Transplantation : part 2

Question 1

What must be confirmed with DBD(donor after brain stem death) donors?(Neurological criteria of death)

Answer 1

Irremediable structural brain damage of known cause Apnoeic coma that is NOT due to depressant drugs, hypothermia, neuromuscular blockers etc. Must be able to demonstrate a lack of brain stem function (e.g. pupillary reflex absent)

Question 2

How are the organs maintained once they’ve been removed?

Answer 2

They are rapidly cooled and perfused NOTE: absolute maximum cold ischaemia time for the kidneys is 60 hours

Question 3

What are the 5 tiers of patients on the organ transplant waiting list based on?

Answer 3

Paediatric or adult, Highly sensitised or not

Question 4

Describe some other strategies for increasing transplantation activity.

Answer 4

Use marginal donors e.g. elderly and sick .Transplantation across compatibility barriers .Exchange programmes – organ swaps for better tissue matching. Future – xenotransplantation + stem cell research.

Question 5

What are the main antigens that must be considered when determining the compatibility of an organ for transplant?

Answer 5

ABO HLA

Question 6

What are the most important HLA subtypes in organ compatibility and why are they known as such?

Answer 6

A B DR becuase they are the most polymorphic and they therefore have the highest chance of causing graft injury.

Question 7

How may organ rejection present?

Answer 7

Deteriorating graft function e.g. rise in creatinine with kidney transplant, Pain and tenderness over graft ,Fever

Question 8

Describe the treatment of episodes of acute rejection.

Answer 8

T cell mediated: steroids and anti-T cell agents Antibody mediated: IVIg, plasma exchange, anti-CD20, anti-complement

Question 9

What happens in T-cell mediated rejection of the graft

Answer 9

A delayed type hypersenssivity response, where APCs cosume the antigen and display par of the antigen on it’s MHC. APCs migrate to lymph nodes and present the antigen to the cd4+ T cells . These T cells then migrate and infiltrate the organ

The T cells recruit a number of other cells, including:

cytotoxic T-cells and macropahges

Question 10

How many mismatches can you have with a potential donor.

Answer 10

between 0 and 6

Question 11

Give examples of life-saving and life-enhancing transplantation

Answer 11

• Life-saving
• liver
• heart (LVAD – left ventricular assist device)
• small bowel (TPN - total parenteral nutrition)
• Life-enhancing
• Kidney – dialysis
• Pancreas – in selected cases, tx better than insulin injections

Question 12

Describe Post transplantation infections you can get as a result of immunosupression

Answer 12

•Increased risk for conventional infections

–Bacterial, viral, fungal

•Opportunistic infections – normally relatively harmless infectious agents give severe infections because of immune compromise

–Cytomegalovirus

–BK virus

–Pneumocytis carinii (jirovecii)

Question 13

Expli the basis behind the ABO classification and why it is imporant

Answer 13

•A and B proteins with carbohydrate chains on red blood cells but also endothelial lining of blood vessels in transplanted organ. A and B proteins/antigens have different carbohydate chainfs on them. Some red blod cells just have a A protein( A group), some have a B(B group) , some ahve both(AB group). Some have none (O group). We express antibodies for the the entogens that we do not have , therefore if an organ is transplated from a donor of incompatible ABO group the antibodies will bind to antigens on the donor endothelium leading to anti-body mediated rejection.