Download Viruses and Immunity - Claremont Secondary School

The Immune System
&
Viral Specificity
Answer the following questions using your textbook:
Miller & Levine p. 969 -972 or Nelson p. 201 – 204.
1.
2.
3.
What is a pathogen?
Name the system that defends the body against pathogens?
Explain the non-specific response and the specific response of
the body.
4. COPY: Primary line of defense = skin mucous, membranes,
tears, digestive enzymes non – specific response
Secondary line of defense=phagocytic white blood cells (engulf
foreign bodies (viruses, bacteria..) non-specific response
Tertiary line of defense = lymphocytes – white blood cells that
produce antibodies (active immunity)specific response
5. What are interferons?
6. A) What is an antigen?
B) What is an antibody?
A pathogen is
anything that causes a
disease
The immune system is
our bodies’ way of
defending itself
against pathogens.
The immune system can be
divided into 2 parts:
Non-specific response = body’s
first line of defense against
disease. Tries to prevent you
from getting sick in the first
place.
Specific response = if pathogen
gets by 1st line of defense.
= there are specific
antibodies made that will
recognize a virus & prevent it
from infecting the host.
There are 3 lines of defense:
Primary line of defense (physical) =
skin mucous, membranes, tears,
digestive enzymes non – specific
response
Secondary line of
defense=phagocytic white blood
cells (engulf foreign bodies
(viruses, bacteria..) non-specific
response
Tertiary line of defense =
lymphocytes – white blood cells
that produce antibodies (active
immunity) specific response
Innate---Interferons
Small proteins produced by
cells when they are
infected with a virus,
that help other cells
resist viral infection
(when released from a
virus infected cell).
They seem to make it more
difficult for the virus to
infect other cells –
“interferes” with a virus
Acquired Specific Immune Responses
Antigen = A protein that stimulates the production of
antibodies. These proteins are on the invader /
foreign body & identify it as foreign. Found on
surface of pathogen
Antibody = Proteins in the blood that react with
antigens – flag the pathogen for destruction by a
white blood cell
Viral Specificity
• A virus infects a specific host:
only plants, only animals, only
fungus or only bacteria.
• Some are very specific in that
they infect a particular
species such as only humans,
only peach tree etc…
• As well, viruses may infect
only specific cells of the body
Ex. Influenza infects lung cells
So what can we do?
Vaccines: We infect ourselves with a
“deactivated” virus so that our immune system
can produce antibodies and be ready in case of
the real thing.
Host Range: the number of different species a
virus can infect
• Narrow host range =
infects only 1-3 species.
– Ex. Human cold virus
• Broad host range =
infects many different
species
– Ex. Rabies – infects
mammals & birds
• A virus identifies the
host cell by a “lock &
key” system.
– Antigens on the outside
of the virus fit into a
specific receptor site on
the host cell’s surface.
AIDS
•HIV can be
transmitted sexually,
through contact with
contaminated blood,
tissue, or needles,
and from mother to
child during birth or
breast-feeding.
•Full-blown symptoms
of AIDS may not
develop for more than
10 years after
infection.
CHICKEN POX
•Infects most children worldwide by
the age of 10.
•Transmitted in airborne droplets
exhaled from an infected person.
•The virus causes a low fever and a
rash of fluid-filled blisters that begin
as red spots covering most of the
body and the inside of the mouth.
•The disease is dangerous to newborns, to
people first infected in adulthood, and to those
in whom the virus remains dormant in nerve
cells, erupting as the more painful and
sometimes chronic (shingles) later in life.
Hepatitis B
•The hepatitis B virus
(HBV) causes
inflammation of the
liver.
•Symptoms of hepatitis
B infection include
jaundice and a flu-like
illness
•Chronic infection can
lead to serious
problems such as
cirrhosis and cancer of
the liver.
•The rabies virus is usually
RABIES
transmitted to humans by a bite from
an infected dog, but the bite of any
animal (wild or domestic) is suspect in
an area where rabies is present.
•In North America, skunks are the
principal carriers of the disease,
although the raccoon and bat
populations are also affected.
•Symptoms of the disease appear
after an incubation period of ten
days to one year and include fever,
breathing difficulties, muscle
spasms, and in later stages, an
irrational fear of water.
• Death almost invariably occurs within 3 days
to 3 weeks of the onset of symptoms.
PAPILLOMAVIRUS (HPV)
•This virus can also cause
benign skin tumours.
•FACT: Females that
have sexual intercourse
before they are 19 are
more likely to get this
virus.
•FACT: Females with
this virus are more
likely to contract
cervical cancer.
•FACT: Sexually
promiscuous teenagers
are more likely to get
cervical cancer!
HERPES
•Herpes (Greek for “to creep”), is applied
to several types of skin eruptions
characterized by formation of blisters.
•Some herpes viruses cause
mononucleosis and can lead to birth
defects when the virus invades pregnant
women.
•Together, these viruses are estimated to
cause more human illnesses than any other
group of viruses.
JUNGLE FEVER
A severe form of malaria
common in tropical
regions, especially
Southeast Asia
EBOLA
•About one week after
infection, the virus begins
attacking blood and liver
cells (1).
•As the disease swiftly
progresses, the virus
may destroy vital organs
such as the liver and
kidneys (2).
•This leads to massive internal bleeding (3). Shock and respiratory
arrest soon follow, then death.
SMALLPOX
• Once greatly
feared for its ability
to kill or disable its
victims, smallpox
was eradicated by
1979 through a
worldwide
vaccination
campaign.
• Some fear that it
may be used as a
biological weapon