Transcript The Immune System - John Burroughs Middle School

The Immune
System
“Bad boys, bad boys, whatcha gonna
do when they come for you?”
Pathogens Vs. White Blood Cells
Terms to Know
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Pathogen
Communicable disease
Non communicable disease
Immune system
Bacteria
viruses
Leukocytes
Phagocytosis
T lymphocytes
B lymphocytes
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Immunity
Spleen
Thymus gland
Bone marrow
Allergic response
Antigen
Antibody
Innate and passive
immunity
• Interferon
• inflammation
Communicable Diseases
• These are diseases that are contagious
• They are caused by a pathogen, a disease
causing organism, or chemical.
• Examples of communicable diseases:
pneumonia, common cold, tuberculosis,
chicken pox, HIV, and more
• Samantha goes to the bathroom in a public restroom
where several people infected with the flu just used
the same bathroom. What tips can you give
Samantha to help prevent her from contracting the
flu virus germs?
• Use a paper towel to flush toilet and open the door
of the bathroom stall door
• Use a paper towel to turn off the faucet after you
wash your hands to avoid recontamination
• Scrub your hands with soap for at least 15 seconds
• Open the door with a paper towel to exit the
restroom
Non-Communicable Diseases
• Diseases that are not contagious
• Examples: cancer, genetic diseases, diabetes,
cirrhosis, emphysema, etc
Types of
Pathogens
Bacteria
Fungi
Viruses
This is a picture of
a bacterium, a
prokaryote cell
Notice, it does not
contain a nucleus
DNA is coiled up in
the center
BACTERIA
• These are a large group of unicellular
organisms
• They come in three shapes: sphere, rod, and
spiral shaped
• They can be found everywhere on Earth- in
soil, acidic hot springs, water, and deep in the
earth’s crust
• There are large number of bacterial cells in
the human digestive tract and skin
• Most bacteria are not harmful, and some are
beneficial- antibiotics are used to destroy bacteria
Viruses
Viruses are infectious
agents that are not able to
grow outside a host’s cellthey take over the host’s
DNA to make more copies
of their cells
Viruses are 100 times
smaller than bacteria
Contain-DNA and RNA,
protein coat, and a tail.
Some have an envelope of
fat to protect them when
outside a host
HIV-Human Immunodeficiency Virus- the virus
responsible for causing AIDS
Functions
• The immune system is the body’s defense
against infectious organisms and other
invaders
• Through a series of steps called the immune
response, the immune system attacks
organisms and substances that invade our
system and cause disease
The Body’s First Line of Defense
• Billions of bacteria are floating around every second of your life,
most of them harmless to you
• Openings through which bacteria enter the body are the mouth,
ears, nose, eye, or cut in skin
• Your skin is your first line of defense against them. It does
its best to keep out bacteria and other pathogens
The Second Line of Defense
• Mucus/cilia-mucus in the nasal passageway
and upper respiratory tract help trap
pathogens, while cilia sweep them away
• Earwax-helps trap in foreign material
• Tears and sweat- have anti-microbial agents
called lysozyme
• Saliva- destroys harmful organisms in the
mouth because it also has lysozymes
• Stomach acid- kills some pathogen that enter
with food
White Blood Cells-The Body’s
Third Line of Defense (the “cops”)
• The cells that are part of the immune system are the white blood
cells, also called leukocytes
• They are produced or stored in may places in the body including
the thymus gland, spleen, and bone marrow
• There are also clumps of lymphoid tissue, primarily lymph
nodes, that house leukocytes
• When pathogens have slipped passed the first and second line of
defenses- your WBC’s step in to help
Some leukocytes are produced in the
thymus and in the spleen
Spleen
• A small organ located just under the left diaphragm
• It creates lymphocytes for the destruction and
recycling of old red blood cells
• It is also a blood reservoir, supplying the body blood
in the case of an emergency, such as a bad cut
• It is also the location where white blood cells trap
microorganisms
The Inflammatory Response
When you have a cut, bee sting, or splinter in
your finger- here is what happens:
1. Blood supply to the area increases and
circulation in that area decreases.
2. Blood pressure in the area increases causing
blood to leak from the blood vessel.
3. As a result, swelling, pain, heat, and redness
happens- this is called inflammation
The Inflammatory Response
Two Types of Leukocytes
(white blood cells)
• PhagocytesThese are the white
blood cells that chew
up, or eat invading
organisms
• LymphocytesThese are the white
blood cells that allow
the body to remember
and recognize previous
invaders
Phagocytosis
• Neutrophils and other
phagocytes engulf their
bacteria, or other invader,
through a process called
phagocytosis
• Any molecule that binds to
a microorganism and
speeds phagocytosis is
called an opsonin
(antibodies are an example)
A white blood cell “engulfing”
bacteria
Neutrophil
• This is the most common
type of phagocyte in the
immune system, makes up
about 65% of WBC’s
• They primarily fight bacteria
When doctors are worried
about a bacterial infection,
sometimes they order a
blood test to see if a patient
has an increased number of
neutrophils, triggered by
the infection
Heat as a Way to Kill Germs
• Some phagocytes
release chemicals that
cause a fever. The high
temperature doesn’t
make you feel so good,
but it does help to kill of
some of the disease
causing germs. Germs
prefer a temperature of
98.6degrees
Other phagocytes
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Basophils
Neutrophils
Monocytes
eusonophils
All lymphocytes start off in the bone
marrow. There are two types:
• B lymphocytes- these
are the lymphocytes
that stay in the bone
marrow and mature
into B cells
• B cells produce
antibodies
• T lymphocytes- these
are the lymphocytes
that leave the bone
marrow to go to the
thymus gland and
mature into T cells
Antibodies and Antigens
• Each germ has proteins called
antigens on their surface
• An antigen is a molecule, usually
a protein, that acts as a marker
for cells, as well as bacteria,
viruses, or any other foreign
substance that enters the body
• Antibodies are proteins that
attach to the germ’s antigens
preventing the germ from
infecting cells
• Antibodies are made by the B
cells
Antibodies and Antigens Fit Together Like a
Lock and Key
How it Works
• A foreign substance, an antigen, enters the body
• When it is detected, several types of cells work together to recognize and
respond to it
• These cells trigger B lymphocytes to produce antibodies
• The antibodies lock onto specific antigens, so that they can no longer
infect other cells
• Once the B cells have produced antibodies, these
antibodies continue to persist in a person’s body
• That means if the same antigen is presented to the
immune system again, the antibodies are ready to do
their job
• That is why if someone already got sick from the
chicken pox, the person is not likely to get sick from it
again
• This is also why we use immunization to prevent
getting certain diseases
• Although antibodies can recognize an antigen
and lock on to it, they are not capable of
destroying it without help
• The T cells are the part of the system that
destroys the antigens tagged by the
antibodies, or cells that have been infected or
somehow changed
• T cells also signal other cells, like phagocytes,
to do their jobs
Helper T cells
• Helper T cells are in
command
• They control the entire
system and give orders
about how to destroy
the germs
• Basically, they signal B
cells and killer T cells to
come to the rescue at
an infection site
B cells
• B cells leave the bone
marrow to fight germs
with their antibodies
• They mark germs with
antibodies
Killer T cells
• These cells bump into
infected cells, poke
holes into them and
destroy
Suppressor T cells
• Suppressor T-cells get
there when the battle is
over and it looks safe
• They tell the killer Tcells to stop fighting
Memory T cells
• Memory T- cells are
sent after the
suppressor T- cells
• They patrol the area
and watch for a germ’s
return
• If the germ returns,
they alert the system
which already has a
strategy for fighting this
germ
Allergies
• Sometimes immune cells have poor
recognition capabilities and mistake a
harmless allergen for a dangerous pathogen
• This results in an inappropriate allergic
response
Immunity
• All of these specialized cells and parts of the
immune system offer the body protection
against disease
• This protection is called immunity
• Humans have three types of immunity- innate,
active, and passive
Innate Immunity
• Everyone is born with innate (or natural/born with it)
immunity, a type of general protection everyone has
• Many of the germs that affect other species, don’t
harm us
• For example, viruses that cause leukemia in cats or
stemper in dogs, don’t harm humans
• Vice versa, some viruses, such as HIV, make humans
ill, but not cats or dogs
Active Immunity
• We also have a second kind of protection
called active immunity where immunity
develops throughout our lives
• Active immunity involves lymphocytes and
• It develops as children and adults are exposed
to diseases or immunized against diseases
through vaccination
Passive
Immunity
• Passive immunity is
“borrowed” from another
source and it lasts for a
short time
• For example, antibodies in
a mother’s breast milk
provide an infant with
temporary immunity to
diseases that the mother
has been exposed to
• This can help protect the
infant against infection
during the early years of
childhood
We Are All Different
• Everyone’s immune system is different
• Some people never seem to get sick whereas others
seem to be sick all the time
• As a person gets older, he or she usually becomes
immune to more germs as the immune system
comes in contact with more and more of them
• That is why adults and teens tend to get fewer colds
than children- their bodies have learned to recognize
and immediately attack many of the viruses that
cause colds
One Last Note
• The thymus gland begins to shrink
after the age of sixty or so, due to a
drop in the production of the HGH
(human growth hormone).
• This results in the production of less T
cells, this is one reason elderly people
have a harder time fighting off an
infection than young people do
Ways To
Care For Your
Immune System
#1 Avoid The Use of Drugs- Drugs and
Drinking Too Much Alcohol Can weaken the
Immune System
#2 Eat Healthy
Foods
Fruits
Vegetables
Whole Grains
Lean Meats
And occasionally treat
yourself to a bite of
chocolate or a cup of
low fat ice cream (or
Pinkberry’s)
#3 Reduce the
Amount of Stress
in Your Life
Don’t wait until the last
minute to study for a test or
work on a project, this can
cause stress- plan ahead
Take a little time each night
to do some school work
See your teachers,
counselors, or parents if you
need help with school work
or anything else that is on
your mind
Because Stress Can Weaken the Immune
System, making it easier to get sick
So, #4 is Find Time to Relax
Just Relax a Bit
And Tell Your Parents to Take You to The Beach
this weekend- tell them it will help you relax and
strengthen your immune system 
And maybe end the day with an
ice cream cone 