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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
The immune response to the varicella zoster virus vaccine follows several steps:
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Antigen Presentation: After the vaccine is administered, the live attenuated virus is detected by immune cells, such as macrophages. These cells process the virus and present its antigens on their surface.
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Activation of T Cells: The antigen-presenting cells migrate to the lymph nodes, where they interact with helper T cells. This activation leads to a robust immune response.
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B Cell Activation: Helper T cells stimulate naive B cells to differentiate into plasma cells, which produce specific antibodies against the varicella zoster virus.
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Memory Cell Formation: The immune response also generates long-lived memory B cells and T memory cells. These cells are crucial for rapid response upon re-exposure to the virus, providing long-term immunity against chickenpox.
Step 2
What is the benefit of having two doses instead of one dose? Justify your response.
Answer
The primary benefit of receiving two doses of the varicella zoster virus vaccine is:
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Enhanced Immunogenicity: The first dose leads to the activation of B cells and the formation of a small number of memory cells. The second dose significantly increases the number of memory cells, thereby improving the immune system's ability to respond to subsequent infections more quickly and effectively.
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Stronger Antibody Production: The second dose promotes a more robust and higher titer of antibodies, enhancing protection against chickenpox and reducing the likelihood of breakthrough infections. This strategy helps to ensure better long-term immunity.
Step 3
Outline similarities and/or differences in active and passive ways of acquiring immunity.
Answer
Immunity can be acquired actively or passively:
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Active Immunity:
- Definition: Active immunity occurs when the immune system is stimulated to produce antibodies in response to an antigen, either through infection or vaccination.
- Duration: It usually provides long-lasting protection, as memory cells are formed.
- Example: Vaccination against varicella zoster virus or recovering from a chickenpox infection.
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Passive Immunity:
- Definition: Passive immunity involves the transfer of pre-formed antibodies to an individual, providing immediate but temporary protection.
- Duration: It is short-lived, typically lasting a few weeks to months, as the recipient does not produce their own antibodies.
- Example: Receiving immunoglobulin injections or maternal antibodies passed through breast milk.
In summary, the main difference lies in the method of antibody acquisition and the duration of protection.