Transplantation is the surgical process where tissues or organs are transplanted – or “grafted” – from one individual to another or from one site to another on the same person. Transplantation allows damaged or dysfunctional organs/tissue to be replaced and allows the person to function normally again.
The first transplant operation to be carried out successfully was the grafting of the cornea of the eye!
One of the main hurdles that affects the transplant surgeon is the rejection of the transplanted tissue by the body which detects the organ as a foreign body. This means that any transplanted organ ellicits an immune reaction from the body, an immune reaction that tries to destroy the newly transplanted organ! Exceptions to this rule are cartilage and corneal tissue as these areas have poor blood supplies and therefore the immune cells do not often travel via the blood system to these areas.
To prevent rejection of the transplant, it is necessary to interfere with the body’s immune system – medication has to be taken that suppresses the immune system making it weaker and therefore any reaction is unlikely to damage or destroy the transplant. This means that tranplantees are prone to infection as their immune system is weaker due to the drugs they are taking.
The exception to this is when tissue is transfered from one site of that person to another site of the same person. As the transplant is considered “self” it is not rejected.
Preparing for a Transplant
As soon as a foreign transplant is placed in the body, the body’s immune system sends cells to “investigate” the “invader”. These cells quickly determine whether the transplant is foreign or “self” and ellicits the appropriate response – rejection! White blood cells quickly surround the transplant and release chemical agents which are intended to suppress, subdue and destroy the foreign transplant.
In order to lessen the likelihood of rejection, two factors have to be considered:
- Tissue Typing
- Tissue typing describes the procedure by which doctors compare the cells on the transplant to the cells in the host (person receiving the transplant) – the closer the match the lesser the likelihood of rejection. There are four main tissue types A, B, C and D – generally, tissue that are compatible with all four have the least chance of rejection, but for practical purposes, tissue that matches A,B and C as closely as possible is considered a good match.
- Usually, transplant organs or tissues from the parents or the siblings of the patient is the best option as there is a greater chance of compatibility. The doctors must also match up the four blood groups – A, B, AB and O!
- Immunosupression describes the medications used to suppress the immune system to prevent rejection. Drugs such as corticosteroids, azathioprine, cyclophosphamide and others are used to suppress the immune system and prevent excessive production of white blood cells. Side effects include – infection, inflammation of the pancreas, duodenal ulceration, diabetes , kidney or liver damage, osteoporosis and tumours of the lymphoid (immune cell collections) system.
There are always more people in need of transplants then there are healthy people available to donate tissue or organs. As such medical science relies on organs donated by those who have recently died, usually due to accident.
The table below shows the times within which donor organs must be used from the time they are removed:
|Kidney||48 hrs||if stored cold|