Transcript Specific Defenses

Specific Defenses
The Immune System
Definitions
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Innate (nonspecific)
Defenses against any pathogen
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Immunity
Specific antibody and lymphocyte
response to an antigen
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Antigen (Ag)
A substances that causes the
body to produce specific
antibodies or sensitized T cells
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Antibody (Ab)
Proteins made in response to an
antigen
Terminology
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Serology
Study of reactions between
antibodies and antigens
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Antiserum
because
Generic term for serum
it contains Ab
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Globulins
Serum proteins
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Gamma () globulin Serum fraction containing
Ab
Serum Proteins
Figure 17.2
Immunity Types
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Acquired immunity
Developed during an
individual's lifetime
Humoral immunity
by
Involves Ab produced
B cells
Cell-mediated immunity
Involves T cells
Acquired Immunity
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Naturally acquired active immunity
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Naturally acquired passive immunity
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Transplacental or via colostrum
Artificially acquired active immunity
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Resulting from infection
Injection of Ag (vaccination)
Artificially acquired passive immunity
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Injection of Ab
Antigenic Determinants
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Antibodies recognize and react with antigenic
determinants or epitopes.
Figure 17.3
Haptens
Figure 17.4
Antibody Structure
Figure 17.5a-c
IgG antibodies
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Monomer
80% of serum antibodies
Fix complement
In blood, lymph, intestine
Cross placenta
Enhance phagocytosis;
neutralize toxins &
viruses; protects fetus &
newborn
Half-life = 23 days
IgM antibodies
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Pentamer
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
IgE antibodies
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Monomer
0.002% of serum
antibodies
On mast cells and
basophils, in blood
Allergic reactions;
lysis of parasitic
worms
Half-life = 2 days
Clonal Selection
Figure 17.8
Clonal Selection
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Bone marrow gives rise to B cells.
Mature B cells migrate to lymphoid
organs.
A mature B cells recognizes epitopes.
Self-tolerance
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Body doesn't make Ab against self
Clonal deletion
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The process of destroying B and T cells
that react to self antigens
The Results of Ag-Ab
Binding
Figure 17.9
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Antibody titer:
Is the amount of Ab in serum
Figure 17.10
Monoclonal Antibodies
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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)
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
Monoclonal Antibodies
Figure 17.11
Immune system cells
communicate via cytokines
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Interleukin-1
Interleukin-2
NK cells
Interleukin-12
cells
-Interferon
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Chemokines
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Stimulates TH cells
Activates TH, B, TC, and
Differentiation of CD4
Increase activity of
macrophages
Cause leukocytes to move
to an infection
Cell-Mediated Immunity
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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
Pathogens entering the
gastrointestinal or
respiratory tracts pass
through:
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M (microfold) cells in
Peyer's patches which contains
Dendritic cells which are antigenpresenting cells and
T cells
Dendritic cells present antigens
Figure 17.12
T Cells
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Helper T Cells (CD4, TH)
TH1 Activate cells related to cell-mediated
immunity
 TH2
Activate B cells to produce eosinophils,
IgM, and IgE
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Cytotoxic T Cells (CD8, TC)
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Destroy target cells with perforin
Helper T Cells
Figure 17.13
Cell-mediated Cytotoxicity
Figure 17.14
Nonspecific Cells
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Activated
macrophages:
Macrophages
stimulated by
ingesting Ag or by
cytokines
Natural killer
cells: Lymphocytes
that destroy
virus-infected
cells, tumor
Figure 17.15
T-independent Antigens
Figure 17.16
Antibody-Dependent CellMediated Cytotoxicity
Figure 17.18