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TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Chapter 17
Specific Defenses of the Host:
The Immune Response
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
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Differentiate between innate
and acquired immunity.
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Differentiate between immunity and nonspecific resistance.
Specific Defenses of the Host:
The Immune Response
• Innate (nonspecific)
• Immunity
• Antigen (Ag)
• Antibody (Ab)
Defenses against any pathogen,
genetically predetermined
resistance (gender, age, nutrition)
Specific antibody and lymphocyte
response to an antigen
(counteract infection)
A substances that causes the
body to produce specific
antibodies or sensitized T cells
Proteins made in response to an
antigen
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Terminology
• Acquired immunity
• Naturally acquired
active immunity
Resistance to infection during
life of host
Resulting from infection, may be
long-lasting
• Serology
Study of reactions between
antibodies and antigens
• Antiserum
Generic term for serum because
it contains Ab
• Globulins
Serum proteins
• Gamma () globulin
Serum fraction containing Ab
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Serum Proteins – separation by gel electrophoresis
• Immune serum globulin
or gamma globulin
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Figure 17.2
The Immune Response
Differentiate between humoral (antibody-mediated) and cell-mediated immunity.
• Acquired immunity
(vaccination)
Developed during an
individual's lifetime
• Humoral immunity
(in body fluids)
Involves Ab (antibodies)
produced by B cells
• Defend against bacteria, viruses, toxins in blood
plasma and lymph
• Cell-mediated immunity
Involves T cells (certain
lymphocytes)
• Response to intracellular bacteria, viruses, parasites,
transplanted tissue, cancer cells
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Acquired Immunity
Contrast the four types of acquired immunity.
• Naturally acquired active immunity
• Resulting from infection
• Naturally acquired passive immunity
• Transplacental or via colostrum
• Artificially acquired active immunity
• Injection of Ag (antigen - vaccination)
• Artificially acquired passive immunity
• Injection of Ab (antibody) or antiserum
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Antigenic Determinants (epitopes)
• Antibodies recognize and react with antigenic determinants or
epitopes (specific regions on surface of antigen).
• Antigens cause body to produce specific antibodies. Are
components of invading microbes generally.
Define antigen and hapten.
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Figure 17.3
Haptens
• Hapten is a molecule too small to stimulate antibody
formation by itself, until combined with larger carrier
molecule like a serum protein, becoming an antigen.
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Figure 17.4
Antibody Structure (Immunoglobulin) – protein produced
by B cells in response to antigen
Explain the function of antibodies and describe their structural and
chemical characteristics.
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Figure 17.5a-c
IgG antibodies
Name one function for each of the five classes of antibodies.
• Monomer (single bivalent
antibody unit)
• 80% of serum antibodies
• Fix complement
• In blood, lymph, intestine
• Cross placenta
• Enhance phagocytosis;
neutralize toxins & viruses;
protects fetus & newborn
• Half-life = 23 days
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IgM antibodies
• Pentamer (5 monomers)
• 5-10% of serum
antibodies
• Fix complement
• In blood, lymph, on B
cells
• Agglutinates microbes;
first Ab produced in
response to infection
• Half-life = 5 days
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IgA antibodies
• Dimer
• 10-15% of serum
antibodies
• In secretions
• Mucosal protection
• Half-life = 6 days
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IgD antibodies
• Monomer
• 0.2% of serum antibodies
• In blood, lymph, on B cells
• On B cells, initiate immune
response
• Half-life = 3 days
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IgE antibodies
• Monomer
• 0.002% of serum
antibodies
• On mast cells and
basophils, in blood
• Allergic reactions; lysis of
parasitic worms
• Half-life = 2 days
• Involved in allergic
reactions
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Clonal Selection
Name the function of B cells.
• Humoral (fluid) immunity involves antibodies produced
by B cells
• Bone marrow gives rise to B cells.
• Mature B cells migrate to lymphoid organs.
• A mature B cells recognizes epitopes (antigen
receptor).
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•
Differentiation of
T cells and B
cells, both from
stem cells in
adult red bone
marrow or fetal
liver
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Define apoptosis, and give a potential medical application.
•Apoptosis –
normal B cell
below, B cell above
undergoing
apoptosis (bubblelike blebs)
•Programmed cell
death to prevent
overpopulation of B
cells
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Clonal Selection & Differentiation of B cells
•Each particular
B cell recognizes
only one type of
antigen,
activating the B
cell
•Produces clone
of plasma cells
(antibodies) and
memory cells
Describe the clonal selection theory.
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Figure 17.8
Self-tolerance
Explain how an antibody reacts with an antigen; identify the
consequences of the reaction.
• Antigen-antibody complex can result in agglutination,
inflammation, lysis
• Body doesn't make Ab against self
• Clonal deletion
• The process of destroying B and T cells that react to
self antigens
• Amount of antibody in serum called antibody titer
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Protective Mechanism of Ag-Ab Binding
•Result of antigenantibody binding
•Tags foreign cells
and molecules for
destruction by
phagocytes and
complement
(serum proteins for
phagocytosis and
lysis of cells)
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Figure 17.9
Primary and secondary immune response to antigen
• IgM appears
first (primary
response)
Distinguish a primary from a secondary immune response.
• IgG follows
and provides
longer-term
immunity
(high
antibody titer)
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Figure 17.10
Monoclonal Antibodies
Define monoclonal antibodies and identify their advantage over
conventional antibody production.
• Hybridomas are produced by fusing a cancer cell with
an Ab-secreting plasma cells
• The hybridoma cell culture is immortal and produces
monoclonal Abs (Mabs) – serologic identification tests,
prevent tissue rejections
• Immunotoxins: Mabs conjugated with a toxin to target
cancer cells
• Chimeric Mabs: Genetically modified mice that produce
Ab with a human constant region
• Humanized Mabs: Mabs that are mostly human, except
for mouse antigen-binding
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Monoclonal
Antibodies
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Immune system cells communicate via cytokines
Identify at least one function of each of the following in cellmediated immunity: cytokines, interleukins, interferons.
• Interleukin-1
Stimulates TH cells
• Interleukin-2
Activates TH, B, TC, and NK cells
• Interleukin-12
Differentiation of CD4 cells
• -Interferon
Increase activity of macrophages
• Chemokines
Cause leukocytes to move to an
infection
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Chemical messengers: Cytokines
• Cells of immune system communicate via cytokines
• Interleukins (IL) are cytokines between leukocytes
• Interferons protect cells against viruses
• Chemokines cause leukocytes to move to infection site
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Cell-Mediated Immunity
• Specialized lymphocytes, mostly T cells, respond to
intracellular Ags
• After differentiating in the thymus, T cells migrate to
lymphoid tissue
• T cells differentiate into effector T cells when
stimulated by an Ag
• Some effector T cells become memory cells
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Pathogens entering the gastrointestinal or
respiratory tracts pass through:
• M (microfold) cells in
• Peyer's patches which contains
• Dendritic cells which are antigen-presenting cells
and
• T cells
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Dendritic cells present antigens
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Figure 17.12
T Cells
Describe at least one function for each of the following: TH1 cell, TH2 cell, TC
cell, TD cell, TS cell, APC, MHC,activated macrophage, NK cell.
• Helper T Cells (CD4, TH)
• T H1
Activate cells related to cell-mediated
immunity
• T H2
Activate B cells to produce eosinophils, IgM,
and IgE
• Cytotoxic T Cells (CD8, TC)
• Destroy target cells with perforin
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T Cells
• Delayed Hypersensitivity T Cells (TD)
• Associated with allergic reaction, transplant
rejection, and tuberculin skin test
• Suppressor T cells (TS)
• Turn off immune response when Ag no longer
present
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Helper T Cells
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Figure 17.13
Cell-mediated Cytotoxicity
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Figure 17.14
Nonspecific Cells – Activated Macrophages
• Activated
macrophages:
Macrophages
stimulated by
ingesting Ag or by
cytokines
• Natural killer cells:
Lymphocytes that
destroy virusinfected cells,
tumor
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Figure 17.15
T-independent Antigens
•T-indep.
antigen
has
repeating
units that
cross-link
several
antigen
receptors
on same
B cell
B cell
Compare and contrast T-dependent antigens and T-independent antigens.
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Describe the role of
antibodies and NK cells in
antibody-dependent cellmediated cytotoxicity.
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T-independent
Antigens
•How helper T
cells may
activate B cells
to make
antibodies
against Tdependent
antigens
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Figure 17.16
Antibody-Dependent Cell-Mediated Cytotoxicity
Compare and contrast cell-mediated and humoral immunity.
•Eosinophils adhering
to larval stage of
parasitic fluke
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Figure 17.18
Duality of immune system
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