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BIOLOGY, M7 2025 HSC 28

Alpha-gal syndrome (AGS) is a tick-borne allergy to red meat caused by tick bites. Alpha-gal is a sugar molecule found in most mammals but not humans, and can also be found in the saliva of ticks. The diagram shows how a tick bite might cause a person to develop an allergic reaction to red meat.
 

 

  1. The flow chart shows the process of antibody production following exposure to alpha-gal. 
  2.   
  3. Describe the role of X, Y and Z in the process of antibody production.   (4 marks)

  4. An allergic reaction to alpha-gal sugar is similar to a secondary immune response.
    1.    
  5. Describe the features of antibody production shown in the graph.   (2 marks)

  6. Explain the role of memory cells in the immune response.   (3 marks)
Show Answers Only

a.    Antibody Production Process

  • X is a Helper T-cell that recognises the alpha-gal antigen presented by macrophages on MHC-II molecules.
  • Helper T-cells activate and coordinate the adaptive immune response through cytokine release.
  • Y is a B-cell that has receptors specific to the alpha-gal antigen.
  • B-cells are activated by Helper T-cells and undergo clonal expansion.
  • Some B-cells differentiate into memory cells for long-term immunity.
  • Z is a Plasma cell, which is a differentiated B-cell specialised for antibody production.
  • Plasma cells produce large quantities of antibodies specific to alpha-gal that circulate in the bloodstream.

b.    Features of Antibody Production

  • Initial tick bite produces low antibody concentration with slow, gradual increase over time, representing primary immune response.
  • Subsequent meat consumption triggers rapid elevation to higher antibody concentration, demonstrating secondary immune response with accelerated, amplified production.

c.    Role of Memory Cells

  • Memory cells are produced during primary exposure and remain in circulation for years, maintaining immunological memory.
  • Upon re-exposure, memory cells rapidly recognise the specific antigen, which triggers immediate clonal expansion.
  • This results in faster and stronger antibody production because memory cells bypass the initial activation phase. Hence, providing enhanced immune protection against subsequent infections.
Show Worked Solution

a.    Antibody Production Process

  • X is a Helper T-cell that recognises the alpha-gal antigen presented by macrophages on MHC-II molecules.
  • Helper T-cells activate and coordinate the adaptive immune response through cytokine release.
  • Y is a B-cell that has receptors specific to the alpha-gal antigen.
  • B-cells are activated by Helper T-cells and undergo clonal expansion.
  • Some B-cells differentiate into memory cells for long-term immunity.
  • Z is a Plasma cell, which is a differentiated B-cell specialised for antibody production.
  • Plasma cells produce large quantities of antibodies specific to alpha-gal that circulate in the bloodstream.

b.    Features of Antibody Production

  • Initial tick bite produces low antibody concentration with slow, gradual increase over time, representing primary immune response.
  • Subsequent meat consumption triggers rapid elevation to higher antibody concentration, demonstrating secondary immune response with accelerated, amplified production.

c.    Role of Memory Cells

  • Memory cells are produced during primary exposure and remain in circulation for years, maintaining immunological memory.
  • Upon re-exposure, memory cells rapidly recognise the specific antigen, which triggers immediate clonal expansion.
  • This results in faster and stronger antibody production because memory cells bypass the initial activation phase. Hence, providing enhanced immune protection against subsequent infections.

BIOLOGY, M7 2023 HSC 22b

Explain how antibodies are produced in response to the entry of a pathogen.  (4 marks)

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  • Antigens (foreign proteins) are detected by B cells as “non-self” foreign bodies.
  • Plasma B cells have associated antibodies with a specific shape that allows them to bind to antigens.
  • Once an antigen binds to the receptor of a B cell, it activates the B cell which replicates to form plasma cells.
  • These plasma cells produce an antibody that is specific to the antigen.
  • After the immune response, some B cells can remain dormant as memory cells, which can be activated upon recognition of the same antigen.
Show Worked Solution
  • Antigens (foreign proteins) are detected by B cells as “non-self” foreign bodies.
  • Plasma B cells have associated antibodies with a specific shape that allows them to bind to antigens.
  • Once an antigen binds to the receptor of a B cell, it activates the B cell which replicates to form plasma cells.
  • These plasma cells produce an antibody that is specific to the antigen.
  • After the immune response, some B cells can remain dormant as memory cells, which can be activated upon recognition of the same antigen.
♦ Mean mark 47%.

BIOLOGY, M7 SM-Bank 22

A summary of case-control studies conducted from 1997 to 2003 showed that a single dose of varicella (chickenpox) vaccine was 97% effective in the first year after vaccination and 86% effective in the second year. From the second to eighth year after vaccination, the vaccine's effectiveness remained stable at 81% to 86%. Most vaccinated children who developed chickenpox during the eight years after vaccination had a mild case of the disease.

Why do most vaccinated individuals, if they are infected, show only a mild case of the disease?  (2 marks)

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Answers should include two of the following reasons:

  • Virus enters and is detected.
  • Memory cells present.
  • Rapid antibody production where antibodies are produced in large numbers
  • Virus is neutralised
Show Worked Solution

Answers should include two of the following reasons:

  • Virus enters and is detected.
  • Memory cells present.
  • Rapid antibody production where antibodies are produced in large numbers
  • Virus is neutralised

BIOLOGY, M7 EQ-Bank 26

The immune system's primary role is to defend against pathogens. For this to be effective the immune system must be able to recognise cells that belong to the body and cells that do not.

  1. Describe the mechanism that the immune system uses to distinguish between body cells and potential pathogens. Support your answer with an example.   (3 marks)

  2. Explain why this mechanism means that patients who receive an organ donation require immune suppression drugs.   (3 marks)

Show Answers Only

a.    Immune system blood type mechanisms

  • Every cell has proteins on its surface which the body can use to distinguish them from self and non-self.
  • The body’s own cells produce a specific composition of surface proteins referred to as the major histocompatibility complex (MHC), as opposed to other proteins which are not recognised by the immune system and are called antigens.
  • This provides the basis of blood types, where A and B are specific surface proteins while O is blood with no surface proteins.
  • AB blood type individuals are therefore universal recipients, as their immune system has recognised both A and B proteins as self. This also explains why type O individuals are universal donors as their blood has no surface proteins, hence type O, A, B and AB individuals will not recognise it as foreign.
     

b.    Immune systems detect new donated organs as foreign bodies.

  • When foreign cells/material are detected by the body, an immune response will attempt to kill or remove it from the body.
  • The same scenario occurs during an organ transplant, as the donor’s MHC complex is different to that of the recipient.
  • To counteract this, specialists run genetic testing on donors as well as the recipient to find people with a similar chromosome 6 genetic sequence. MHC is coded by genes found on this chromosome and compatible organ donors are often family members.
  • As a precaution, specialists administer immune suppression drugs which will slow the patient’s immune response, reducing the chance of an attack on the donated organ.
Show Worked Solution

a.    Immune system blood type mechanisms

  • Every cell has proteins on its surface which the body can use to distinguish them from self and non-self.
  • The body’s own cells produce a specific composition of surface proteins referred to as the major histocompatibility complex (MHC), as opposed to other proteins which are not recognised by the immune system and are called antigens.
  • This provides the basis of blood types, where A and B are specific surface proteins while O is blood with no surface proteins.
  • AB blood type individuals are therefore universal recipients, as their immune system has recognised both A and B proteins as self. This also explains why type O individuals are universal donors as their blood has no surface proteins, hence type O, A, B and AB individuals will not recognise it as foreign. 

b.    Immune systems detect new donated organs as foreign bodies.

  • When foreign cells/material are detected by the body, an immune response will attempt to kill or remove it from the body.
  • The same scenario occurs during an organ transplant, as the donor’s MHC complex is different to that of the recipient.
  • To counteract this, specialists run genetic testing on donors as well as the recipient to find people with a similar chromosome 6 genetic sequence. MHC is coded by genes found on this chromosome and compatible organ donors are often family members.
  • As a precaution, specialists administer immune suppression drugs which will slow the patient’s immune response, reducing the chance of an attack on the donated organ.

BIOLOGY, M7 EQ-Bank 9 MC

Melanomas are characterised by uncontrolled cell division caused by mutations that continue to occur once the tumour has developed. Scientists have discovered that vaccines produced using antigens extracted from the patient's own melanoma cells can be useful in treating melanoma. When injected, the vaccines stimulate an immune response.

The effect of the melanoma vaccine is to stimulate

  1. T cells which produce antibodies.
  2. cytotoxic T cells which activate B cells.
  3. cell division to produce more lymphocytes.
  4. production of B cells which destroy melanoma cells.
Show Answers Only

`C`

Show Worked Solution
  • The vaccine will encourage the division of lymphocytes (B and T cells) as a response to melanoma antigens.

`=>C`

BIOLOGY, M7 EQ-Bank 7 MC

Melanomas are characterised by uncontrolled cell division caused by mutations that continue to occur once the tumour has developed. Scientists have discovered that vaccines produced using antigens extracted from the patient's own melanoma cells can be useful in treating melanoma. When injected, the vaccines stimulate an immune response.

What can be inferred from the scientists' discovery?

  1. Cancer cells carry unique antigens.
  2. Self-antigens are not present on cancer cells.
  3. The melanoma patient has a dysfunctional immune system.
  4. The body cannot mount an immune response against cancer cells.
Show Answers Only

`A`

Show Worked Solution
  • To provide a vaccine, there must be antigens present on cancer cells in order to trigger an immune response.

`=>A`

BIOLOGY, M7 EQ-Bank 4 MC

A student was vaccinated for rubella when they were 13 . Three years later, they were exposed to the active rubella virus.

Which graph best represents the student's production of antibodies over time?
 
 

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`D`

Show Worked Solution
  • When exposed to a pathogen for a second time, memory B cells can produce more antibodies in a shorter amount of time, providing the basis of immunity.
  • The initial exposure represents the vaccine, and second represents the exposure 3 years later.

`=>D`

BIOLOGY, M7 2014 HSC 17 MC

When B cells are activated they divide to form a large number of antibody-secreting cells.

How is this best explained?

  1. Mitosis and gene expression produce cytotoxic cells.
  2. Mitosis and differentiation produce B cells that repair tissues.
  3. Mitosis and cell specialisation produce cells that maintain health.
  4. Mitosis and differentiation produce cells for growth and development.
Show Answers Only

`C`

Show Worked Solution
  • Mitosis allows B cells to divide into identical plasma B cells.
  • Plasma B cells are specialised cells particular to one pathogen, allowing individuals to be protected against it.

`=>C`


♦ Mean mark 56%.

BIOLOGY, M7 2017 HSC 11 MC

A student was asked to complete a table showing whether T cells and B cells have particular characteristics.

Which row did the student complete correctly?

\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{B.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\
\end{array}
\begin{array}{|l|c|c|}
\hline
\rule{0pt}{2.5ex}\quad \quad \quad \quad \quad \quad \quad \quad \textit{Characteristic}\rule[-1ex]{0pt}{0pt}& \textit{T cell} & \textit{B cell}\\
\hline
\rule{0pt}{2.5ex}\text{Produces plasma cells}\rule[-1ex]{0pt}{0pt}&\checkmark&\checkmark\\
\hline
\rule{0pt}{2.5ex}\text{Produces antibodies that are released in body fluids}\rule[-1ex]{0pt}{0pt}& \checkmark&\textit{X}\\
\hline
\rule{0pt}{2.5ex}\text{Cell surface receptor can recognise a specific antigen}\rule[-1ex]{0pt}{0pt}& \checkmark&\checkmark\\
\hline
\rule{0pt}{2.5ex}\text{Forms clones once stimulated}\rule[-1ex]{0pt}{0pt}& \textit{X}&\checkmark\\
\hline
\end{array}
\end{align*}

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\(C\)

Show Worked Solution
  • T and B cell receptors can both recognise specific antigens.

\(\Rightarrow C\)


Mean mark 54%.

BIOLOGY, M7 2017 HSC 4 MC

What is the role of lymphocytes in the body?

  1. They fight infection.
  2. They initiate blood clotting.
  3. They transport oxygen around the body.
  4. They transport carbon dioxide around the body.
Show Answers Only

`A`

Show Worked Solution
  • Lymphocytes (B and T cells) protect the body from pathogens by coordinating the immune response.

`=>A`

BIOLOGY, M7 2016 HSC 24

Name an infectious disease and explain how ONE host response is a defence adaptation.   (3 marks)

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Exemplar solution:

  • A primary immune response is triggered when a person first contracts chicken pox – an infectious disease.
  • Activated B and T cells reproduce in large numbers to fight and destroy the pathogen.
  • The host survives.
  • Subsequent infection with the same pathogen results in an increased secondary immune response.
Show Worked Solution
  • A primary immune response is triggered when a person first contracts chicken pox – an infectious disease.
  • Activated B and T cells reproduce in large numbers to fight and destroy the pathogen.
  • The host survives.
  • Subsequent infection with the same pathogen results in an increased secondary immune response.

BIOLOGY, M7 2015 HSC 19-20 MC

Refer to the following information to answer Questions 19 and 20 .

The intestinal tract of a human foetus is sterile.
After birth, microflora from the mother are transferred to the baby's mouth through close contact. After a year, the microflora of the baby is similar to the mother's, with the baby's immune system ignoring these microbes.

Also during the first year of life, breast milk from the mother provides antibodies to the baby for any disease the mother has already experienced. When breastfeeding ceases, these antibody levels in the baby start to fall.

After the first year, any new species of invading bacteria is treated as a pathogen by the baby's immune system.

Question 19

A medical consequence for six-month-old babies that have only been bottle-fed with formula milk and not breastfed is that

  1. they will not develop microflora.
  2. their immune system will be damaged.
  3. their consumption of milk cannot be quantified.
  4. they will be at increased risk of infectious disease.

 
Question 20

Strict hygiene practices are followed in the care of newborns, whereas hygiene practices in the care of older babies are less emphasised.

Which of the following is the best reason for this difference?

  1. Vaccinations render personal hygiene unnecessary for older babies.
  2. Procaryotic cells are not identified as antigens in early development.
  3. Antibiotic treatments kill bacterial populations in the digestive system.
  4. Early exposure to pathogens helps to build a strong immune system.

 

Show Answers Only

Question 19: `D`

Question 20: `B`

Show Worked Solution

Question 19

  • Bottle fed babies will not have the added immunity that is provided by the mother’s breast milk.
  • They will therefore have immune systems that are more susceptible to infectious disease.

`=>D` 
 

Question 20

  • The immune systems of newborns will not work as efficiently as that of older babies as their immune systems are underdeveloped.

`=>B`


♦ Mean mark Q20 45%.

BIOLOGY, M7 2020 HSC 32c

Rabies is a disease that can affect all mammals and is caused by the rabies virus. It is transmitted by the bite of an infected animal. Without treatment it almost always results in death.
 
        

  1.  

The rabies virus is a single-stranded RNA virus. It contains and codes for only five proteins. The diagrams show the structure and reproduction of the virus.
 

 

Post exposure prophylaxis (PEP) is given to patients who have been bitten by a rabid animal.

PEP includes an injection of human rabies antibodies (HRIG) as well as injections of a rabies vaccine at 0, 3, 7 and 14 days after exposure to the virus.

The following graphs show a generalised response to rabies infection without and with PEP.
  

Explain how PEP prevents rabies developing after infection with the virus. Support your answer with reference to the information and data provided above.   (8 marks)

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Once the rabies virus has entered the wound:

  • It will use the patient’s cells to replicate and the viral concentration will increase (as seen in the first five days).
  • Without PEP the virus will continue to replicate, migrate to the CNS (in the first graph this occurs by day 7), and eventually cause rabies and death.
  • Initially, the infected individual will not have the antibodies required to inactivate the virus.
  • A HRIG injection provides the required antibodies to inactivate the virus, through inhibiting replication or enhancing phagocytosis. 
  •  The PEP graph shows that these antibodies will only last up to 21 days, but are essential in inactivating the initial virus, as seen by a reduction in viral concentration after 6-8 days. 

The rabies vaccine works by:

  • containing an inactivated or weakened version of the rabies virus, which stimulates an immune response by the individual.
  • Initially, macrophages will display an MHC-antigen complex on its surface which helper T lymphocytes will bind to.
  • This then stimulates specific plasma B cells which can produce complementary antibodies, and memory B cells, which stay dormant and can rapidly differentiate into plasma B cells when exposed to the same virus.
  • The PEP graph shows the rapid production of antibodies on day 7, which coincides with rapid decrease in the virus concentration over the next few days. 
  • The antibodies then remain in the bloodstream and slowly decline over months, which allows quick diffusion if the virus is encountered within that timeframe.
Show Worked Solution

Once the rabies virus has entered the wound:

  • It will use the patient’s cells to replicate and the viral concentration will increase (as seen in the first five days).
  • Without PEP the virus will continue to replicate, migrate to the CNS (in the first graph this occurs by day 7), and eventually cause rabies and death.
  • Initially, the infected individual will not have the antibodies required to inactivate the virus.
  • A HRIG injection provides the required antibodies to inactivate the virus, through inhibiting replication or enhancing phagocytosis. 
  •  The PEP graph shows that these antibodies will only last up to 21 days, but are essential in inactivating the initial virus, as seen by a reduction in viral concentration after 6-8 days. 

The rabies vaccine works by:

  • containing an inactivated or weakened version of the rabies virus, which stimulates an immune response by the individual.
  • Initially, macrophages will display an MHC-antigen complex on its surface which helper T lymphocytes will bind to.
  • This then stimulates specific plasma B cells which can produce complementary antibodies, and memory B cells, which stay dormant and can rapidly differentiate into plasma B cells when exposed to the same virus.
  • The PEP graph shows the rapid production of antibodies on day 7, which coincides with rapid decrease in the virus concentration over the next few days. 
  • The antibodies then remain in the bloodstream and slowly decline over months, which allows quick diffusion if the virus is encountered within that timeframe.

♦♦ Mean mark 41%.

BIOLOGY, M7 2021 HSC 28b

An mRNA vaccine has been developed in order to immunise people against a virus. The vaccine contains modified mRNA which codes for the spike protein on the surface of the virus.
 

Explain how this vaccine can lead to active immunity to the virus.   (5 marks)

Show Answers Only
  • The modified mRNA enters the individuals cells and is translated at the ribosomes to form the viral spike protein, which is then released into the body.
  • The protein will be rendered as an antigen, and will trigger a specific immune response by B and T lymphocytes that match the antigen.
  • Once the viral protein has been removed, memory B and T lymphocytes specific to the protein remain, providing active immunity that allows for a rapid future response.
  • If the individual is later exposed to the virus, the same spike proteins present on the virus’ surface will trigger a rapid and large response by the memory cells. This is the basis for providing active immunity.
Show Worked Solution
  • The modified mRNA enters the individuals cells and is translated at the ribosomes to form the viral spike protein, which is then released into the body.
  • The protein will be rendered as an antigen, and will trigger a specific immune response by B and T lymphocytes that match the antigen.
  • Once the viral protein has been removed, memory B and T lymphocytes specific to the protein remain, providing active immunity that allows for a rapid future response.
  • If the individual is later exposed to the virus, the same spike proteins present on the virus’ surface will trigger a rapid and large response by the memory cells. This is the basis for providing active immunity.

♦ Mean mark 43%.