Transcript Document

The Human Immune System
Did you know?
• In the mid-1300’s, 25 million people died from the
plague which was caused by a bacterial pathogen
carried by the fleas on rats.
• Around 1850, a British surgeon named Joseph Lister,
wondered if pathogens were being transferred from
surgeons hands and medical equipment to patients.
After surgeons started to clean their hands, scalpels
etc. the death rate fell significantly!
Four Ways to Transmit Infectious Diseases
DIRECT Contact
 Shaking hands
 Sharing Drinks/Food
 Sharing Bodily Fluids
INDIRECT Contact
 Being near an infected person
 Sneezing
 Coughing
*Some pathogens can travel up to 5m*
WATER & FOOD




ANIMAL BITES
 Bitten by an animal carrying the
rabies virus
Eating infected foods
E. coli
Salmonella
Coliform
What is the IMMUNE system?
• The body’s defense against disease causing
organisms, malfunctioning cells, and
foreign particles.
Your immune system has
powerful defences to fight
pathogens that are constantly
attacking your body…..
*THE FIRST LINE OF DEFENCE*
*THE SECOND LINE OF DEFENCE*
The First Line of Defence ~Skin~
- The dead, outer layer of skin, known
as the epidermis, forms a shield
against invaders.
- Dead skin cells are constantly
sloughed off, making it hard for
invading bacteria to colonize.
- Sweat and oils contain anti-microbial
chemicals, including some
antibiotics.
- You shed between 40 – 50 thousand
skin cells every day!
The First Line of Defence ~Mucus and Cilia~
-
As you breathe in, foreign particles and
bacteria bump into mucus throughout your
respiratory system and become stuck.
-
Mucus contains lysozymes, enzymes that
destroy bacterial cell walls.
-
The normal flow of mucus washes bacteria
and viruses off of mucus membranes.
-
Hair-like structures called cilia sweep this
mucus into the throat for coughing or
swallowing.
-
Cilia in the respiratory tract move mucus
out of the lungs to keep bacteria and viruses
out.
The First Line of Defence ~Saliva and Tears~
- Saliva and tears contain many chemicals
and enzymes that break down bacteria.
- However, there are thousands of different
types of bacteria can survive these
chemicals.
The First Line of Defence ~Stomach Acid~
- Swallowed bacteria and pathogens
are broken down by an incredibly
strong acidic gastric juice that is
secreted by the lining of the stomach.
- The stomach must produce a coating
of special mucus or this acid would
eat through the stomach!
The Second Line of Defence
• If a pathogen makes it past the
first line of defence then your
body launches an attack against
the pathogen.
• Your body needs to be able to
distinguish between invading
cells and cells that belong. Once
it realizes the unknown cell is an
invader, it will launch the attack.
The Second Line of Defence
• There are two types of immune responses.
*INNATE Immune Response
-a response we are born with
*ACQUIRED Immune Response
-a highly specific response our bodies
must build
The Second Line of Defence
Innate Immune Response ~Inflammation~
- The first action of the Innate Immune
Response is the flow of FLUID,
CELLS and dissolved substances from
the BLOOD to the site of infection.
- This causes fever, swelling and
redness – which is known as
INFLAMMATION.
- White blood cells, called
PHAGOCYTES, increase. Their job
is to search for invading pathogens and
destroy them.
Video
The Second Line of Defence
Innate Immune Response ~Phagocytes~
• These white blood cells are
responsible for eating
foreign particles by
engulfing them.
• Once engulfed, the
phagocyte breaks the foreign
particles apart in organelles
called Lysosomes.
In Greek, phago
means to eat, and cyte
means cell.
The Second Line of Defence
Acquired Immune Response
• This is a highly specific attack on a
pathogen or antigen.
– PATHOGEN: Disease causing organism or
substance.
– ANTIGEN: Any substance the body cannot
recognize, from a virus to a splinter.
The Second Line of Defence
Acquired Immune Response
Mobilization
Disposal
Recognition
Immunity
B Cell
White
Blood Cell
Nucleus
Helper T Cell
Pathogen
Memory B Cell
Antibody
The Second Line of Defence
Acquired Immune Response
Recognition
White blood cells surround the pathogen and signal T Cells.
More T Cells are produced. Then the Helper T Cells signal the
B Cells.
Mobilization
B Cells produce antibodies.
Disposal
Antibodies destroy pathogens and antigens.
Immunity
Some antibodies (Memory B Cells) remain for future use. This
is called “Active Immunity”.
The Second Line of Defence
Acquired Immune Response
• This response can take up to a week to develop,
because your body needs time to develop the
exact response needed to defeat the particular
invader.
• Another type of T Cell is called a ‘Killer T Cell’.
Killer T Cells can work independently and
directly destroy antigens or pathogens. They
also destroy cancer cells.
Viruses
 Viruses are non-living particles that enter body cells, hijack
their organelles, and turn the cell into a virus makingfactory. The cell will eventually burst, releasing thousands
of viruses to infect new cells.
 If you have ever heard of HIV, chicken pox, cold sores or
the flu – then you have heard of viruses.
*A virus will insert
its DNA into the
nucleus of the host
cell and ‘trick’ the
cell into making
new virus particles.
Cell before infection…
…and after.
What is Immunity?
- Resistance to a disease causing organism or
harmful substance.
- Two types
- Active Immunity
- Passive Immunity
Active Immunity
- You produce the antibodies
- Your body has been exposed to the antigen in the
past either through:
- Exposure to the actual disease causing antigen – Your
immune system fought it, won, and Memory B Cells
remain.
- Planned exposure to a form of the antigen that has been
killed or weakened – Your immune system detected it,
eliminated it, and remembered it.
Vaccines
• Antigens are deliberately introduced into the immune system to
produce immunity. This is done through immunizations when you
are a baby, through to adulthood.
• The vaccine is a weakened form of the disease. It stimulates the
immune system to create antibodies against the disease. The
antibodies are then reactivated if ever the disease enters your
body again.
• Vaccines have eradicated or severely limited several diseases
from the face of the Earth, such as polio and smallpox.
How long does active immunity last?
• It depends on the antigen.
• Some disease-causing bacteria multiply
into new forms that our body doesn’t
recognize, requiring annual
vaccinations, like the flu shot.
• Booster shot - reminds the immune
system of the antigen.
• Others last for a lifetime, such as
chicken pox.
Passive Immunity
• You don’t produce the antibodies
– A mother will pass immunity
onto her baby during pregnancy
through the placenta. These
antibodies will protect the baby
for a short period of time
following birth while the baby’s
immune system develops. The
immunity will last until the
antibodies die.
Think the flu is no big deal?
- Think again…
- In 1918, a particularly
deadly strain of flu, called
the Spanish Influenza,
spread across the globe.
- It infected 20% of the
human population and
killed 5%, which was about
100 million people.
Immune Disorders ~Allergies~
- An allergy is an unusually high sensitivity to some substance.
If this substance causes an allergic reaction, it is known as an
allergen.
* Examples of allergens are: foods, pollen, dust and animals.
- Symptoms of allergies include sneezing, runny nose, watery
eyes, rash, and swelling. These symptoms result from a side
effect of a substance called histamine.
- Anti-histamines block the effect of histamines and bring relief
to allergy sufferers. They do not cure the allergy, they just
reduce the symptoms.
Immune Disorders ~Allergies~
• Some people are highly allergic to allergens (such
as bee stings or peanuts). Exposure to these
allergens can trigger anaphylactic shock which
can result in swelling, difficulty breathing, and
sometimes death. For this reason, people with
these allergies must carry an Epipen with them.
Immune Disorders ~ Acquired Immune
Deficiency Syndrome (AIDS)
• Caused by the Human Immunodeficiency
Virus (HIV).
• Discovered in 1983.
• It is a powerful pathogen that attacks the
immune system and specifically targets and
kills Helper T-cells.
• This means that when other pathogens enter
the body, the immune system is unable to
activate Killer T cells or B cells.
• A person infected with HIV can die from other
infections as a result from their weakened
immune system.
HIV is transmitted
through:
-body fluids
-semen
-blood
-unprotected sex
-sharing needles
-blood transfusions
Taking Care of Your Immune System
• Eat a well balanced diet.
• Maintain your personal hygiene (brush your
teeth, bathe, wash your hands often).
• Keep your home clean.
• Get plenty of rest and exercise.
• Keep your vaccinations up to date.
• Avoid tobacco and other non-prescription drugs.
• Do not engage in activities that involve sharing bodily
fluids with others.
•
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