Transcript Understanding Our Environment - McGraw Hill Higher Education

How The Animal Body Defends Itself
Chapter 25
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Outline
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First Line of Defense
Second Line of Defense
Third Line of Defense
Evolution of Immune System
Initiating Immune Response
T Cell Cellular Response
B Cell Humoral Response
Vaccination
Immune System Failure
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Overview
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Three Lines Of Defense
 Skin - “Walls and Moats”
 Cellular Counterattack - “Roaming Patrols”
 Immune System - “Sentries”
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First Line of Defense
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Skin is largest organ, and provides first line
of defense against microbe invasion.
 Three Layers
- Epidermis
 10-30 cells thick
 Stratum Corneum - outer layer
 Basal Layer - innermost layer
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First Line of Defense
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Dermis
 15-40 times thicker than epidermis.
 Provides structural support for
epidermis.
Subcutaneous Layer
 Composed of fat-rich cells acting as
shock absorbers and insulators.
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Section of Human Skin
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First Line of Defense
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Other External Surfaces
 Digestive Tract
- Saliva
- Acidic Environment
 Respiratory Tract
- Mucosal Layer
- Cilia
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Second Line of Defense
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Four main cellular and chemical defenses:
 Cells that kill invading microbes
 Proteins that kill invading microbes
 Inflammatory response
 Temperature response
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Second Line of Defense
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White Blood Cells That Kill Invading Microbes
 Macrophages - Ingest bacteria.
 Neutrophils - Release chemicals.
 Natural Killer Cells - Attack body cells
infected by invading microbes.
- Puncture membrane
Body’s cells contain self-identifying MHC
proteins.
 Autoimmune Diseases
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Second Line of Defense
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Proteins That Kill Invading Microbes
 Complement System
- Approximately 20 proteins circulate freely
in blood plasma.
 Aggregate to form membrane attack
complex.
 Insert into cell’s plasma membrane
and form pore allowing water to rush
in and burst cell membrane.
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Second Line of Defense
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Inflammatory Response
 Injured cells release chemical alarm signals
(histamine and prostaglandins) that cause
blood vessels to expand.
- Increases blood flow to site of injury.
 Stretches capillary walls increasing
permeability.
 Redness and Swelling
 Phagocyte Migration
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Local Inflammation
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Second Line of Defense
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Temperature Response
 When macrophages initiate counterattack,
they send a message to brain to raise body
temperature.
- Fever inhibits microbial growth.
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Third Line of Defense
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Involve actions of leukocytes
 T and B Cells are lymphocytes.
- T Cells originate in bone marrow and
migrate to thymus.
 Develop ability to identify foreign
particles by antigens exposed on their
surfaces.
 Antigen is any molecule provoking
specific immune response.
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Third Line of Defense
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T Cells
 Inducer - oversee T cell development.
 Helper - initiate immune response.
 Cytotoxic - lyse infected cells.
 Supressor - terminate immune response.
B Cells
 Complete maturation in bone marrow.
- Circulate in blood and lymph.
 Produce antibodies.
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Evolution of Immune System
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Bacteria
 Defend against viral invasion through
restriction endonucleases that degrade
foreign DNA lacking specific DNA pattern.
Invertebrates
 Mark cell surfaces with self labels.
- Employ negative test.
 May not recognize cells that resemble
self marker as foreign.
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Evolution of Immune System
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Shared Elements of Invertebrate and
Vertebrate Immune Responses
 Phagocytes
 Distinguishing Self from Non-Self
 Lymphocytes
 Antibodies
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Evolution of Immune System
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Vertebrates
 Modern vertebrate immune system first
arose in fish with jaws.
- Sharks are oldest surviving group.
 Have immune response much like that
in mammals.
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Copyright © McGraw-Hill Companies
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Initiating Immune Response
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Macrophages inspect surfaces of cells
encountered for MHC proteins.
 T cells only bind to antigens presented to
them on surface of cells.
- Foreign particles are taken in and
partially digested.
 Viral antigens are processed and
moved to the surface of plasma
membrane.
 Antigen Presenting Cells
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Initiating Immune Response
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Macrophages that encounter pathogens
lacking proper MHC proteins, or a virusinfected cell with viral proteins stuck to
surface, secrete alarm signal.
 Interleukin-1
- Stimulates helper T cells to initiate:
 Cellular response of T cells
 Humoral response of B cells
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T Cells: Cellular Response
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Helper T cells become activated when they
bind to complex of MHC proteins and antigens
presented by macrophages.
 Helper T cells secrete interleukin-2.
- Stimulates production of cytotoxic T cells.
 Any cytotoxic T cell whose receptor fits
the particular antigen-MHC protein
complex begins to multiply rapidly.
 Any cells bearing traces of viral
infection are destroyed.
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T Cell Immune Defense
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
B Cells: Humoral Response
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Recognize invading microbes and mark
pathogen for destruction by mechanisms with
no “ID check” system of their own.
 Can bind to free, unprocessed antigens.
 Antigen particles enter B cells by
endocytosis and get processed.
- Helper T cells that recognize the specific
antigen bind to the complex and
stimulate B cells to divide.
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B Cells: Humoral Response
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Antibodies are proteins in class
immunoglobulins (Ig)which is subdivided into
subclasses based on structure and function.
 IgM - Secreted during primary response.
 IgG - Secreted during secondary response.
 IgD - Receptors for antigens on B cells.
 IgA - Found in external secretions.
 IgF - Promotes histamine release.
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B Cell Immune Defense
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B Cells: Humoral Response
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Plasma cells produce large amounts of
particular antibody able to bind to antigen in
initial immune response.
 Memory B cells circulate through lymph
and blood waiting for future encounters.
Antibody Diversity
 When antibody is assembled, different
DNA sequences are brought together to
form composite gene (somatic
rearrangement).
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Active Immunity Through Clonal Selection
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Binding of antigen to its receptor on the
lymphocyte surface stimulates cell division
and produces a clone (clonal selection).
 Primary Immune Response
Next time body is invaded by same pathogen,
there is a large clone of lymphocytes that can
recognize the pathogen.
 Secondary Immune Response
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The Immune Response
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Vaccination
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Introduction into the body of a disabled
pathogen, or a harmless microbe with
pathogen proteins displayed on the surface.
 Triggers immune response without
occurrence of infection.
- Produces circulating memory B cells.
 May not provide effective future
defense if the virus evolves and
surface proteins are altered.
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Immune System Failure
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Autoimmune Diseases
 Killer T cells and B cells lose ability to
distinguish between self and non-self cells.
- Body attacks own tissue.
 Multiple Sclerosis
 Type I Diabetes
 Rheumatoid Arthritis
 Lupus
 Graves Disease
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Immune System Failure
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Allergies
 Body mounts immune response against
harmless substance.
- Mast cells initiate inflammatory response.
 Release histamine causing capillaries
to swell.
 Asthma - Histamine causes narrowing of air
passages in lungs.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
AIDS
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Acquired Immunodeficiency Syndrome first
recognized in 1981.
 Worldwide, 36.1 million have become
infected, and 21.8 million have died.
 Virus recognizes, attacks, and cripples
CD4 T cells.
- With no defense against infection, any of
a variety of otherwise commonplace
infections prove fatal.
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Review
•
•
•
•
•
•
•
•
•
First Line of Defense
Second Line of Defense
Third Line of Defense
Evolution of Immune System
Initiating Immune Response
T Cell Cellular Response
B Cell Humoral Response
Vaccination
Immune System Failure
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies