Transcript Chapter 47 The Body’s Defense Systems Table of Contents Section 1 Nonspecific Defenses Section 2 Specific Defenses: The Immune System Section 3 HIV and AIDS.

Chapter 47
The Body’s Defense Systems
Table of Contents
Section 1 Nonspecific Defenses
Section 2 Specific Defenses: The Immune System
Section 3 HIV and AIDS
Chapter 47
Section 1 Nonspecific Defenses
Objectives
• Summarize Koch’s postulates for identifying a
disease-causing agent.
• Describe how the skin and mucous membranes
protect the body against pathogens.
• Describe the steps of the inflammatory response.
• Analyze the roles of white blood cells in fighting
pathogens.
• Explain the functions of fever and proteins in fighting
pathogens.
Chapter 47
Section 1 Nonspecific Defenses
Identifying Pathogens
• A pathogen is any agent that causes disease and
can be spread to humans through the air, food,
water, or direct contact with an infected animal or
person.
• A disease that is caused by a pathogenic
bacteria, virus, fungi, or protist is called an
infectious disease.
• Koch’s postulates are “rules” for identifying the
particular pathogen that causes a specific
disease.
Chapter 47
Section 1 Nonspecific Defenses
Pathogen
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Chapter 47
Section 1 Nonspecific Defenses
Koch’s Postulates
Chapter 47
Section 1 Nonspecific Defenses
Koch’s Postulates
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Chapter 47
Section 1 Nonspecific Defenses
First Line of Defense: Barriers
• Nonspecific defenses, such as the skin and
mucous membranes, are barriers to potential
pathogens.
– In addition to being a physical barrier to
pathogens, skin also produces sweat, oils, and
waxes, which are toxic to many bacteria.
– A mucous membrane is a layer of epithelial
tissue that covers internal surfaces of the body
and secretes mucus, a sticky fluid that traps
pathogens.
Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity
• If a pathogen gets past the skin and the mucous
membranes, the body triggers the second line of
defense, which is nonspecific immunity.
– Nonspecific immunity works in the same way
against any pathogen.
– Nonspecific immunity includes the
inflammatory response, the temperature
response, and certain proteins.
Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Inflammatory Response
– An inflammatory response is a series of events that
suppress infection and speed recovery.
– When cells are damaged they release chemical
messengers, such as histamine.
• Histamine is a substance that increases blood flow
to the injured area and increases the permeability
of surrounding capillaries.
Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Inflammatory Response, continued
– Fluids and white blood cells called phagocytes
leak through capillary walls to fight any
pathogens that may have entered the body.
• Phagocytes are cells that ingest and
destroy foreign matter, such as
microorganisms.
Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Inflammatory Response, continued
– The most common phagocyte in the body is
called a neutrophil.
• A neutrophil is a large leukocyte that
contains a lobed nucleus and many
cytoplasmic granules.
Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Inflammatory Response, continued
– A macrophage is a white blood cell that
engulfs pathogens and other materials.
– Another type of white blood cell that attacks
pathogen-infected cells is called a natural
killer cell.
Chapter 47
Section 1 Nonspecific Defenses
Inflammatory Response
Chapter 47
Section 1 Nonspecific Defenses
Inflammatory Response
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Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Temperature Response
– When the body begins to fight pathogens, body
temperature may increase. This rise in
temperature is called a fever.
– The body triggers a fever in order to slow
bacterial growth or to promote white blood cell
activity.
– Though a moderate fever can be helpful, high
fevesr can be dangerous.
Chapter 47
Section 1 Nonspecific Defenses
Fever as Nonspecific Defense
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Chapter 47
Section 1 Nonspecific Defenses
Second Line of Defense: Nonspecific
Immunity, continued
• Proteins
– Proteins also provide nonspecific defenses.
• The complement system is a system of proteins that
circulate in the bloodstream and become active when
they encounter certain pathogens.
• Interferon is a protein released by cells infected with
viruses that enables nearby cells to resist viral
infection.
Chapter 47
Section 2 Specific Defense: The
Immune System
Objectives
• Identify and describe the parts of the immune system.
• Explain how the immune system recognizes
pathogens.
• Compare the actions of T cells and B cells in the
immune response.
• Relate vaccination to immunity.
• Distinguish between allergy, asthma, and
autoimmune disease.
Chapter 47
Section 2 Specific Defense: The
Immune System
The Immune System
• The immune system
includes the cells and
tissues that
recognize and attack
foreign substances in
the body.
• The components of
the immune system
are found throughout
the body.
Chapter 47
Section 2 Specific Defense: The
Immune System
The Immune System, continued
• Bone marrow, the thymus, lymph nodes, the
spleen, adenoids, and tonsils are all part of the
immune system.
• Each part of the immune system plays a special
role in defending the body against pathogens.
• The specialized cells of the immune system are
called lymphocytes. Lymphocytes are white
blood cells that exists in two primary forms: T
and B cells.
Chapter 47
Section 2 Specific Defense: The
Immune System
The Immune System, continued
• B cells are white blood cells that are made in the
bone marrow and complete their development
there or in the spleen. B cells make antibodies.
• T cells are cells that are made in the bone marrow
but complete their development only after
traveling to the thymus. T cells also participate in
many immune reactions.
Chapter 47
Section 2 Specific Defense: The
Immune System
Recognizing Pathogens
• Lymphocytes can
provide specific
defenses because they
recognize pathogens by
the antigens on their
surface.
• An antigen is any
substance that the
immune system does
not recognize as part of
the body.
Chapter 47
Section 2 Specific Defense: The
Immune System
Recognizing Pathogens, continued
• Because the lymphocytes
do not recognize the
antigen, they start a
specific attack known as an
immune response.
• Lymphocytes recognize a
pathogen with molecules
on their surface called
receptor proteins.
Chapter 47
Section 2 Specific Defense: The
Immune System
Recognizing Pathogens, continued
• An antigen has a
complementary threedimensional shape that
allows the receptor
protein to bind to it. This
is how the lymphocyte
recognizes the antigen.
• Only the specific receptor
protein that is
complementary to the
antigen will be able to
bind there.
Chapter 47
Section 2 Specific Defense: The
Immune System
How a Cytotoxic T Cell
Recognizes an
Infected Cell
Chapter 47
Section 2 Specific Defense: The
Immune System
Recognition of Pathogens
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Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response
• An immune response is a two-part assault on a
pathogen. Both parts occur at the same time and
require a specialized lymphocyte called a helper T
cell.
• The two parts of the immune response are the cellmediated immune response and the humoral
immune response.
• T cells activate certain proteins that affect the
behavior of other immune cells. These proteins are
called cytokines.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Cell-Mediated Immune Response
– In the cell-mediated immune response,
cytokines activate more helper T cells and
another type of T cell called a cytotoxic T cell.
• Cytotoxic T cells recognize and destroy cells
that have been infected by a pathogen.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Cell-Mediated Immune Response, continued
– Also produced during the cell-mediated
immune response is a type of T cell called the
suppressor T cell.
– Suppressor T cells are thought to shut down
the immune response after the pathogen has
been cleared from the body.
Chapter 47
Section 2 Specific Defense: The
Immune System
Cell-Mediated Immune Response
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Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Humoral Immune Response
– The humoral immune response involves the action
of B cells and occurs when antibodies are
activated within body fluids.
– The humoral immune response occurs at the same
time as the cell-mediated immune response.
– During the humoral response, cytokines stimulate
B cells that have receptors that are
complementary to the antigen to divide and
change.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Humoral Immune Response, continued
– Most B cells form plasma cells. A plasma cell is
a white blood cell that produces antibodies.
– Antibodies are defensive proteins that react to a
specific antigen or inactivate or indirectly
destroy toxins.
– Antibodies use various methods to disable a
pathogen or cause its destruction by
nonspecific responses.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Primary and Secondary Immune Responses
– The first time the body encounters an antigen,
the immune response is called a primary
immune response.
– During this first encounter, the immune system
fights off the disease. After the disease is
overcome, the immune system creates
memory cells.
• Memory cells are a B cell or T cell that will
recognize and attack the antigen or
invading cell during subsequent infections.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immune Response, continued
• Primary and Secondary Immune Responses,
continued
– The second time the body encounters an
antigen, a secondary immune response occurs.
– During a secondary immune response, the
immune response is faster and more powerful.
– Most of the time, the secondary immune
response protects the body from reinfection
by a pathogen.
Chapter 47
Section 2 Specific Defense: The
Immune System
The Immune Response
Chapter 47
Section 2 Specific Defense: The
Immune System
The Immune Response, continued
Chapter 47
Section 2 Specific Defense: The
Immune System
Primary and Secondary Immune Responses
Chapter 47
Section 2 Specific Defense: The
Immune System
Primary and Secondary Immune Response
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Chapter 47
Section 2 Specific Defense: The
Immune System
Immunity and Vaccination
• Immunity is the ability to resist an infectious
disease.
• Immunity can come about in two ways: surviving
an initial infection or through vaccination.
– Vaccination is the introduction of antigens
into the body to cause immunity.
Chapter 47
Section 2 Specific Defense: The
Immune System
Immunity and Vaccination, continued
• Vaccines
– Vaccination usually involves an injection of a
vaccine.
– A vaccine is a solution that contains a dead or
weakened pathogen or material from a pathogen
that still contains antigens.
– The immune system will produce a primary
immune response to the antigens. Memory cells
can then provide a quick secondary immune
response if the antigen ever enters the body
again.
Chapter 47
Section 2 Specific Defense: The
Immune System
Vaccine
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Chapter 47
Section 2 Specific Defense: The
Immune System
Problems of the Immune System
• Sometimes the immune system can react to
harmless antigens. Three examples of this are
allergies, asthma, and autoimmune diseases.
• Allergies
– An allergy is a physical response to an
antigen, which can be a common substance
that produces little or no response in the
general population.
Chapter 47
Section 2 Specific Defense: The
Immune System
Problems of the Immune System
• Asthma
– Allergies can trigger asthma. Asthma is a
respiratory disorder that causes the
bronchioles to narrow due to an overreaction
to substances in the air.
– During an asthma attack, the lining of the
bronchioles and other respiratory tissues may
also swell and become inflamed.
Chapter 47
Section 2 Specific Defense: The
Immune System
Problems of the Immune System
• AIDS (acquired immunodeficiency syndrome) is
a disease caused by HIV (human
immunodeficiency virus).
– Infection by HIV causes the immune system to
lose its ability to fight off pathogens and
cancers.
– HIV infection usually progresses to AIDS in
three phases.
Chapter 47
Section 3 HIV and AIDS
Objectives
• Describe the relationship between HIV and AIDS.
• Distinguish between the three phases of HIV
infection.
• Identify the two main ways that HIV is transmitted.
• Determine how the evolution of HIV affects the
development of vaccines and treatment.
Chapter 47
Section 3 HIV and AIDS
The Course of HIV Infection
• AIDS (acquired immunodeficiency syndrome) is a
disease caused by HIV (human immunodeficiency
virus).
– Infection by HIV causes the immune system to
lose its ability to fight off pathogens and
cancers.
– HIV infection usually progresses to AIDS in
three phases.
Chapter 47
Section 3 HIV and AIDS
The Course of HIV Infection, continued
• Phase I
– Phase I of HIV infection is called the
asymptomatic stage, because there are few or
no symptoms of the disease.
– During this period of the disease the viruses
increase rapidly due to replication.
– Phase I can last up to 10 years or more.
Chapter 47
Section 3 HIV and AIDS
The Course of HIV Infection, continued
• Phase II
– The beginning or worsening of symptoms
marks the start of the second phase of HIV
infection.
– B cells continue making antibodies, but T cells
begin to decline steadily as the virus continues
to replicate.
Chapter 47
Section 3 HIV and AIDS
The Course of HIV Infection, continued
• Phase III
– Phase III of HIV infection is the point where the
number of helper T cells drops so low that they
can no longer stimulate B cells and cytotoxic T
cells to fight invaders.
– AIDS is diagnosed when the helper T-cell
count drops below a certain level.
Chapter 47
Section 3 HIV and AIDS
The Course of HIV Infection, continued
• Phase III, continued
– AIDS is also diagnosed if an opportunistic infection has
developed.
• Opportunistic infections are illnesses caused by
pathogens that produce disease in people with
weakened immune systems. These organisms
usually do not creat problems in people with a
healthy immune system.
– Drug therapy can slow the progress of HIV infection to
AIDS, but there is no cure for AIDS.
Chapter 47
Section 3 HIV and AIDS
Course of HIV Infection
Chapter 47
Section 3 HIV and AIDS
Transmission of HIV
• HIV is transmitted by the transfer of body fluids
containing HIV or HIV-infected cells.
• This most commonly occurs by sexual contact
with an infected person or by use of syringes and
hypodermic needles that have been contaminated
with blood containing HIV.
• HIV cannot be transmitted through casual
contact.
Chapter 47
Section 3 HIV and AIDS
Known Routes of HIV Transmission
Chapter 47
Section 3 HIV and AIDS
Course of an HIV Infection
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Chapter 47
Section 3 HIV and AIDS
Vaccines and Treatments
• Effective treatments and vaccines for HIV are
difficult to create, because HIV has a rapid
evolution rate.
• Treatment is also difficult because HIV quickly
becomes resistant to antiviral drugs.
• Most HIV treatments are expensive and require a
complicated multidrug therapy.
Chapter 47
Section 3 HIV and AIDS
Spread of AIDS
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