Explain how white blood cells defend the body against pathogens that have entered the bloodstream.

Eduqas GCSE Biology — 3.1 Health and disease · Explain · 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 protect the body by two main mechanisms. First, phagocytic cells such as macrophages and neutrophils engulf and destroy pathogens that enter the bloodstream. Second, lymphocytes produce antibodies that recognise specific antigens on the pathogen. The antibodies bind to the pathogens, marking them for destruction, clumping them together or neutralising them, and some white blood cells also produce antitoxins that neutralise toxins released by the pathogens.

Examiner tips

  • Use the phrase ‘phagocytosis’ and ‘antibodies’ – these are key terms. Show the two main mechanisms: engulfment and antibody action. Mention that antibodies can clump or neutralise pathogens. Include that some cells produce antitoxins to neutralise toxins.

Common mistakes

  • Confusing red blood cells with white blood cells. Failing to mention both phagocytosis and antibody production. Using vague terms like ‘fight’ instead of ‘engulf’ or ‘bind’.

Mark scheme (4 marks)

  1. White blood cells can engulf and destroy pathogens by phagocytosis
  2. White blood cells produce antibodies that are specific to the antigens on the pathogen
  3. Antibodies bind to the pathogens, causing them to be destroyed or clumped together / neutralised
  4. White blood cells also produce antitoxins that neutralise toxins released by pathogens

Key terms in this question

white blood cells

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