Disease and the
Immune System
Disease: Any change to
normal body function
except for injury.
 Some diseases are genetic
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PKU
Sickle-cell anemia
Type I Diabetes
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 Materials in the environment often cause
disease.
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Cigarette smoke
Chemicals
Toxins
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Other causes of disease
 Pathogens: The causes of infectious diseases.
 Bacteria, virus, protozoa, fungi, and parasites
 Not ALL species of these organisms are pathogens.
 Reservoir: Source of the pathogen in the
environment.
 Animals, humans, soil, inanimate objects.
 Infectious
disease__________________________________
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Spread of infectious
diseases
 Physical contact
 Touch, sexual or indirect contact
 Contaminated food/water
 Infected animals
 Vectors
Vectors: Organisms that
carry the disease
 Most common are ticks and mosquitoes
through biting.
 Flies can act as a vector by landing in
disease and then on humans.
Symptoms of disease
 When a pathogen invades it infects cells of the
body.
 These infected cells are often ruptured, or killed.
 Other times toxins are produced that affect specific
organs or systems.
Sometimes the
symptoms felt are
the body’s immune
system fighting
back.
Disease Patterns
 As an outbreak of a disease spreads a
number of agencies are notified.
 CDC and WHO monitor disease patterns
 Endemic disease
 Epidemic
 Pandemic
Methods of fighting
disease
 The Immune System – natural
defense
 Antibiotics are a method of
combating infectious disease.
 Attack microorganism’s cells or
cellular process
 Do not harm human cells
Immune System: 2
components. Specific and
Nonspecific Immunity

Nonspecific Immunity is the first line of defense.
 Provide a general defense against al pathogens
 Slows progression of disease while specific
immunity kicks in
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Barriers: Prevent pathogens from entering the
body
 Skin – physical barrier
 Layers of dead skin cells and waxes coating the living
cells beneath.
 Chemical – attacks incoming pathogens
 Saliva, tears, mucus contain enzymes (lysozyme) that
attacks and destroys bacteria cell walls.
 HCl in the stomach kills bacteria if they enter
Nonspecific Response
 Cellular defense – A type of
White Blood Cells (WBC)
called macrophages
undergo phagocytosis.
 Interferon – cells infected
with a virus secrete a
protein called interferon
which stimulates neighbor
cells to make antiviral
proteins.
Inflammatory response
Damaged tissue and invading cells release
proteins which allow for WBCs to get to the
area.
Specific Immunity – Involves
Lymphatic System
 The lymphatic system
filters blood and lymph
and destroys
microorganisms.
 Destroys fat
 Lymph is a clear fluid that
bathes body cells and is
collected by lymph
vessels.
Lymphatic Organs
 Each of the following organs is made of
lymph tissues, lymphocytes, and
connective tissue.
 Lymph nodes
 Tonsils
 Spleen
 Thymus
Components to the
Immune System
 Macrophages – phagocytosis
 Helper T Cells – activate B
and cytotoxic T cells
 B Cells – Create antibodies
and memory cells
 Cytotoxic T Cells – direct
attack on invading pathogens
Specific Immunity – B Cell
Response
 B Lymphocytes are found in
all lymph tissue. They have
the role of being antibody
factories.
 Antibodies are proteins made
by B lymphocytes that target
specific foreign antigens.
 Antigens are anything foreign
to the body that cause immune
responses.
B Cell Response
 Macrophages present
antigens on their
surface. This antigen is
called a processed
antigen.
 The macrophage then
binds to a helper T Cell
(Another type of
lymphocyte).
 The helper T Cell is now
considered “activated”.
B Cell Response
 The activated helper T Cell go on to
activate B cells and cytotoxic T
cells.
 When activated B Cells divide and
mature into plasma cells and are
given instructions to make specific
antibodies to the antigen found.
 The activated B cell creates the
active plasma cell and memory
cells.
B Cell Response
 The antibodies
attach to the
foreign antigen and
cause clumping,
making it easy for
macrophages to
destroy them
T Cell Response
 The helper T cells also
activate cytotoxic T cells.
 1. These cytotoxic T cells
release cytokines which
signals the immune system
to activate.
 2. The cytotoxic T cells also
directly attack pathogens
and destroy them.
Types of Immunity
 Primary Response – first response to an
invasion in the body.
 Passive Immunity – A form of temporary
protection against a pathogen. The antibodies
are made by other humans/animals and
injected into the infected patient.
 Done for people exposed to rabies, tetanus,
hepatitis and venoms.
 Also done by pregnant mothers, passing antibodies
through the placenta to the developing fetus.
Types of Immunity
 Active Immunity – The memory cells
produced by B cells maturing are
involved in long-term memory of
pathogens.
 This type of immunity is a result from
a previous infection OR
immunization.
 Immunization is when a weakened/dead
strain of a pathogen is injected into the
body so that a first response can occur
Booster Shots
 After the first
injection antibodies
are made.
 A second injection
is made to further
boost the amount
of
antibodies/memory
cells made.
Immune System Failure
 Certain disease attack the immune
system directly.
 HIV is a virus that infects helper T cells.
 These T cells become HIV producing
factories.
 As a result the immune system cannot
fight other diseases over time.