Kidney Transplants: Matching, Rejection and Immunosuppression
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
A kidney transplant replaces a failed kidney with a healthy donor kidney. The donor must be tissue-matched to minimise rejection by the recipient's immune system. The patient takes immunosuppressant drugs for life. A successful transplant eliminates the need for dialysis.
Kidney transplants are compared with dialysis in exam questions. You need to explain why rejection occurs (the immune system recognises the donor kidney as foreign tissue) and how it is managed (tissue matching and immunosuppressant drugs).
Tissue matching and rejection
Every person's cells have unique antigens on their surface. The immune system recognises cells with different antigens as foreign and attacks them. If a transplanted kidney has very different antigens from the recipient, the immune system will mount a response: lymphocytes produce antibodies that attack the donor kidney. This is rejection.
To reduce rejection risk, the donor kidney is tissue-matched: a donor is chosen whose cell-surface antigens are as similar as possible to the recipient's. Close relatives are often the best match. Even with good matching, some difference remains, so additional measures are needed.
Immunosuppressant drugs
After transplantation, the recipient must take immunosuppressant drugs for the rest of their life. These drugs reduce the activity of the immune system, preventing it from rejecting the donor kidney. However, a suppressed immune system is less effective at fighting infections, so transplant patients are more vulnerable to infectious diseases.
This trade-off: protection of the transplanted organ versus increased infection risk: is a significant consideration. Patients must be carefully monitored and may need to avoid contact with people who have transmissible diseases.
Advantages and disadvantages compared to dialysis
Factor
Transplant
Dialysis
Freedom
Normal lifestyle possible
Regular hospital visits; restricted diet
Duration
Can last many years (often 15–20+)
Indefinite, as long as needed
Risks
Surgery risk; rejection; infection from immunosuppression
Infection at access point; cardiovascular strain
Availability
Limited by donor organ shortage
Always available
Cost
High initial cost; lower long-term
Lower initial cost; high ongoing cost
Try a focused question (3 marks)
Explain why a person who receives a kidney transplant must take immunosuppressant drugs.
Show the answer and marking guidance
The donor kidney has different antigens on its cell surfaces compared to the recipient.
The recipient's immune system would recognise these as foreign and produce antibodies to attack the kidney (rejection).
Immunosuppressant drugs reduce the immune response, preventing rejection of the transplanted kidney.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Saying the body rejects the kidney because it is not the right blood type: rejection is about tissue antigens, not just blood group.
Forgetting that immunosuppressant drugs increase vulnerability to infections.
Claiming transplants always work permanently: they can fail or be rejected over time.
Not mentioning that a tissue-matched donor is needed to reduce rejection risk.