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Immunity
Chapter 40
What is a disease?
• Any change that
disrupts the normal
function of the body
• Not caused by injury
• Causes = Genetic
(DNA mutation),
Pathogens (bacteria),
Environmental
(smoking)
Pathogens
• Disease-causing
agents
• “sicknessmakers”
• infectious
diseases
• (ex.) protist,
bacteria, virus,
worm, fungi
Germ Theory of Disease
• Ancient Times = diseases
caused by curses, evil
spirits, vapors, etc…
• 1800’s = Louis Pasteur and
Robert Koch = infectious
diseases were caused by
microorganisms of
different types called
germs
How do you know what
causes the Disease?
• Kochs Postulates:
1. Pathogen found in sick organism and not
healthy organism
2. Pathogen is isolated and grown in a lab
3. Pathogen is placed on a healthy organism
and it develops the disease
4. Pathogen from injected host is isolated
and it is identical to the original pathogen
Koch Postulate Example
• Allen Steere (1975)
– Several children in a small area with the same
symptoms (rash, arthritis)
– All children had tick bites
– Ticks have the bacteria Borrelia burgdorferi
– Isolate the bacteria, grow it, put it in lab rats
– Lab rat gets sick with same symptoms
– bacteria isolated from sick rat
– Ticks with the bacteria cause Lyme Disease
Why do Pathogens like us?
• Our body temperature
is good for growth
• watery environment
(most pathogens
dehydrate easily)
• abundance of
nutrients (eat us or
our food)
How does a pathogen
infection result in Disease?
• Viruses = take over
and kill cells,
disrupt normal
function of the cell
• Bacteria = 1)
destroy tissue for
food or 2) release
harmful toxins
How does a pathogen
infection result in Disease?
• Protists = mostly by feeding
off of our nutrients and
sometimes producing harmful
toxins
• Worms = Disrupt normal cell
function, eat tissue, eat
nutrients
• Fungi = disrupt normal cell
function (usually skin cells)
How do diseases
spread?
1. Physical Contact:
coughing, sneezing,
physical contact
2. Contaminated food and
water
3. Infected Animals
(vectors)
Antibiotics
• Discovered by Alexander Fleming (1928)
• Compounds that kill bacteria without killing
other cells within the host
• Most are naturally occurring (fungi, sulfur
based) and some are synthetic
• They have no effect on viruses
• Over-the-counter drugs only treat the
symptoms
Immunity
Chapter 40
Your Immune System
• Fights off
infections
• Produces cells that
search and destroy
foreign cells
(immunity)
• 2 types of
Defenses: Specific
and Non-Specific
Non-Specific Defenses
1.
The Skin: (1st
line of Defense)
- keeps
pathogens out
of the body
- protective seal
- If broken,
pathogens can
get in (swelling,
redness, pain)
Non-Specific Defenses
• Body Fluids: (1st line of Defense)
– Saliva and Tears = contain
lysozyme that breaks down
bacteria cell walls
– Oil and Sweat = make the skin
acidic which kills bacteria too
– Mucus = traps pathogens that try
to enter the mouth and nose
– Stomach Acid = destroy any
pathogen that makes it to the
stomach
2. Inflammatory
Response (2nd Line
of Defense)
- white blood cells
are produced
- blood vessels
expand (more
circulation)
- Fever = increased
body temperature
kills some
pathogens and it
also increases the
heart rate so WBC
get there faster
Non-Specific
Defenses
Non-Specific
Defenses
• Interferon
– how your body reacts to
a viral infection
– released from infected
cells to prevent other
cells from being infected
– slows down the infection
by blocking viral
replication
Specific Defenses
Cell Types:
- B-Cells = protect against
infections in the body’s
fluids
- T-cells = protect against
abnormal cells and
infections within cells
Specific Defenses
• More Cell Types:
- Antibodies = proteins that
attack pathogens
- Memory Cells = cells that
remember how to kill specific
pathogens
- Antigens = a substance that
triggers an immune response
(start button)
Humoral Immunity
1. A pathogen infects a body fluid
2. Antigens trigger the production of
more B-cells and Plasma Cells
3. Plasma cells produce antibodies
4. Antibodies kill the pathogen
5. Memory cells are made to remember
how to kill that pathogen next time
Cell-Mediated Immunity
1. Cells become cancerous or are infected
with a virus, fungi, or protist
2. T-Cells turn into 4 types and the Stop the
Infection:
– Killer T-Cells: destroy the pathogen
– Helper T-Cells: produce memory T-cells
– Memory T-cells: remember how to kill pathogen
for next time
– Suppressor T-cells: tell killer T-Cells to stop
Organ Transplants
• Every cell has a marker on it
that identifies it to the tcells (ID card)
• T-Cells check the ID’s and
destroy anything that doesn’t
belong
• We can transplant organs by:
– 1. Picking a donor with
similar ID cards
– 2. Suppressing the t-cells
after a transplant
Active Immunity
• Vaccinations:
– A weakened dose
of a pathogen
– Safe 1st response
– 20 vaccinations
currently available
– Natural and
synthetic
Passive Immunity
• Antibodies produced by
one animal are placed
inside another animal
• Only lasts a short time
because the foreign
antibodies will be killed
by T-cells
• Mothers pass on
immunity to their
children through the
placenta and breast milk
Allergies
• Overreaction of the
immune system
• allergens (pollen, dust, bee
stings, food) trigger a
immune response
• Histamines - chemicals
released during an allergic
reaction
– cause sneezing, watery
eyes, mucus, increased
blood flow, etc...
Auto-Immune Diseases
• When the immune system
attacks the body’s own cells
instead of foreign cells
• Multiple Sclerosis (MS) =
immune system attacks the
nervous system
– loss of mobility
– numbness
– loss of balance
AIDS
• Caused by the HIV virus
• the HIV attacks and kills T-Cells
• Without T-Cells, body is unable to fight
disease