Download lesson-4-antigeinc

Unit 4 Immunology and
Public Health
Unit 4 – Immunology and Public
Health
1. The Immune
System
a)Non-specific
defences
b)Specific cellular
defences
2. Infectious
Diseases and
immunity
a)Transmission and
control
b)Active
Immunisation and
Vaccination and
the evasion of
immune responses
2. Infectious Diseases & immunity
b) Active immunisation, vaccination and evasion
By the end of this section you will be
able to …..
• describe the process of antigenic
variation
• give examples of pathogens that use
antigenic variation
• describe why antigenic variation poses a
problem to public health
• Describe how to set up an experiment
to view the antibody-antigen interaction
(PS)
Evasion of specific immune
responses
• Not all diseases can be eradicated by
vaccines.
• Some pathogens have evolved
mechanisms that evade the immune
system and therefore vaccines are of no
or limited use.
• Pathogens can either:
1. Undergo antigenic variation
•
Malaria, Influenza, Trypanosomiasis (sleeping
sickness)
2. Directly attack the immune system
•
HIV and TB
Re-cap
• What is antigen?
• Describe the specific immune response
• Describe the role of memory cells
Let’s play Chinese Whispers!
Malaria
To prevent the red blood cells, which the malaria
protozoa hide in, from being destroyed they present
a protein on the cell’s surface which causes it to
stick to a blood vessel wall.
It is also able to
switch between many
genes for this
protein preventing
the immune system
producing
appropriate
antibodies in time.
Evolution of the FLU virus
• In this
diagram, the
antigens can
change in two
ways, but
importantly, it
means that the
antibodies
produced by
memory cells
cannot bind to
them and
inactivate the
pathogen.
Trypanosomiasis
• A protozoa called Trypanosoma
brucei causes the fatal disease
called trypanosomiasis or ‘sleepingsickness’.
• It has a glycoprotein coat which can
contain one of many different
antigens. About 1% of them can vary
the antigen and replace the whole
‘coat’ when the immune system
attacks.
• The new coat has different antigens
so the immune system has to start
again, giving it time to reproduce
before destroying another 99%.
Survive and
change
Survive and
change
Videos 
• Malaria:
http://www.youtube.com/watch?v=qvlTOhC
mxvY
• Trypanosomiasis:
• http://www.youtube.com/watch?v=4aVUrG
O97Zg&list=PLXfKWnjanUc3He0aOwo7Uw
0MuG0jlQjci
• Influenza:
• http://www.youtube.com/watch?v=ugM1nIhfIA
1. Antigenic variation
• Some pathogens can change their antigens,
avoiding the effect of immunological
memory.
• Antigenic variation occurs in diseases like
malaria and trypanosomiasis, and is one of
the reasons why they are still so common
in many parts of the world.
• Antigenic variation also occurs in the
influenza virus, explaining why it remains a
major public health problem and why atrisk individuals require to be vaccinated
every year.
Antibody and Antigen interaction
– using agar gel (Experiment)
• Agar gel can be used to observe
antibodies reacting with antigens.
• The agar allows the proteins to diffuse
towards each other
• When they meet they bind together.
This is indicated by a white line in the
agar.
Antibody and Antigen interaction
– using agar gel (Experiment)
Antigen X placed in
centre well
Blood plasma
of Pupil A
Blood plasma
of Pupil B
AIM: To observe the presence
of antibodies against antigen X
in various pupils
RESULTS
Blood
plasma
of
Pupil F
Blood
plasma of
Pupil E
Blood
plasma of
Pupil D
Blood
plasma of
Pupil C
• What conclusion can be drawn
from these results?
• Pupil C wanted to investigate
what other antibodies she had.
Explain how she could do this.
Antigen X placed in
centre well
Blood plasma
of Pupil A
Blood plasma
of Pupil B
Blood
plasma
of
Pupil F
Blood
plasma of
Pupil E
Blood
plasma of
Pupil D
Blood
plasma of
Pupil C
More
Questions!
• Antigen X is actually
from an Influenza virus
• All the pupils have
suffered from
influenza.
1. Explain why a line did
not form between ALL
the pupils and antigen
X.
2. Explain why a line DID
form between 3 of the
pupils and antigen X.
Antigen H placed in
centre well
Blood plasma
of Pupil A
Blood plasma
of Pupil B
Blood
plasma
of
Pupil F
Blood
plasma of
Pupil E
Blood
plasma of
Pupil D
Blood
plasma of
Pupil C
More
Questions!
• Antigen X was replaced
with an antigen from a
different virus (antigen
H).
• Only Pupils A and E
have been vaccinated
against this virus.
1. Predict the results
that would be observed
from this experiment.
Can you now ….
• describe the process of
antigenic variation
• give examples of
pathogens that use
antigenic variation
• describe why antigenic
variation poses a
problem to public health
• Describe how to set up
an experiment to view
the antibody-antigen
interaction (PS)