# HIV is a communicable disease caused by a virus. Explain how the human body responds to HIV once it has entered the bloodstream, including the roles of lymphocytes, phagocytes and memory cells.

> Eduqas A-Level Biology — 3.5 Human impact on the environment · Explain · 5 marks

## Mark scheme (5 marks)

1. White blood cells detect the HIV virus using receptors on their cell surface to identify antigens on the pathogen
2. Lymphocytes release antibodies that are specific / complementary to the antigens on HIV, which bind to the antigens to neutralise the virus
3. Lymphocytes activate phagocytes / antibodies clump HIV particles together (agglutination) making them easier for phagocytes to destroy
4. Phagocytes engulf / ingest HIV particles and digest them using enzymes (phagocytosis)
5. Memory cells remain after the infection so that if HIV is encountered again, the immune response is faster / antibodies are produced more quickly

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](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/hiv-is-a-communicable-disease-caused-147a92a8) · Published by Druglandscape Ltd.