Describe how white blood cells defend the body after a pathogen has entered the bloodstream.

Cambridge International IGCSE Biology (0610) — 10.1 Diseases and immunity · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

1. Phagocytes, such as neutrophils and macrophages, recognise and engulf pathogens by phagocytosis, destroying them inside phagosomes.
2. Lymphocytes, including B‑cells and T‑cells, recognise specific antigens on the pathogen’s surface.
3. B‑cell lymphocytes produce antibodies that are complementary to the antigen.
4. The antibodies bind to the antigen, causing clumping of pathogens or marking them for destruction by phagocytes.

Examiner tips

Use the exact terminology (phagocytes, lymphocytes, antibodies, antigen).
Show the sequence: phagocytosis → antigen detection → antibody production → antibody‑mediated destruction.
Include both clumping and marking for phagocytosis as outcomes of antibody action.
Keep each point concise and separate with numbers or bullet points.

Common mistakes

Confusing neutrophils with lymphocytes; they are different cell types.
Omitting the role of B‑cells in antibody production.
Failing to mention that antibodies can cause clumping (agglutination).

Mark scheme (4 marks)

Phagocytes engulf and destroy pathogens by phagocytosis
Lymphocytes detect specific antigens on the surface of the pathogen
Lymphocytes produce specific antibodies complementary to the antigen
Antibodies bind to antigens causing pathogens to clump together / be marked for destruction by phagocytes

Key terms in this question

pathogen