Explain how white blood cells protect the body after a pathogen enters the bloodstream for the first time.

Eduqas GCSE Biology — 2.6.2 The immune system · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

1. White blood cells recognise antigens on the pathogen’s surface.
2. They produce antibodies that are complementary to those antigens.
3. The antibodies bind to the antigens, neutralising or clumping the pathogens.
4. White blood cells can also engulf, ingest and digest the pathogens (phagocytosis).

Examiner tips

Use the exact terminology – ‘recognise’, ‘antigens’, ‘antibodies’, ‘phagocytosis’.
Show the sequence: detection → antibody production → binding → destruction/engulfment.
Keep each point brief – one sentence per mark.
Use UK spelling (recognise, defence).

Common mistakes

Confusing antibodies with white blood cells – they are produced by B‑cells, not all WBCs.
Using ‘kill’ instead of ‘neutralise’ or ‘clump’ – examiners look for specific mechanisms.
Omitting the phagocytosis step or describing it as ‘eating’ without mentioning digestion.

Mark scheme (4 marks)

White blood cells detect/recognise antigens on the surface of the pathogen
White blood cells produce antibodies specific/complementary to the antigens
Antibodies bind to/attach to the antigens, destroying/neutralising/clumping the pathogens
White blood cells can also engulf/ingest and digest pathogens (phagocytosis)

Key terms in this question

pathogen