Explain why a person who has recovered from chickenpox is unlikely to get chickenpox again.

AQA A-Level Biology (7402) — 3.2.4 Cell Recognition and the Immune System · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Chickenpox is a disease caused by a virus. After a person recovers from chickenpox, their immune system retains a 'memory' of the virus.

Model answer (5 marks)

The chickenpox virus displays specific antigens on its surface. When the first infection occurs, lymphocytes recognise these antigens and produce antibodies that are complementary to them. Some of these lymphocytes become memory cells and remain in the body after recovery. On a second exposure, the memory cells recognise the same antigens immediately and trigger a rapid, large‑scale antibody response, which destroys the virus before symptoms develop.

Examiner tips

  • Use the term ‘antigens’ and ‘antibodies’ explicitly; link lymphocytes to memory cells. Show the sequence: antigen → antibody → memory cell → rapid response. Keep the answer concise and to the point.

Common mistakes

  • Confusing antibodies with T‑cells; forgetting to mention memory cells; writing a long narrative instead of a concise explanation.

Mark scheme (5 marks)

  1. The virus has specific antigens on its surface
  2. White blood cells (lymphocytes) produce antibodies that are complementary to / specific to those antigens
  3. Memory cells are produced / remain in the body after the first infection
  4. On second exposure to the chickenpox virus, memory cells recognise the antigens
  5. Antibodies are produced more quickly / in greater quantities, destroying the virus before symptoms develop

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