Download 2.2.2 Immunity taught session

Immunity
A recap
What protects the body from
disease?
What are the differences between internal and external defences?
What are they?
White blood cells
PHAGOCYTE – neutrophils
and monocytes
Multi-lobed nuclei
Produced in bone marrow
LYMPHOCYTE – T and B
Single nucleus
Produced in bone marrow and
matured in Thymus gland or
Bone Marrow.
Phagocytosis
• This is a generalised immune response
and results in large particles being
engulfed and digested by phagocytes.
• The phagocyte is attracted to the
bacterium by proteins and chemicals
that the bacteria itself releases.
• It engulfs and then digests it.
General or Specific
• Phagocytosis is a fairly general reaction
to the invasion of any pathogen.
• This is a very useful ‘first’ defence but
to be truly effective against disease we
need to be able to have completely
specific responses to specific antigens.
• This is provided by antibodies
Antibodies
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Made from protein
Also known as immunoglobulins (Ig)
Synthesised by B-lymphocytes
They are entirely specific to one
antigen (a bit like the active site of an
enzyme)
Structure
• The constant
region of the
antibody remains
the same in all.
The variable region
is antigen specific.
• There are two
binding sites on
each antibody
• They can change
shape by moving at
the hinge region
How do they work?
1) Agglutination
By sticking to more than one antigen the
antibodies are able to make the
pathogens clump together. This makes
it possible for phagocytes to attack
them.
2) Neutralisation
Antibodies bind to the toxins released by
the pathogen neutralising their effect.
Self and Non-self
• If antibodies recognised the body as
non-self there would be a big problem.
• In the developing foetus any antibody
that is made that fits a ‘self’ marker is
destroyed. As a result the only ones
left are those suitable for pathogens.
Immunity
• There are different classes of immunity:
ACTIVE
PASSIVE
And
NATURAL
ARTIFICIAL
What do you think these are, how can you
get them? (DON’T LOOK IN YOUR
BOOKS!)
Natural Immunity
• Either inherited – eg from mother
during pregnancy or through breast
feeding
• Or through actually getting the disease
yourself
Artificial Immunity
• Result of deliberate exposure to the
antigen – eg through vaccination
Passive Immunity
• Where antibodies are introduced to the
body. This is shortlived as no memory
cells are made.
Active Immunity
• Results in memory cells being formed –
this is usually long-lasting.
Vaccination
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How does this work?
What are the risks?
What are the benefits?
If you were going to initiate a
vaccination programme what
considerations would you need to take?
Different types of vaccine
• Living attenuated micro-organism
This is where the pathogen is injected but it
is a weakened form. Eg measles, TB, polio
• Dead micro-organism
The pathogen is harmless but the antigens
can induce immunity. Eg Typhoid, cholera,
whooping cough
• Genetically engineered micro-organism
The antigen producing gene from the
pathogen is transferred to a harmless
bacterium. The body responds to the
antigens without risk. Eg Hepatitis B
Your task
You are going to make a table summarising the 4
different types of immunity. Include what it is,
how you get it and an example. Make sure you
include plenty of detail, especially with the
natural passive immunity in terms of it’s link
with immunity for babies.
Natural
Passive
Active
Artificial
Control of Disease
• Vaccination controls infectious diseases.
• For a population to gain immunity to a
disease a certain percentage of the
population needs to be immune – once that
percentage is reached the population can
benefit from herd immunity.
• The percentage required will vary from
disease to disease and from population to
population.
• However, it is not always as simple as that!
Vaccination programmes
You have been charged with the task of
eliminating ‘skivalitis’, a highly
contagious disease, from the population.
What are you going to be looking for in
your vaccine to ensure that you can
immunise the entire population?
You will need:
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A suitable vaccine
Few side effects
Easy storage, delivery etc..
People to administer the vaccine
The ability to administer the majority
of the population.
Your task
• You need to draw a series of annotated
diagrams to illustrate:
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Phagocytosis
Antibody action
Humoural immunity
Cell-mediated immunity