Download 2.-Specific-Cellular

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
1. The Immune System b) specific cellular defences
By the end of this section you will
be able to …..
• describe what is meant by Immune
Surveillance
• describe what is meant by Clonal
Selection Theory
• describe the specificity of lymphocyte
receptors
What do these pictures have in
common?
Immune surveillance
• A range of white blood cell constantly
circulate and monitor the tissues.
• If tissues become damaged or invaded,
these cells release cytokines, which
increase blood flow resulting in specific
white blood cells accumulating at the
site of infection or tissue damage.
Lymphocytes
• Lymphocytes are
made in the bone
marrow from stem
cells.
• Some leave and
mature in the
thymus gland (Tlymphocytes)
• Whilst others
remain and mature
in the bone marrow
(B-lymphocytes)
Lymphocytes
• The body has a vast array of lymphocytes
and each with different SPECIFIC
functions.
• It is therefore important for the body to
create as many lymphocytes as possible
since a specific response is needed for
each type of infection!
• THINK/PAIR/SHARE: What do you think
we mean by a “clonal population of
lymphocytes”?
Clonal Selection
Theory
• https://www.yo
utube.com/watc
h?v=HUSDvSkn
IgI&feature=re
lated
Pool of lymphocytes showing a
variety of antigen receptors
Clonal
selection
theory
Clonal Selection Theory
• The body has a vast array of lymphocytes,
each with a single type of membrane
receptor specific for one antigen.
• When the receptor on a lymphocyte binds
to a non-self antigen, it becomes activated.
• This leads to the lymphocyte dividing
repeatedly and cloning themselves
• Thus, a clonal population of lymphocytes is
produced.
Clonal Selection Theory
Surface receptor
Y
antigen
Only B-Lymphocyte ____
is activated because the a_____
is complementary and specific
s_____ to cell Y receptor shape.
Clonal Selection Theory –
EXPONENTIAL GROWTH
What would you rather do?
1. work for a flat rate of £100 per week OR
2. start earning 1p but the salary doubles
each week.
• OPTION 1 – you make £5,200 per year.
• OPTION 2 – you make £5,242.88 after
only 20 weeks. After 52 weeks it becomes
an inconceivable amount of money.
Can you now ….
• describe what is
meant by Immune
Surveillance
• describe what is
meant by Clonal
Selection Theory
• describe the
specificity of
lymphocyte
receptors
Quick Questions
1. Describe when a clonal population of
lymphocytes would be produced in the
body?
2. If each lymphocyte can only recognise
one specific antigen, how is it possible
that lymphocytes offer effective
protection against a wide variety of
pathogens?
1. The Immune System b) specific cellular defences
By the end of this section you will
be able to …..
• describe the roles of 2 types of Tlymphocytes in response to infection
• describe the role of B-lymphocytes in
response to infection
Lymphocytes
• Lymphocytes respond specifically to:
– Antigens on foreign cells
– Cells infected by pathogens
– Toxins released by pathogens
• Collect 2
lymphocyte cards
• Work in pairs
• One person will
learn about BLymphocytes
• The other will learn
about TLymphocytes
• You will then teach
your partner about
your white blood cell
Your teaching should allow you and the other
pupil to be able to answer these questions…
B-Lymphocytes
T-Lymphocytes
• Explain the link between
B-lymphocytes and
antibodies
• What is special about
these antibodies?
• Describe the 2 effects of
an antigen-antibody
complex
• Explain the role of a
‘memory B cell’
• How many groups of Tlymphocytes are there?
• What are the names of
the 2 groups?
• Explain the link between
lymphocytes and apoptosis
• Explain the link between
lymphocytes and cytokines
• Explain how phagocytes
and B-lymphocytes are
involved
B-lymphocytes
B lymphocytes are able to recognise foreign
antigens and engulf them.
They then
display the
antigens on
their surface
waiting for a
TH cell to
release
cytokines and
activate it.
Some will become clone antibody-producing B
cells, others become cloned memory B cells
Activated B lymphocytes
Activated lymphocytes can produce a protein
specific to the antigen called antibodies.
The antibodies are able to bind to the
antigen creating an antigen-antibody
complex.
Antibody action
The binding of the antibodies causes the
• inactivation of the pathogen (or the toxin it
produces) and
• pathogen to become more susceptible to
phagocytosis
B-Lymphocytes
extra note
Antibody
receptor site
Antigen
A specific
antibody is made
by Blymphocytes.
Antibodies are
secreted into
the lymph and
blood where
they make their
way to the
infected area.
The antibodies
recognise a
specific antigen
surface.
Your teaching should allow you and the other
pupil to be able to answer these questions…
B-Lymphocytes
T-Lymphocytes
• Explain the link between
B-lymphocytes and
antibodies
• What is special about
these antibodies?
• Describe the 2 effects of
an antigen-antibody
complex
• Explain how role of a
‘memory B cell’
• How many groups of Tlymphocytes are there?
• What are the names of
the 2 groups?
• Explain the link between
lymphocytes and apoptosis
• Explain the link between
lymphocytes and cytokines
• Explain how phagocytes
and B-lymphocytes are
involved
T-lymphocytes
There are two different types of T-lymphocytes or
T-cells.
- cytotoxic T cells (TC cells) AKA Killer T cells
- helper T cells (TH cells)
• Cytotoxic T cells cause
apoptosis of an infected
cell (programmed cell
death)
• remember NK cells!
• Helper T cells become
activated when they have
come into contact with a
foreign antigen and produce
cytokines.
TH Cells
As seen before,
there is a vast pool
of different TH
cells with different
forms of antigen
receptors. One of
them will be
specific to the
antigen.
Helper T-lymphocytes (TH Cells)
ANOTHER way helper T cells can remove pathogens is when
phagocytes engulf the foreign cell
This phagocyte then presents the foreign antigen on its own
surface, meaning one of the TH cells will be able to bind with
it.
Antigen presenting cell
Helper T-Lymphocytes
extra notes
• When pathogens infect
a tissue, some
phagocytes capture the
pathogen and display
the it’s antigens on
their surface
• This display of antigen
presentation, activates
T-lymphocytes.
• Once one version of
the TH cell is activated,
it goes on to multiply
to give further clones
of activated TH cells
TC cells and cancer
TC cells are also able to recognise
antigens found on the surface of cancer
cells.
They are then able to bring about the
lysis of large cancer cells.
Antibody Production
• http://www.youtube.com/watch?v=lrYlZ
Jiuf18
• http://www.kscience.co.uk/animations/l
ymphocyte.htm
Can you now ….
• describe the roles
of 2 types of Tlymphocytes in
response to
infection
• describe the role of
B-lymphocytes in
response to
infection
Quick Questions
1. 2 types of lymphocytes are produced.
Explain the role of the lymphocyte
which is involved in cells selfdestructing.
2. What is produced by B-lymphocytes
during the immune response?
3. Name 3 possible effects of the protein
produced by B-lymphocytes
1. The Immune System b) specific cellular defences
By the end of this section you will
be able to …..
• describe what is meant by immunological
memory
• state the benefits of having memory
cells.
FROM PRIMARY TO
SECONDARY 
Primary response
• When a pathogen infects the body, it
takes time to raise an immune
response and select the correct T and B
cells (clonal selection) and produce
antibodies.
• This is called the primary response, and
very often it is too slow to prevent the
pathogen causing illness.
Secondary response
• However, if the person survives, and they come across
the SAME pathogen a second time, they will have a
much different secondary response!
• This is because the body has created MEMORY CELLS
• Some of the T and B lymphocytes that were
produced by clonal selection after the first
exposure survive long term as MEMORY CELLS.
• When the SAME foreign antigen is recognised by
these memory cells a second time, they very quickly
form many clones of both T cells and antibodyproducing B cells.
• This means that their are more antibodies produced
faster and for a longer duration.
• This is the secondary response.
Can you now ….
• describe what is
meant by
immunological
memory
• state the benefits
of having memory
cells.
Quick Questions
For each statement below state if it
refers to the 1st or 2nd exposure of a
pathogen
a) Larger concentration of antibodies produced
b) Clonal population of lymphocytes occurs
faster
c) Memory cells are produced
d) Immune response is longer
e) Illness occurs
1. The Immune System b) specific cellular defences
By the end of this section you will
be able to …..
• describe the role of T lymphocytes in
recognising self and non-self
• explain what is meant by an autoimmune
disease in relation to lymphocyte
regulation
• state what is meant by the term ‘allergy’
and give examples of common allergic
reactions
Decide if each card is
TRUE or FALSE
Crohns disease, type 1 diabetes,
Graves disease, psoriasis and
rheumatoid arthritis are examples of
autoimmune diseases.
Chicken pox, CJD, legionnaires’
disease and meningitis are examples
of autoimmune diseases.
An autoimmune disease is caused by
an overactive immune response in
which the body’s own cells are
destroyed.
Autoimmune diseases can be caught
from close contact with infected
people.
Treatment of autoimmune disease
only serves to alleviate the
symptoms, it does not cure the
disease.
Autoimmune diseases can be easily
cured with a combination of
antibiotics and anti-viral drugs.
There is no known prevention for
autoimmune disease.
Children can be vaccinated against
autoimmune diseases – this prevents
them from getting ill in later life.
Rheumatoid arthritis
In rheumatoid
arthritis,
cytokines cause
inflammation
which will
attack the bone
and cartilage in
joints, causing
them to be
replaced with
fibrous tissue
which leaves
the joint less
mobile than
before.
Type 1 diabetes
• Destruction
of Beta
cells
Graves disease
Psoriasis
skin condition that
causes red, flaky,
crusty patches of
skin covered with
silvery scales
Crohns diseases
Inflammation of the lining of
the digestive system (IBD)
Multiple
Sclerosis
Confusing self and non-self
• T-lymphocytes have specific surface proteins
that should be able to read the surface antigens
of a cell and tell if it is self or non-self.
• However, sometimes T-lymphocyte regulation can
fail
• T-lymphocytes fail to distinguish between the
surface proteins of the body’s own cells and
surface proteins on foreign cells and therefore
attacks body cells.
• The immune response against our own self cells is
called autoimmunity.
– Rheumatoid arthritis
– Type 1 diabetes
– Multiple sclerosis.
Confusing self and non-self
Allergies
B-lymphocytes sometimes over-react to
harmless substances like dust, pollen and
feathers etc. or even medicines such as
penicillin.
The hypersensitive B-lymphocytes release
antibodies which cause mast cells to release
histamine.
Some allergies are so severe that they can
trigger anaphylactic shock where the
histamine causes such a huge drop in blood
pressure it can be life threatening.
Can you now ….
• describe the role of T
lymphocytes in
recognising self and
non-self
• explain what is meant
by an autoimmune
disease in relation to
lymphocyte regulation
• state what is meant by
the term ‘allergy’ and
give examples of
common allergic
reactions
Questions – 12 minutes!
1)
2)
3)
4)
What are the two types of lymphocytes?
Where do T lymphocytes mature?
Why are cytokines released at the site of infection?
What is the name of the proteins found on cell surfaces that
trigger an immune response?
5) Describe clonal selection.
6) a) What is autoimmunity?
b) Give a condition linked to autoimmunity.
7) How does a TC cell lead to the destruction of an infected cell?
8) a) What does an activated B cell produce?
b) How do these molecules bring about destruction of a pathogen?
9) What term is used to describe the first infection of the body by a
pathogen?
10) If the body is re-infected at a later date, what is this known as?
11) Which cells are central to being able to fight off re-infection?
12) How does the immune response to the second infection compare to
the first?
Quick Questions
1. Choose the correct words from the
box below to describe what is meant by
the term allergic reaction
> Under-reacts
> Hyposensitive response
> Over-reacts
> Normally harmful substance
> Hypersensitive response > Normally harmless substance
2. What cell is involved in autoimmune
diseases?
3. Explain the role of this cell in
autoimmune diseases
BLOOD GROUPS
A, B, AB, O
Rhesus –ve and Rhesus +ve
Blood groups!
Agglutination
Agglutination
Tasks
• Stick in the blood group tables and
answer the following below it:
1. Explain why a person with blood
group A cannot receive a
transfusion from someone with
blood group AB
2. Explain why a person with Blood
group AB can receive a transfusion
from someone with blood group A
The Rhesus factor
• In addition to having A or B antigens, some
people have a further antigen on their
blood cells. This is called antigen D and
people who possess it are said to be rhesus
positive (+ve).
• Those that lack the antigen D marker are
said to be rhesus negative (-ve).
When does the rhesus marker
become a PROBLEM?
• Transfusion of Rh +ve
RBC to a Rh –ve person
must be avoided
• And a child born to
parents of different
rhesus factors may
also be at risk…
When does the rhesus marker
become a PROBLEM?
When does the rhesus marker
become a PROBLEM?
• The immune system of a Rh -ve recipient
would respond to Rh +ve red blood cells
and produce anti-D antibodies.
• These antibodies would persist leaving the
person sensitised.
• Any further transfusion of Rh +ve RBCs to
the Rh –ve recipient would result in the
person suffering from sever or fatal
agglutination.
How to test for your blood group
https://www.youtube.com/watch?v=mM1UNY6iWnA#t=101
You have now completed
Key Area 2 of Unit 4!
