# A patient is diagnosed with HIV. Over several years, the number of white blood cells in the patient's body decreases significantly. Explain why this patient becomes increasingly unable to fight off other infections, and describe what this condition is called when the immune system can no longer function effectively.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 6 Immunity, Infection and Forensics · Explain · 5 marks

> HIV is a virus that targets and destroys specific white blood cells involved in the immune response. A patient infected with HIV may initially show few symptoms, but over time the immune system becomes severely compromised.

## Mark scheme (5 marks)

1. White blood cells (lymphocytes) produce antibodies to fight infection
2. HIV destroys/reduces the number of white blood cells (lymphocytes)
3. Fewer white blood cells means fewer antibodies can be produced
4. The body cannot mount an effective immune response / cannot recognise and destroy pathogens
5. This condition is called AIDS (Acquired Immune Deficiency Syndrome) / the immune system is described as deficient or compromised

## Key terms

- [white blood cells](https://www.gradenine.co.uk/glossary/white-blood-cells)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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/a-patient-is-diagnosed-with-hiv-021f326e) · Published by Druglandscape Ltd.