14.1
Week 14
Disorders of Immune
Responses
Area of Study 2
Detecting and Responding
Key knowledge
 Autoimmunity
 Hypersensitivity
 Allergens and allergic responses.
Key skills
 Investigate and inquire scientifically
 Apply biological understandings
 Communicate biological information and understanding.
Tasks this week relate to Outcome 2.
 Describe and explain coordination and regulation of an organism’s
immune responses to antigens at the molecular level.
Relevant websites – See online biology course environment. Go to the
Links section.
Use the Quizlet site to make your own list of the
terms used in week 13 and 14. Share the link with
your fellow classmates at the Biology Ning.
http://quizlet.com/
14.2
The Objectives
By the end of this week you should:



understand what an autoimmune disease is
understand the cause of allergic responses
have summarised some of the earlier work.
Read carefully through this Week’s work before completing the tasks.
Review Some Main Points
Defence mechanisms
Animals and plants have mechanisms with which they defend themselves
against organisms that cause disease. All organisms are able to recognise
their own cells as distinct from the cells of other species i.e. they are able
to distinguish between ‘self’ and ‘non-self’.
Immunity
Your body is being continually attacked by disease-causing pathogens
(parasites). How does your body defend itself?
There are two lines of defence:


Non-specific defence – general protection against pathogens
Specific defence – specific immunity.
Specific immunity – B cells
B cells are formed in the bone marrow. Known as the third line of defence
this involves a specific response to a particular infection (microorganism) by the immune system. This immunity is retained – acquired
immunity.
Specific immunity – T cells
T cells are also part of the third line of defence. Lymphocytes (white
blood cells) differentiate into mature T cells in the thymus, whilst they do
not produce antibodies they play a number of important roles. One of
them involves the destruction of body cells that have been infected by a
virus. Immunity involving T cells and phagocytes is called cellular
immunity.
Acquiring specific immunity
Antibodies are made in response to contact with a disease causing
organism. These antibodies are specific and so the person is resistant to
further infection by that organism. This is called specific immunity. There
are three words often associated with specific immunity:



acquired immunity is when antibodies are acquired
passive immunity is when antibodies are acquired from an outside
source
active immunity is when the antibodies are produced within the
person.
14.3
Rhesus incompatibility
The antibodies against the Rh antigen are not normally preset in blood
plasma, but Rh negative individuals recognise Rh factor as ‘foreign”.
Problems arise during some pregnancies (Figure 14.1). If an Rh negative
mother is carrying an Rh positive child, some of the baby’s blood cells
may cross into the mother’s bloodstream, particularly during childbirth. If
this happens, the mother will begin to produce antibodies to the Rh factor.
If this sensitised mother becomes pregnant again with an Rh positive
child, the leakage of only a few red blood cells through the placenta will
trigger a rapid production of antibodies. Rh antibodies that pass through
the placenta into the baby agglutinate the baby’s blood, causing severe
anaemia. This often requires transfusion of the baby’s blood after it is
born, or sometimes transfusion while the baby is still in the uterus. The
severity of the hypersensitisation of the mother increases with each
successive problem pregnancy.
Figure 14.1
When an Rh negative mother
is pregnant with an Rh
positive baby, the mother may
become sensitised to the Rh
antigen. This can cause
problems in a later pregnancy
with an Rh positive baby.
Diagram courtesy of
Heinemann Biology Two, 4th
Edition.
These days the blood group of a mother is always determined. If she is Rh
negative the blood group of the baby will also be tested. If the baby is Rh
14.4
positive, the mother will be given an injection of Rh antibodies (i.e.
passive immunity, see page 194) shortly after giving birth. These
antibodies bring about the destruction of any foetal blood cells that may
have passed into her blood before they have time to trigger her immune
system into producing Rh antibodies. To prevent hypersensitisation of the
mother, this procedure must be carried out each time an Rh negative
mother bears an Rh positive child.
Other adverse events associated with immunity
Along with Rhesus incompatibility: auto-immune disease, rejection of
transplant organs and immune deficiency diseases like AIDS and allergies
are all examples where our immune system does not operate to our
advantage.
Allergen – a substance that causes an allergic response. The body
produces the antibody IgE (immunoglobulin type E) against allergens
such as dust. Pollen and plant spores.
Read through pages 195 to 197 of your textbook and complete the tasks or
questions that follow.
Review Questions – Answers at the end of the week
Questions
1. Describe and explain the cause of allergic responses.
2. Explain, with reference to a particular example, what an autoimmune
disease is.
3. A characteristic in people with SCID is the lack of the enzyme
adenosine deaminase. Under normal conditions, this enzyme breaks
down the amino acid adenosine. Accumulated adenosine in
lymphocytes proves toxic to those cells. Explain why the immune
system of a person with SCID is impaired.
Read through the following revision exercise. Complete the sentences and then
correct your answers. Include a reflection of this task in your personal
reflection for week 14.
14.5
Self Corrected – Answers at the end of this week
REVISION
Complete the following question for revision. The answers are at the end
of the week. Complete a personal reflection of these questions online.
Immunity
Questions
1. The major histocompatibility complex (MHC) is ________________
________________________________________________________
________________________________________________________
2. ‘self’ means ______________________________________________
3. One way in which a non-specific immune response differs from a
specific response is ________________________________________
________________________________________________________
________________________________________________________
4. An example of the first line of defence of the body against infection is
________________________________________________________
________________________________________________________
5. Two kinds of cells which form part of the second line of defence of
the body are ________________ and _______________________.
6. Lymph contains __________________________________________
________________________________________________________
________________________________________________________
7. Three tissues or organs that are part of the lymphatic system are :
________________________________________________________
________________________________________________________
________________________________________________________
8. Complement protein is _____________________________________
and as part of the second line of defence it ______________________
________________________________________________________
________________________________________________________
9. Interferon is _____________________________________________
and as part of the second line of defence it _____________________
Specific immunity – B cells
10. The two main types of lymphocytes associated with immunity are
a) _________________which mature in ______________________
b) _________________which mature in ______________________
14.6
11. Protein markers on foreign cells are also know as ________________
________________________________________________________
12. Immunoglobulins are also knows as ___________________________
________________________________________________________
13. The cells formed by the cloning of B cells are _________________
and their function is _______________________________________
________________________________________________________
14. The cloning of B cells is important in the immune response because
________________________________________________________
15. The main features of the primary antibody response are ___________
________________________________________________________
________________________________________________________
16. Give the differences between primary and secondary antibody
response in the table below.
Primary antibody response
Secondary antibody response
Specific immunity – T cells
17. Immunity involving T cells is called cellular immunity because
___________________________________________________
___________________________________________________
18. Having recovered from tuberculosis five years ago a child will be
immune to the disease for the following reasons:
____________________________________________________
____________________________________________________
19. Give the differences between specific and non-specific immunity
in the table below.
Specific immunity
Non-specific immunity
14.7
20. One method of making antivenoms(also known as antivenenes) is
to:
____________________________________________________
____________________________________________________
(You may need to read through page 186 of your text book again.)
Adverse events associated with immunity
21. Antihistamines are used on allergy sufferers for the following
reasons:
____________________________________________________
____________________________________________________
22. The purpose of the immunoglobulin injection given to some
women just before birth of a child is _______________________
____________________________________________________
____________________________________________________
23. People with AIDS are particularly susceptible to a range of
infections because ______________________________________
____________________________________________________
____________________________________________________
24. A baby is born with a defective thymus. Its ability to resist
infection at birth will be ____________________and at 6 months
of age it will be ___________________________________
Plant defences
See page 164 of your text book.
25. Plants also have a first and second line of defence. Give one
mechanism for each.
A first line of defence mechanism in plants is ___________________
________________________________________________________
________________________________________________________
A second line of defence mechanism in plants is _________________
________________________________________________________
________________________________________________________
Optional Revision Activities
Use the CD-Rom that came with your text book for this work. Go
to the section titled Chapter 6.
Have a go at the:
‘Match Up’ exercise and the ‘Self test’.
View the ‘Immune Response” animation.
14.8
Challenging Activity: Mnemonic Activity
Choose one or more terms from the list given on page 199 of your
textbook and create a memory aid to help you remember the definition of
that term. You may use drawings, poetry, song, sound, whatever works
for you! Share your ‘mnemonic’ (memory aid) with the other students of
your class via the chat room. Feel free to discuss your ideas with me. Use
the glossary found on page 388 for definitions of terms.
Log on to the www.decvonline.vic.edu.au check out the back of your
DECV book for your login details if you have forgotten.
Click on the link to the Unit 3 Biology course.
Click on the button “Discussion Room”
Place your Mnemonic as a comment to the Discussion post titled
Mnemonics Week 14.
Challenging Activity: Personal Reflection
Log on to the VCE Biology Course. Place your Personal Reflection in the
Biology Blog as outlined on 0.7 in the introduction of this book.
Exam Practice Exercise
Past Exam Questions
Each week you will get at least one question which relates to the weeks
work, which comes from a past VCE exam paper.
The purpose of this task is to familiarize yourself with the type of
questions you will encounter during the exam and the timing you should
devote to each.
Timing
You should allow 1 minute and ten seconds per mark assigned to the
question.
1. [Q7, 2003]
Blood is grouped according to the kinds of antigens on the surface of
red blood cells of an individual.
One blood group in humans is the Rhesus blood group. With regard to
this group, individuals are classified as follows:
Rhesus positive
Rhesus negative
Individuals that have Rhesus protein on red
blood cells (rbc)
Individuals with no Rhesus protein on red
blood cells
14.9
Under normal conditions, no Rhesus antibodies exist in blood plasma
but Rhesus antibodies can be produced in particular circumstances. In
an emergency, a male who is Rhesus negative may be given a
transfusion.
A male, blood group Rhesus negative, unexpectedly lost a lot of blood
during a minor operation and urgently needed a blood transfusion. No
suitable Rhesus negative blood was available and he was given a
transfusion of Rhesus positive blood. The man’s blood was monitored
over time.
Consider the following symbol code and answer part a.
structure 1
structure 2
structure 3
Rhesus – ve rbc
Rhesus +ve rbc
Rhesus antibody
Figure 11.3
a. In the following table, list which of the structures, 1, 2 and 3, you
would expect to find in the man’s blood at each of the times indicated.
Prior to
operation
One day after
transfusion
One month after
transfusion
One year after
transfusion
Table 11.1
4 marks
b. Explain why you gave the particular answer you did for the box ‘one
month after transfusion’ in part a.
2 marks
The man had an accident about five years after his minor operation and
again required a blood transfusion. A doctor examined the man’s medical
history and commented ‘Well we certainly cannot give him Rhesus
positive blood this time’.
c. Explain whether you agree or disagree with the doctor’s comment
regarding a Rhesus positive blood transfusion.
2 marks
[Total 8 marks]
14.10
Checklist
This week you should have sent this work to me.
Please tick the items you have sent, and keep this as your record:

At least one mnemonic of a biological term left online

Your personal reflection of week 14
Don’t forget to drink plenty of water!
Feedback
What if anything needs to be improved, corrected, cleared up or presented
better from the materials presented in this week?
Answers to Past Exam Questions
Q1 [Q7, 2003]
a.
Prior to operation
Structure 1
b.
One day after
transfusion
Structure 1
Structure 2
One month
after transfusion
Structure 1
(Structure 2)
Structure 3
One year after
transfusion
Structure 1
Structure 3
If only structure 1 and 3.
Structure 1 is present because the man will be continually replacing
his dead red blood cells with new similar red blood cells.
Structure 3 is present because when structure 2 was introduced to the
body the man’s immune response would have been activated to
produce specific B plasma cells which in turn produce rhesus
antibodies.
If structure 2 is included then these cells would not have died from
the original transfusion.
d. Agree. Memory cells would have been produced after the first
transfusion. These cells would quickly divide to produce more
memory cells and plasma cells after another transfusion. In this way
many rhesus antibodies would be produced and these would result in
blood clotting and possible death of the patient.
14.11
Answers for questions on page 14.4 to 14.7
1.
2.
3.
Allergies are an exaggerated immune response to the antigens of normally harmless
substances. Symptoms include itchy eyes, sneezing, runny nose, skin rashes and difficulty
breathing, and are caused by inflammation and excessive mucus production in those areas
exposed to the antigen.
An autoimmune disease occurs when an individual’s immune system attacks tissues of the
individual. For example, in rheumatoid arthritis the B and T cells attack collagen tissues
around
the joints.
If adenosine is allowed to build up in a person with SCID it will kill the lymphocytes, the
cells
of the immune system, and hence destroy the immune system of that individual.
Revision
1. The major histocompatibility complex (MHC) is a cluster of genes that allows Tlymphocytes to discriminate self from non-self.
2. Self means material made by the body’s cells. Non-self means foreign material such as
snake venom, dust, pollen viruses and micro-organisms.
3. One way in which a non-specific immune response differs from a specific response is
Non specific response
React in the same way to all infection
Have no memory about prior infections
Level of response same for each infection of
the same organism
Specific response
React in a specific way to each infection
Have a memory about prior infections
Much greater response on a second infection
by the same organism.
4. An example of the first line of defence of the body against infection is the skin which acts
as a barrier against entry by micro-organisms (or mucous membrane, natural secretions,
or natural flora).
5. Two kinds of cells that form part of the second line of defence of the body are Phagocytes
and killer cells.
6. Lymph contains memory T and B cells
7. Three lymphoid tissues or organs include the spleen, thymus and lymph nodes.
8. Complement protein is a blood protein and as part of the second line of defence it
destroys the membranes of invading micro-organism or sticks to invading microorganism that then become more readily identifiable as foreign to phagocytes.
9. Interferon is another group of proteins and as a part of the second line of defence it acts
on uninfected cells making them more resistant to the virus.
10. The two main types of cells associated with immunity are
a) B cells which mature in the bone marrow.
b) T cells which mature in the thymus gland.
11. Protein markers on foreign cells are also known as antigens.
14.12
12. Immunoglobulin is a protein that identifies antigens and it is found on the surface of B
cells.
13. The cells formed by the cloning of B cells are plasma cells and their function is producing
the same kind of antibody.
14. The cloning of B cells is important in the immune response because they produce large
amount of antibodies and B memory cells which can survive for several years.
15. The main features of the primary antibody response are production of low level
antibodies about 10 days after infection.
16.
Primary antibody response
Low level of antibodies produced
Very slow. Requires clonal expansion.
Less effective than secondary response.
Secondary antibody response
High level of antibodies produced
Much quicker because there is no need for
clonal expansion
Higher amount of antibodies for a long time
after a second infection
17. Immunity involving T cells is called cellular immunity because the T cells don’t produce
antibodies but do react with other cells in the immune response.
18. Having recovered from tuberculosis five years ago a child will be immune to the disease
for the following reasons:
 antibodies produced in response to exposure to the particular antigen
 B memory cells and T cells produced that react quickly if another encounter occurs
with the same antigen.
19.
Specific immunity
Non-specific immunity
Has a memory of a prior infection
Has no memory of a prior infection
Involves production of antibodies and
Not affected by prior contact with a particular
specialised cells
micro-organism.
Involves acquired immunity
Involved many physical barriers and chemical
barriers
Involves natural immunity
20. One method of making vaccines or antivenoms involves a very small dose of venom
being injected into a rabbit to produce the antivenom. Then the antivenom is extracted
from the rabbit’s blood.
21. Antihistamines are used on allergy sufferers for the following reasons because they
reduce the allergic response such as swelling, inflammation.
22. The purpose of the immunoglobulin injection given to some woman after the birth of a
child is to react with and remove any foetal blood cells from the mother’s circulatory
system. This prevents the development of any memory cells which could attack Rhesus
+ve foetal blood cells during a next pregnancy.
14.13
23. People with AIDS are particularly susceptible to a range of infections because HIV
destroys a key component of the immune system - T helper cells whose action include
stimulating B cells to produce specific antibodies.
24. A baby is born with a defective thymus. Its ability to resist infection at birth will be quite
normal, because of the antibodies gained from the mother. And at 6 months of age it will
be greatly reduced as T cells will not be able to grow to maturity.
25. Plants also have a first and second line of defence. Give one mechanism for each.
A first line of defence mechanism in plants is the waxy layer they have on their leaves,
bark and thorns or hairs.
A second line of defence mechanism in plants is resin and enzymes such as phytoalexins.
END OF WEEK 14
14.14
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14.15
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