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BC Science 8
Chapter 3
3.1
The Immune System
Infectious Diseases
- are caused by pathogens
Pathogen
- an organism or substance that can
cause a disease
Antigen
- is a non-living particle or
substance that the body cannot
recognize (ex. A virus)
Phagocytes
- white blood cells that fight
Infections
4 Ways to Transmit Infectious Diseases
Transmission Method
Example
Direct Contact
Shaking hands or sharing drinking
containers or bodily fluids with an infected
person
Indirect Contact
Being near an infected person who sneezes
without covering his or her mouth. Some
pathogens can travel up to 5 m and infect
people within that range
Water and Food
Eating foods, such as eggs and some meats
that are infected with Salmonella bacteria.
Drinking water infected with E. Coli
bacteria can also result in serious illness.
Animal Bites
Being bitten by an animal carrying the
rabies virus
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BC Science 8 – Chapter 3
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How does the Immune System protect the body?
 The immune system is the body’s defence system.
 The immune system attacks and destroys invaders such as pathogens
entering the body
 2 lines of defence
First Line of Defence
 The first line of defence is the skin and the linings of the body’s
internal systems.
 The skin stops many pathogens from entering the body.
 Sweat and oils on your skins can kill pathogens.
 Gastric juice can destroy pathogens that enter the stomach.

Mucus and cilia in your nose prevent pathogens from entering your
respiratory system.
Figure 3.3
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BC Science 8 – Chapter 3
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The Second Line of Defence
 The second line of defence is to respond to pathogens by attacking
them.
 2 ways the immune system attacks pathogens are an innate immune
response and an acquired immune response.
Innate Immune Response
 Is a quick, general response that all living things are born with.
 When pathogens attack, the body makes more white blood cells or
phagocytes (the blood cells that fight infections)
 The white blood cells are sent to the infected part of the body, causing a
fever, swelling, and redness in the area (inflammation).
 The white blood cells (phagocytes) swallow up the invading pathogens.
Figure 3.5
Eric Hamber Secondary
BC Science 8 – Chapter 3
figure 3.6
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Acquired Immune Response
 An acquired immune response is a specific attack on a particular
pathogen, or antigen and there are 2 ways the body can mount an
attack.
 Both ways involve types of white blood called B cells and T cells
B cells
 Recognize antigens in the body
 Produce antibodies to fight the antigens
 Antibodies attach to and destroy antigens and pathogens carrying
antigens.
Figure 3.7
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T Cells – Helper T Cell and Killer T Cells
 White blood cells recognize an antigen or pathogen and signal for helper
T cells which activate B cells to produce antibodies to attack them
 The antibodies then destroy the antigen or pathogen

Some of the antibodies stay in the body to protect against future
infections (immunity)
Figure 3.8
 Killer T cells can work independently and directly destroy antigens or
pathogens
Figure 3.9
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Active Immunity
 All Acquired immune responses help give you active immunity.
 This means your body remembers which antibodies should be used to
attack a pathogen that has infected it before
 After the first infection, your body stores some of the newly produced
antibodies on B cells
 B cells or memory B cells can be re-activated if the antigen or pathogen
reappears.
3.2 Factors Affecting the Immune System
 Mary Montagu
- discovered a way or protecting
children from smallpox by making a
scratch on a child’s arm and placing a
drop of pus from a mildly infected
person onto the scratch. Children
would recover quickly from a milder
version of smallpox
 Edward Jenner
- 1796, discovered that people who
milked cows seemed to be immune to
smallpox because they had previously
had cowpox. (If people got cowpox;
they could not get smallpox)
 Vaccine
- is a weakened or dead form of a
disease pathogen. A vaccine is a
special version of an antigen that
gives you immunity against a disease
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 Allergy
- your immune system is very
substance, such as dust, mould, or
some foods
 Allergen
- any substance that causes an allergic
reaction (ex. Runny nose, watery
eyes)
 Histamine
- a chemical the immune system
releases to combat allergens when
they enter the body
 Anaphylactic shock
- a severe reaction from exposure to
Allergens (ex. Bee sting venom and
Peanuts) ….reactions like swelling,
Breathing difficulty, and sometimes
Death. Carrying an adrenaline autoInjector to inject adrenaline into the
Body to counter the allergic reaction
 AIDS
(Acquired Immunodeficiency
Syndrome)
- a disease that is caused by a type of
virus called HIV
 HIV
(Human Immunodeficiency
Virus)
- a pathogen that attacks the helper T
cells of the immune system and
without helper T cells, the body
cannot trigger the action of killer T
cells or B cells (a person can get very
sick or die from infections)
diagram
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Taking Care of Your Immune System
 Eat a well balanced diet.
 Maintain your personal hygiene – brush your

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

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teeth, shower or bathe, and wash your hands often.
Keep your home clean.
Avoid tobacco and other non-prescription drugs.
Get plenty of rest and exercise.
Keep your vaccinations up to date.
Do not engage in activities that involve sharing
body fluids with others.
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