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The Immune System


									   The Immune
“Bad boys, bad boys, whatcha gonna
   do when they come for you?”
  Pathogens Vs. White Blood Cells
                  Terms to Know
•   Pathogen                   • Immunity
•   Communicable disease       • Spleen
•   Non communicable disease   • Thymus gland
•   Immune system              • Bone marrow
•   Bacteria                   • Allergic response
•   viruses                    • Antigen
•   Leukocytes                 • Antibody
•   Phagocytosis               • Innate and passive
•   T lymphocytes                immunity
•   B lymphocytes              • 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
    Non-Communicable Diseases
• Diseases that are not contagious

• Examples: cancer, genetic diseases, diabetes,
  cirrhosis, emphysema, etc
Types of

This is a picture of
a bacterium, a
prokaryote cell
Notice, it does not
contain a nucleus
DNA is coiled up in
the center
• These are a large group of unicellular
• 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 are infectious
agents that are not able to
grow outside a host’s cell-
they 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
• The immune system is the body’s defense
  against infectious organisms and other
• 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
• 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
     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)
• Phagocytes-              • Lymphocytes-
  These are the white        These are the white
   blood cells that chew      blood cells that allow
   up, or eat invading        the body to remember
   organisms                  and recognize previous
• Neutrophils and other
  phagocytes engulf their
  bacteria, or other invader,
  through a process called
• Any molecule that binds to
  a microorganism and
  speeds phagocytosis is
  called an opsonin
  (antibodies are an example)
A white blood cell “engulfing”
• 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
             Other phagocytes
•   Basophils
•   Neutrophils
•   Monocytes
•   eusonophils
    All lymphocytes start off in the bone
        marrow. There are two types:
• B lymphocytes- these    • T lymphocytes- these
  are the lymphocytes       are the lymphocytes
  that stay in the bone     that leave the bone
  marrow and mature         marrow to go to the
  into B cells              thymus gland and
• B cells produce           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
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
• 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
• 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
                 Killer T cells
• These cells bump into
  infected cells, poke
  holes into them and
             Suppressor T cells
• Suppressor T-cells get
  there when the battle is
  over and it looks safe
• They tell the killer T-
  cells 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
• If the germ returns,
  they alert the system
  which already has a
  strategy for fighting this
• Sometimes immune cells have poor
  recognition capabilities and mistake a
  harmless allergen for a dangerous pathogen
• This results in an inappropriate allergic
• 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 is
Immunity     “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
                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
                • The thymus gland begins to shrink
One Last Note     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
Whole Grains
Lean Meats
And occasionally treat
yourself to a bite of
chocolate or a cup of
low fat ice cream (or
#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 

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