Transcript c. Section 1.3 The Immune System

Unit 1: Cells and Systems
Section 3: The Immune System
I. The Immune System and
Transmission of Infectious Diseases
• The immune system attacks and destroys
invaders that enter the body.
• Pathogens are organisms or substances that
cause disease (germs)
• Antigens are any non-living substance that is
foreign to the body and triggers an immune
response (i.e., splinter, plant pollen, viruses)
Diseases can be spread by:
• Direct contact (shaking hands, sharing body
fluids)
• Indirect contact (sneezing, coughing)
• Water and Food (eating foods or drinking
water infected with pathogens)
• Animal bites
II. Fighting Infections
a) 1st Line of Defense – Body prevents pathogens
from infecting host Skin and linings of all internal
organs
• Sweat and oil (slightly acidic, preventing some
pathogens from growing)
• Gastric juice secreted by the lining of the
stomach
• Mucus and Cilia (line the nose preventing
pathogens from entering respiratory system)
Describe what each of the following “entry points” do
to prevent entry of pathogens into the body:
“Entry point”
Entry blocked by…
Eyes
Tears, eyelashes
Ears
Ear wax
Nose
Mucus, cilia
Mouth (and
stomach)
Gastric juice
b) 2nd Line of Defense - Body mounts an
immune response to an attack
Two Types:
• Innate Immune Response
• Acquired Immune Response
I) Innate Immune Response - general,
non-specific (same for any invader)
• fluid, cells and dissolved substances in
the blood flow to the site of infection
• this results in fever, swelling, and redness
(inflammation)
• white blood cells in the blood engulf
intruders, destroying them – called
PHAGOCYTOSIS
https://www.youtube.com/watch?v=X-ubCIcAh4M
II) Acquired Immune Response - more
specific attack on a particular pathogen
• Consists of 4 stages:
1. Recognition
2. Mobilization
3. Disposal
4. Immunity
1. Recognition
• when body is invaded by a foreign
substance, the body recognizes it as not
belonging
• The body uses white blood cells to
recognize infection and to fight the
invading disease-causing agent, or
pathogen.
• Phagocytes engulf (eat) the invading bacteria
and signal Helper T cells to find B cells and tell
them to produce antibodies.
2. Mobilization
• B cells make antibodies, which bind to
antigens to make them harmless or mark
them for destruction by other white blood
cells
– Must have a perfect fit = lock and key
– This can take time – this is why you can be sick for
days/weeks.
3. Disposal
• Once the right antibody that fits the antigen is
found, they are mass produced and clump
onto the invading pathogen, marking it for
destruction.
• Killer T cells kill the body’s own cells that have
been invaded by pathogens, preventing the
pathogen from reproducing in the cell and
then infecting other cells.
4. Immunity
• Some antibodies remain for future use – you
usually cannot have the same disease twice!
3.2 Factors Affecting the Immune System
I. Vaccinations
• Vaccines are weakened pathogens given to
people to protect them from getting a disease.
• Vaccines stimulate your body to create
antibodies to destroy the pathogen.
• These antibodies will activate when the pathogen
enters the body again.
• Booster shots increase the antibody production
and extend the immune system’s memory for
that antigen.
II. Disorders of the Immune System
ALLERGIES:
• An allergy is an unusually high sensitivity to a
substance.
• Any substance that causes an allergic reaction is
called an allergen.
• Side effects of an allergic reaction are a result of
histamine. Histamine is a chemical that your
body releases when you need to fight invaders.
• Severe allergies can cause anaphylactic shock
(swelling, breathing difficulties, and sometimes
death).
III. AIDS/HIV
• Acquired Immunodeficiency Syndrome (AIDS) is an
infection of the immune system that leads to health
complications and often death.
• AIDS is cause by the human immunodeficiency virus
(HIV) that attacks the immune system by infecting
Helper T-cells.
• AIDS is transmitted by blood and semen.
• There’s no cure for HIV/AIDS, but a variety of
medications can be used in combination to
control the virus.
IV. Taking Care of your Immune System
• Eat a well-balanced diet
• Maintain personal hygiene (bathing, washing
hands, brushing teeth)
• Keep home clean
• Avoid tobacco and other non-prescription drugs
• Get plenty of rest and exercise
• Keep vaccinations up to date
• Do not engage in activities that involve sharing
body fluids with others.
3.3 Epidemics and Pandemics
• A disease is said to be endemic when it is at a
constant, “normal” occurrence within a given
geographical area. In this case, low numbers
of people become sick.
• A disease becomes an epidemic when it
affects an unusual number of people in a
community or region at the same time. A
higher number of people become sick.
Characteristics or an epidemic:
– When the # of people infected rises above
what is expected.
– Illness is specific to a certain area.
– Usually caused by circulation among people.
Examples of Epidemics:
• seasonal flu outbreaks happen each year
• Norovirus outbreaks have occurred on cruise
ships
• in 2003, the severe acute respiratory
syndrome (SARS) epidemic took the lives of
nearly 800 people worldwide
• in 2014, the Ebola virus resulted in 6070
deaths in West Africa
Pandemics
• A disease is a pandemic when it becomes
prevalent throughout an entire country,
continent, or the whole world.
• Thousands to millions of people become sick.
Characteristics of a pandemic:
•
•
•
•
Causes serious illness.
illness spreads easily from person.
is an outbreak of global proportions.
usually caused by a new form of a virus or
bacteria.
Examples of Pandemics:
• Spanish flu killed 40-50 million people in 1918
• The Franco-Prussian War triggered a smallpox
pandemic of 1870–1875 that claimed 500,000
lives
• HIV/AIDS
• In 2009, H1N1
How many people die from a
pandemic depends upon:
• The number of people who become infected
• The severity of disease caused by the virus (its
virulence)
• The vulnerability of affected populations
• The effectiveness of preventive steps
The World Health Organization (WHO) provides an
influenza pandemic alert system, with a scale ranging
from Phase 1 (a low risk of a flu pandemic) to Phase 6
(a full-blown pandemic):
• Phase 1: A virus in animals has caused no known infections in
humans.
• Phase 2: An animal flu virus has caused infection in humans.
• Phase 3: Sporadic cases or small clusters of disease occur in
humans. Human-to-human transmission, if any, is insufficient to
cause community-level outbreaks.
• Phase 4: The risk for a pandemic is greatly increased but not
certain.
• Phase 5: Spread of disease between humans is occurring in more
than one country of one WHO region.
• Phase 6: Community-level outbreaks are in at least one additional
country in a different WHO region from phase 5. A global pandemic
is under way.
How to prevent the spread of diseases?
• The best way to prevent a virus from
becoming a pandemic is to get a vaccination.
• Wash your hands often with soap and water.
If these are not available, use an alcoholbased hand cleaner or gel sanitizer. If using a
gel, rub your hands until they become dry.
• Avoid touching your mouth, nose,
or eyes with your hands unless you've just
washed your hands.
• When you cough or sneeze, cover
your mouth and nose with a tissue. Then
throw the tissue in the trash. Wash your
hands afterward.
• Avoid crowded places as much as you can and
stay home if you show signs of illness.
• Depending on the severity of the pandemic,
consider wearing a face mask if you must go into
a crowded area or be within 6 feet of others.
• Consider wearing a face mask if you must come
into close contact with an infected person.