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BIOLOGY, M7 2024 HSC 32

Helicobacter pylori is a bacterium that invades the gut lining and can cause damage to the stomach as shown in the diagram.
 

With reference to innate and adaptive immunity, explain how the body responds after exposure to Helicobacter pylori.   (7 marks)

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→ Damaged cells release chemicals that trigger inflammation as an initial response.

→ The inflammatory response causes blood vessels to dilate, increasing blood flow and allowing phagocytes (macrophages and neutrophils) to move into the infected area.

→ Phagocytes process H.pylori antigens and present them to helper T-cells, which launch the adaptive immune response by releasing cytokines.

→ This cytokine release activates both T and B cells to mount multiple specific defences.

→ Cytotoxic T-cells directly attack H.pylori while memory T-cells remain for secondary rapid responses.

→ Suppressor T-cells regulate the immune response and plasma B-cells produce H.pylori-specific antibodies. Memory B-cells persist for responding to future (secondary) infections.

→ Antibodies work in two ways – direct neutralisation of antigens and tagging antigens for destruction by phagocytes.
 

The immune response involves both innate and adaptive immunity systems working together:

→ Innate immunity provides rapid, immediate defence.

→ Adaptive immunity develops more slowly but offers long-term protection through memory cells.

Show Worked Solution

→ Damaged cells release chemicals that trigger inflammation as an initial response.

→ The inflammatory response causes blood vessels to dilate, increasing blood flow and allowing phagocytes (macrophages and neutrophils) to move into the infected area.

→ Phagocytes process H.pylori antigens and present them to helper T-cells, which launch the adaptive immune response by releasing cytokines.

→ This cytokine release activates both T and B cells to mount multiple specific defences.

→ Cytotoxic T-cells directly attack H.pylori while memory T-cells remain for secondary rapid responses.

→ Suppressor T-cells regulate the immune response and plasma B-cells produce H.pylori-specific antibodies. Memory B-cells persist for responding to future (secondary) infections.

→ Antibodies work in two ways – direct neutralisation of antigens and tagging antigens for destruction by phagocytes.

♦♦ Mean mark 48%.

The immune response involves both innate and adaptive immunity systems working together:

→ Innate immunity provides rapid, immediate defence.

→ Adaptive immunity develops more slowly but offers long-term protection through memory cells.

BIOLOGY, M7 2020 VCE 35 MC

Monoclonal antibodies attaching to antigens on a cancer cell are shown in the diagram below.
 

Monoclonal antibodies

  1. are used to suppress B cells acting on cancer cells.
  2. make it easier for cells of the immune system to detect cancer cells.
  3. can bind to dendritic cells to stimulate them to destroy cancer cells.
  4. can attach to many structurally different proteins found on the surface of cancer cells.
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\(B\)

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→ Monoclonal antibodies bind to proteins on the surface of cancer cells, marking them for detection and destruction by the immune system.

→ By making the cancer cells more visible to the immune system, the monoclonal antibodies facilitate the immune system’s ability to recognise and attack the cancer cells.

\(\Rightarrow B\)

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 SM-Bank 27

Influenza is an infectious respiratory disease. In humans, it can be caused by the influenza A or influenza B viruses.

Antigenic drift can result in small changes to the structure of the antigens on the surface of the influenza virus, as shown in the diagram below.
 

  1. What change would have occurred within the virus to bring about the change in the structure of the antigen?  (1 mark)

  2. Vaccines against influenza are available and it is recommended that people are vaccinated each year.
  3. Explain, in terms of antigenic drift, why vaccinations are recommended yearly for influenza rather than once every few years.  (2 marks)

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a.   Mutation.

b.   Correct answers could include:

→ Vaccines contain new antigens resulting in the production of new antibodies OR memory cells specific to the antigen.

→ Memory cells allow for a faster OR larger immune response.

→ Any existing memory cells specific to the previous antigens would no longer be effective.

Show Worked Solution

a.   Mutation.

b.   Correct answers could include:

→ Vaccines contain new antigens resulting in the production of new antibodies OR memory cells specific to the antigen.

→ Memory cells allow for a faster OR larger immune response.

→ Any existing memory cells specific to the previous antigens would no longer be effective.

BIOLOGY, M7 EQ-Bank 23

The diagram shows the immune response after primary exposure to a pathogen.
 

  1. On the diagram, continue the graph to show the immune response upon secondary exposure to the same pathogen.   (2 marks)
  2. Using annotations on the diagram, explain the shape of the entire graph.   (4 marks)

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a. & b.

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a. & b.

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`

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→ 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 18 MC

Two people were exposed to pathogen `P` on the same day. The graph shows the blood antibody levels for that pathogen over the following 28 days for each person.
 

Which of the following best explains these results?

  1. Person 1 had not been previously exposed to pathogen `P` but had a recent organ transplant.
  2. Person 1 had been previously exposed to pathogen `P`.
  3. Person 2 had already been vaccinated against pathogen `P`.
  4. Person 2 had recent contact with a person infected with a similar pathogen.
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`B`

Show Worked Solution

By Elimination

→ Being vaccinated against a pathogen or being exposed to a similar pathogen would lead to higher antibody counts, not lower. (Eliminate C and D).

→ Person 1’s previous exposure to the pathogen means that memory B cells can quickly and rapidly differentiate into plasma B cells, leading to higher counts of antibodies in a shorter time. An organ transplant is not relevant in this scenario. (Eliminate A).

`=>B`


♦ Mean mark 50%.

BIOLOGY, M7 2019 HSC 16 MC

The diagram shows the concentration of an antibody to a particular pathogen.
 

Two students are exposed to the pathogen. Student `X` had previously been vaccinated against this pathogen. Student `Y` had never been exposed to it.

Which row of the table shows the most likely levels of antibody in the blood of each student a week after exposure to the pathogen on this occasion?

\begin{align*}
\begin{array}{l}
\rule[-1ex]{0pt}{0pt} \ \textit{Concentration of antibody in the blood}\ \text{(mg L\(^{-1}\))} \\
\end{array} \\
\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}{|c|c|}
\hline
\rule{0pt}{2.5ex} \ \ \quad \quad \textit{Student X}\quad\quad \ \ \rule[-1ex]{0pt}{0pt}& \ \ \quad \quad \textit{Student Y} \quad\quad \ \ \\
\hline
\rule{0pt}{2.5ex}250\rule[-1ex]{0pt}{0pt}&1500\\
\hline
\rule{0pt}{2.5ex}1500\rule[-1ex]{0pt}{0pt}& 1000\\
\hline
\rule{0pt}{2.5ex}1000\rule[-1ex]{0pt}{0pt}& 1500 \\
\hline
\rule{0pt}{2.5ex}1500\rule[-1ex]{0pt}{0pt}& 250 \\
\hline
\end{array}
\end{align*}

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\(D\)

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→ Student X has had previous exposure to the pathogen through vaccination and will respond with a high level of antibodies (similar to a secondary exposure).

→ Student Y has no previous exposure to the pathogen and will produce antibodies similar to that following a primary exposure (see graph).

\(\Rightarrow D\)

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%.