Describe how the immune system responds when a pathogen enters the body for the first time, and explain why a person recovers more quickly if they are infected by the same pathogen a second time.

Eduqas GCSE Biology — 3.3 Treating, curing and preventing disease · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

White blood cells, particularly lymphocytes, recognise the pathogen’s antigens and produce specific antibodies that bind to those antigens.
During the first infection memory cells are created.
If the same pathogen enters again, the memory cells recognise it instantly and trigger a rapid, large‑scale antibody response, destroying the pathogen before serious illness develops.

Examiner tips

  • Use the term ‘antibodies’ and ‘memory cells’ – these are key words. Show the sequence: recognition → antibody production → memory cell formation → faster response on reinfection.
  • Mention that the second response is quicker and stronger, which is why recovery is faster.

Common mistakes

  • Confusing antibodies with T‑cells or failing to mention memory cells. Using vague phrases like ‘immune response’ without specifying antibodies or memory cells. Omitting the reason why the second response is faster (memory cells).

Mark scheme (4 marks)

  1. White blood cells / lymphocytes produce antibodies in response to the pathogen's antigens
  2. The antibodies are specific to / match / bind to the antigens on that pathogen
  3. Memory cells are produced during the first infection
  4. On second infection, memory cells allow antibodies to be produced more rapidly / in greater quantity, so the pathogen is destroyed before the person becomes seriously ill

Key terms in this question

pathogen

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