Download The Immune System

The Immune System
Infectious Disease
• Pathogens are disease-causing “invaders”
• Infectious diseases can be spread by contact with infected people,
animals, water, or food.
• Four ways to transmit infectious diseases (with examples):
Direct contact: shaking hands or sharing drinks or bodily fluids with an
infected person
Indirect contact: being near an infected person who sneezes without
covering his or her mouth
Water and food: eating foods infected with certain bacteria, ex, Salmonella.
Drinking water infected with E.coli bacteria can also result in serious
illness.
Animal bites: being bitten by an animal carrying rabies
Immune System:
First Line of Defence
• The skin and the
linings of all internal
body systems. Sweat
and oil are acidic.
• Gastric juice is acidic,
and can destroy
pathogens.
Second Line of Defence: Innate
Immune Response
• Quick and general
• Usually fight bacteria and
some viruses.
• First action is a flow of fluid,
cells, and dissolved
substances to the infection
site.
• Fever, inflammation and
redness occurs.
• A type of white blood cells
called phagocytes will
increase in number.
• The phagocytes engulf and
swallow the pathogens.
Acquired Immune Response
• Highly specific attack on a pathogen, or antigen.
• An antigen is any substance the body cannot recognize, it is a
non-living particle or substance
• Your body uses WBC’s called B cells and T cells to respond.
• The process can take up to a week.
• B cells recognize antigens and produce specific particles, called
antibodies to fight them.
• Antibodies attach and destroy antigens and pathogens carrying
antigens.
• T cells: helper T cells recognizes an antigen or pathogen
and activates B cells.
• T cells: killer T cells work independently and destroy
antigens or pathogens.
• All acquired immune responses help give you active
immunity. Your body remembers which antibodies should
be used to attack a pathogen that it has seen before.
• Memory B cells store the new antibodies
Factors Affecting the
Immune System
Vaccinations
• Vaccines: a special version of
an antigen that gives you
immunity against a disease.
• Vaccines are like weakened
forms of a disease, they
stimulate your immune system
to create antibodies against the
disease.
• These antibodies are
reactivated to fight the antigen if
it enters your body.
• Some vaccines require booster
shots.
• All grade 9 students receive
booster shots for tetanus,
diptheria, and pertussis.
Disorders of the Immune System
• Allergies: an unusually high
sensitivity to some substance.
• Something that causes an
allergic reaction is an allergen.
• The allergen acts as an antigen
for you, and your immune system
kicks in.
• The symptoms of an allergy are
cause by a substance called
histamine, that your body
releases.
• A severe reaction to an allergen
is called anaphylactic shock, and
can result in breathing difficulty,
swelling, and sometimes death.
Acquired Immunodeficiency Syndrome (AIDS)
• AIDS is an infection of the immune
system.
• AIDS is caused by the human
immunodeficiency virus (HIV).
• HIV attacks the immune system itself, and
destroys it by infecting helper T cells.
• The immune system becomes unable to
defend against pathogens or antigens.
• A person infected with HIV can die from
other, less serious infections.
• AIDS has resulted in the death of more
than 11 million people, and currently
affects more than 40 million people.
• HIV is transmitted in two body fluids,
semen and blood.
• People are infected by unsafe behaviour,
such as having sex with a person who has
HIV without using a condom, or sharing
contaminated needles.
• HIV cannot be transmitted by casual
contact such as shaking hands.