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Varicella (chickenpox) is a highly contagious disease caused by the varicella zoster virus - VCE - SSCE Biology - Question 4 - 2021 - Paper 1
Question 4
Varicella (chickenpox) is a highly contagious disease caused by the varicella zoster virus. A live, attenuated varicella zoster virus vaccine is recommended for chil... show full transcript
Worked Solution & Example Answer:Varicella (chickenpox) is a highly contagious disease caused by the varicella zoster virus - VCE - SSCE Biology - Question 4 - 2021 - Paper 1
Step 1
Summarise the immune response that occurs within the child to result in long-term protection from chickenpox.
Answer
When the varicella zoster virus vaccine is administered, it introduces a harmless form of the virus into the child's body. This triggers an immune response through several key mechanisms:
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Antigen Presenting Cells (APCs): The vaccine's antigens are taken up by APCs, such as macrophages and dendritic cells. These cells process the antigens and present them on their surface to T cells.
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Activation of Helper T Cells: The presented antigens activate Helper T cells, specifically CD4+ T cells, which play a crucial role in orchestrating the immune response.
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B Cell Activation: Activated Helper T cells stimulate naïve B cells to differentiate into plasma cells that produce antibodies specific to the varicella virus.
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Memory Cell Formation: Some B cells develop into memory B cells and T memory cells, providing long-term immunity by allowing for a quicker, more robust response upon future exposure to the virus.
Step 2
What is the benefit of having two doses instead of one dose? Justify your response.
Answer
The benefit of having two doses of the varicella zoster virus vaccine lies primarily in the enhancement of the immune response:
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Increased Antibody Production: The first dose leads to the initial activation of B cells, resulting in a small number of memory cells. The second dose significantly increases the number of memory cells and generates a larger quantity of antibodies, ensuring stronger immunity against future infections.
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More Rapid Response: With the increased number of memory cells, the body is more prepared to respond quickly and effectively if exposed to the varicella virus again, leading to a reduced risk of severe illness and complications.
This two-dose strategy not only strengthens the immune system's response but also prolongs protection against the disease.
Step 3
Outline similarities and/or differences in active and passive ways of acquiring immunity.
Answer
Active and passive immunity are two distinct methods of acquiring immunity, each with its own characteristics:
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Active Immunity:
- Definition: Results from the body's own immune response to an antigen.
- Duration: Long-lasting, often for years or even a lifetime.
- Examples: Vaccination (like the varicella vaccine) and natural infection (recovering from chickenpox).
- Mechanism: The body produces its own antibodies and memory cells when exposed to the antigen.
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Passive Immunity:
- Definition: Involves the introduction of antibodies from an external source.
- Duration: Temporary, usually lasting a few weeks to months.
- Examples: Maternal antibodies transferred to a baby through breast milk or injections of antibodies (e.g., immunoglobulin therapy).
- Mechanism: The body does not produce its own immune response; instead, it receives pre-formed antibodies.
Similarities: Both active and passive immunity contribute to protection against infections and can help in preventing diseases. Both mechanisms involve the immune system's engagement with pathogens to ensure the body is prepared for exposure.