# Explain how the human body defends itself against pathogens using both non-specific defences and the immune system.

> WJEC A-Level Biology (Wales) — 3.1 Photosynthesis · Explain · 5 marks

> The human body has several layers of defence against pathogens. These include non-specific defences that are always present and a specific immune response that is triggered when a pathogen enters the body.

## Mark scheme (5 marks)

1. Named non-specific defence acting as a barrier (e.g. skin, mucus, stomach acid, hairs in the nose, blood clotting)
2. White blood cells detect pathogens by identifying antigens on the pathogen's surface
3. Lymphocytes release antibodies that are specific/complementary to the antigen and bind to it to neutralise the pathogen / antibodies cause agglutination
4. Phagocytes engulf and digest pathogens (phagocytosis) using enzymes
5. Memory cells remain after infection so that if the same pathogen is encountered again, antibodies are produced more quickly

## Key terms

- [non-specific defence](https://www.gradenine.co.uk/glossary/non-specific-defence)

## 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-body-defends-d8d1db03) · Published by Druglandscape Ltd.