# Explain how the human immune system destroys a pathogen after it has entered the body. Include in your answer the roles of lymphocytes, antibodies and phagocytes.

> WJEC A-Level Biology (Wales) — 3.2 Respiration · Explain · 5 marks

## Mark scheme (5 marks)

1. White blood cells detect pathogens by identifying antigens on the pathogen's surface
2. Lymphocytes trigger the release of antibodies that are complementary/specific to the antigen
3. Antibodies bind to the antigens on the pathogen to neutralise it / antibodies cause agglutination (clumping together) of pathogens
4. Phagocytes ingest/engulf the pathogen
5. Phagocytes digest the pathogen using enzymes, making it harmless

## Key terms

- [lymphocyte](https://www.gradenine.co.uk/glossary/lymphocyte)
- [phagocyte](https://www.gradenine.co.uk/glossary/phagocyte)

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-human-immune-system-e55eb034) · Published by Druglandscape Ltd.