# A patient is given a blood transfusion using blood from a donor whose antigens do not match their own. Explain why the patient's immune system attacks the transfused blood cells, and describe what happens during this immune response.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.3 Immune response · Explain · 5 marks

> When a patient receives a blood transfusion, the donor's blood cells must be carefully matched to the patient's blood type. If mismatched blood is given, the patient's immune system mounts a response against the donated cells.

## Mark scheme (5 marks)

1. The donor's blood cells carry different/foreign antigens on their surface
2. The antigens are recognised as foreign / non-self, triggering an immune response
3. B-lymphocytes produce antibodies specific to the foreign antigens
4. Antibodies bind to the foreign antigens on the donor blood cells
5. The donor blood cells are destroyed / clump together / are broken down, harming the patient

## Key terms

- [antigen](https://www.gradenine.co.uk/glossary/antigen)
- [immune response](https://www.gradenine.co.uk/glossary/immune-response)

## 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-given-a-blood-edcc3528) · Published by Druglandscape Ltd.