# Describe how the human body responds to a pathogen that has entered the bloodstream, including the roles of lymphocytes, antibodies and phagocytes.

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

## Mark scheme (5 marks)

1. White blood cells detect the pathogen by identifying antigens on its surface
2. Lymphocytes release antibodies that are specific / complementary to the antigen
3. Antibodies bind to antigens on the pathogen to neutralise it / cause agglutination (clumping together of foreign cells)
4. Phagocytes engulf / ingest and digest the pathogen using enzymes (phagocytosis)
5. Memory cells remain after infection so that the same pathogen can be destroyed more quickly if it enters the body again

## Key terms

- [pathogen](https://www.gradenine.co.uk/glossary/pathogen)
- [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 "Describe" 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/describe-how-the-human-body-responds-33047fce) · Published by Druglandscape Ltd.