Section 3.3

The Enemies of our Immune System
 Pathogens are harmful organisms that can invade the body and cause disease.
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Includes viruses, bacteria, parasites, and fungi
1700’s
E.g.
Smallpox
(pox virus)

E.g. Bacteria - Cholera

E.g. Fungi – Athletes Foot (Tinea pedis)

E.g. Parasite – Common roundworm (Ascaris lumbricodois)

Our Body’s Immune System
 Innate Immune System
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1 st immune response (within hours)
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Phagocytes in the body attack the parasites at the site of infection.
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They recognize pathogens by identifying their antigens and then engulf the parasites.

Antigens are proteins that are located on the surface of a pathogen (each pathogen has a unique antigen)

 Adaptive Immune System
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2 nd immune response (days to weeks after parasite enters)
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The adaptive immune system produces antibodies which will attack the pathogens
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They will also form memory cells to protect the body from the same pathogen

Vaccinations – E.g. Virus
 A vaccine for the flu is composed of antigens from the influenza virus.
 The body will then produce antibodies that are specific to the influenza virus.

If the flu virus infects an individual after the flu shot, their body will have a stronger immune response
 therefore killing the virus.

Vaccine Controversy - Pros
 If used widespread, the vaccine can eliminate a harmful pathogen


E.g. smallpox virus
E.g. rubella virus (German measles)
 Vaccines allow the human body to prepare for infection in a manner that is more safe than being exposed to the pathogen without vaccination.

Vaccination Controversy - Cons
 Vaccines tend to produce side effects.
 The side effects vary between vaccine but range from:

Redness, swelling, itching, bruising, headache, nausea, severe allergic reactions, tiredness, vomiting, seizure, fevers, coma & brain damage (rare),

Vaccines are expensive to produce

The Canadian government spent 2 billion in vaccines against H1N1
 Vaccinations can be dangerous for children

Vaccines may accelerate the rate of pathogen evolution

Super bugs

The Community Immunity Dilemna
 If a small percentage of the population receives a vaccination, then the virus (or other pathogen) will be able to survive and harm many people.

All the individuals who took the vaccine were susceptible to the side effects.
 If a large percentage of the population receives a vaccination, then everyone is protected. Even those that did not receive the vaccination.

Independent Reading – Stopping the Spread of
Disease (page 112-114)
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
Read pages 112-114
Answer questions 5-8 (page 115)

Thursday Work Activity 3-C
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Read pages 119-120
Answer all questions on page 120
Include a title page