Explain why a person who has received a transplanted organ may need to take immunosuppressant drugs for the rest of their life.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Organ transplants save thousands of lives each year. However, recipients must take medication to prevent their immune system from attacking the transplanted organ.
Model answer (5 marks)
The transplanted organ carries antigens that differ from the recipient’s own cells, so the immune system recognises them as foreign. This triggers an immune response, with lymphocytes and antibodies attacking the graft – a process known as rejection. Immunosuppressant drugs inhibit key steps in the immune response, reducing the production of antibodies and the activity of T‑cells that would otherwise destroy the organ. Because the foreign antigens remain on the graft indefinitely, the drugs must be taken continuously to keep the immune system suppressed and prevent ongoing rejection.
Examiner tips
- Use the term ‘antigens’ and ‘foreign/non‑self’ to show understanding of recognition.
- Explain the sequence: antigen → immune response → rejection, then drug action.
- Mention that continuous treatment is required because antigens are always present.
Common mistakes
- Confusing ‘antigens’ with ‘antibodies’ or vice versa.
- Failing to state that the drug action is to suppress the immune response, not to kill the organ.
- Assuming the drug is only needed temporarily rather than lifelong.
Mark scheme (5 marks)
- The transplanted organ has different antigens (on its cell surface) to the recipient's own cells
- The recipient's immune system recognises the organ's antigens as foreign / non-self
- The immune system produces antibodies against / attacks the transplanted organ (rejection)
- Immunosuppressant drugs reduce / suppress the immune response
- The drugs must be taken continuously because the organ's foreign antigens are always present / the immune system would otherwise keep responding
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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