Transplantation

Question 1

Explain why organs are transplanted and where they come from

Answer 1

Organs are transplanted when they are failing or have failed or for reconstruction.

1. Life saving: liver, heart (LVAD), small bowel (TPN)
2. Life enhancing: pancreas or kidneys or cornea eye reconstruction

Types of transplantation

1. Autographs (stem cell - hearth)
2. Isografts (genetically identical)
3. Allografts (s9lid organs like kidneys, Bowles … lots) DECEASED AFTER STEM CELL OR AFTER CIRCULATORY
4. Xenografts (heart valves from pig and cow and skin)
5. Prosthetic

Question 2

Summarise the ethical and organisational transplant issues

Answer 2

Ethical: deceased after stem cell or circulatory and lots on that

Organisation: transplant selection (waiting list), transplant allocation, NHSBT establishes rules

What is fair/ timing/ urgency/ efficiency.

Question 3

Summarise the immunology of transplantation and its impact on organ allocation and rejection

Answer 3

7 elements to transplant: waiting time, HLA match and age combined, donor-recipient age difference, location of patient relative to donor, HLA-DR homozygosity, HLA-B homozygosity and blood group match.

The blood group: A and B proteins with carbohydrate chains on the RBC but also endothelial lining of blood vessels in transplanted organ. Also take into account naturally occurring anti-AB antibodies. ~ you could remove the antibodies in the recipient if incompatible via plasma exchange

HLA is the most important. They mediate adaptive immune response and stimulate t lymphocytes and inflammation. Highly polymorphic and has two different alleles because inherit from both mum and dad.

Question 4

Explain the risks and complications associated with transplantation

Answer 4

Rejection may occurs and can be diagnosed via histological examination of a graft biopsy (treated with immunosuppression).

T-cell mediated rejection: graft infiltration and activate CD4 and release of t killer cells which release the toxin granzyme B and punch holes in target cells (perforin) or apoptosis cell death via Fas ligand.

Antibody mediated rejection: antibody against HLA or AB antigen. Either pre transplantation or post (de novo). They will activate the complement pathway and may cause inflammation.

To monitor for rejection: kidney (rise in creatinine, fluid retention, hypertension). Liver transplant (rise in LFTs and coagulopathy).

Loads of drugs to immunosuppression Look on lecture