes and reacts
swiftly to a pathogen it has “seen”
Memory and Effector Cells
• When a B or T cell is stimulated to divide,
it produces more than one cell type
• Memory cells are set aside for future use;
they are the basis for immune memory
• Effector cells engage and destroy the
current threat
Key Component of
Immune Response
Key Component of
Immune Response
• MHC markers
• Antigen-presenting cells
• Helper T cells
• Effector cytoxic T cells
• Natural killer cells
• B cells
Overview of an Immune Response
Key Components of
Immune Response
• MHC markers
• Antigen-presenting
cells
• Helper T cells
• Effector cytoxic T cells
• Natural killer cells
• B cells
Antibody mediated
response
Cell - mediated
response
Antigenpresenting
cell
Naive B cell
Naive helper
T cell
Naive
cytotoxic
T cell
Effector
B cell
Activated
helper T
cell
Effector
cytotoxic T
cell
Lymphocyte Battlegrounds
• Lymph nodes filter antigens from
body fluids
• Macrophages, dendritic cells, B
cell and T cells in nodes and
spleen mount a defense
Antibody-Mediated Response
• Carried out by B cells
• Targets are intracellular pathogens and
toxins
• Antibodies bind to target and mark it for
destruction by phagocytes and
complement
Antibody- Mediated
Response
• Virgin B cell becomes
antigen-presenting B
cell
• Helper T cell binds to
antigen-MHC complex
on the B cell
• Interleukins stimulate B
cell division and
differentiation
• Effector cells secrete
antibodies
Naive
B cell
Antigenpresenting
B cell
Helper
T cell
Interleukins
Effector B cell
secretes
antibodies
Memory B cell
5 Classes of Immunoglobulins
• IgM are secreted first; trigger
complement reactions, agglutination
• IgD function is not understood
• IgG activates complement; can cross
placenta
• IgA associates with mucus-coated
surfaces
• IgE triggers inflammation
Cell-Mediated
Response
One
macrophage
Another
macrophage
• Carried out by T cells
• Stimulated by antigenpresenting
macrophages
• Main target is antigenpresenting body cells
(cells with intracellular
pathogens) or tumor
cells
interleukins
Cytotoxic
T cell
interleukins
Helper T
cell
Infected
body cell
Organ Rejection
• Cytotoxic T cells can contribute to
rejection of transplanted tissue
• They recognize a portion of the donor
cell’s MHC complex as self, view a
portion as foreign
• Treat the combination as an antigenMHC complex and attack donor cells
Allergies
• Immune reaction to a harmless substance
• Genetic predisposition
• IgE responds to antigen by binding to mast
cells and basophils
• These cells secrete the substances that cause
symptoms
Anaphylactic Shock
• A life-threatening allergic reaction
• Caused by the release of histamine by
many mast cells and basophils
• Airways constrict and blood pressure
drops as capillary permeability soars
Autoimmune Disorders
• Immune system makes
antibodies against self
antigens
• Grave’s disease
• Myasthenia gravis
• Rheumatoid arthritis
Bacterial Pathogen
Category A Threats:
• Defined by the CDC as high-priority agents include
organisms that pose a risk to national security
because they:
– Can be easily disseminated or transmitted from
person to person
– Result in high mortality rates and have the
potential for major public health impact
– Might cause public panic and social disruption
– Require special action for public health
preparedness.
Bacillus anthracis
Infection type
Cutaneous
Intestinal
Inhalation
Mortality (untreated)
20%
80-90%
90*-99%
*with treatment
Major Symptoms
• Skin– characteristic sores
• Intestinal– fever, intestinal
discomfort, intestinal
ulceration.
• Inhalation– fever, cough, malaise
(flu-like)
– Sever respiratory
distress, chills, edema
Pathophysiology
Immunization
• Process that promotes immunity
• Active immunization – Antigen-containing material is injected
– Confers long lasting immunity
• Passive – Purified antibody is injected
– Protection is short lived
Immunization
first exposure
to antigen
subsequent exposure
to the same antigen
HIV Picture
All you need to know
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Chapter 35
Table 35.1
Table 35.1 figure 35.5
Figure 35.6
Figure 35.7