Explain how B-lymphocytes protect the body after a pathogen enters the bloodstream for the second time.

Edexcel GCSE Biology (1BI0) — 5.2 Pathogens and immunity · Explain · 4 marks · View as Markdown

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

When a person is exposed to the same pathogen more than once, their immune system responds much more rapidly and effectively than during the first infection.

Model answer (4 marks)

B‑lymphocytes recognise the antigen on the pathogen and produce specific antibodies.
Memory B‑lymphocytes formed after the first infection remain in the body.
On a second exposure these memory cells divide rapidly and produce large amounts of antibody.
The antibodies bind the pathogen and it is destroyed before symptoms develop, so the person does not become ill.

Examiner tips

  • Use the term "antibody" and "memory B‑lymphocyte". Show the sequence: recognition → antibody production → rapid memory response. Mention that the response is faster and stronger than the first.
  • Include that the pathogen is destroyed before symptoms appear.

Mark scheme (4 marks)

  1. B-lymphocytes produce antibodies specific to the antigen on the pathogen
  2. Memory cells / memory B-lymphocytes are retained after the first exposure
  3. On second exposure, memory cells divide rapidly and produce large quantities of antibodies quickly
  4. The pathogen is destroyed before symptoms develop / the person does not become ill

Key terms in this question

B-lymphocyte

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