Thursday, 15 September 2011
Give Us A Hand (post 1 of 2)
57 years ago, Joseph Murray and his team at the Peter Brent Brigham Hospital in Boston performed a landmark surgery. For the first time it was possible to take a liver from one individual and successfully insert it to another, thus beginning the age of transplantation. Transplantation is a procedure that is now commonplace in many countries, for example, last year in the UK nearly 4000 organ transplants were carried out. However, transplantation is not without its complications and risks. Even when successful, a patient is still not out of the woods and for the rest of their life they are required to take a cocktail of immunosuppressive drugs and yet may still need a new transplantation within 10 years. As an example, the 10-year survival rate for a first time transplant of a deceased donor kidney is only 48%. What I’d like to look at with you here is why it is necessary for a patient to continue to take so many drugs and what the future may hold for the field of transplantation.
Any patient who receives a transplanted organ must take a vast array of immunosuppressive drugs for the rest of their life. These drugs are vital for survival of both the patient and the organ, due to the immune system being finely tuned to attack anything it sees as foreign, such as someone else’s organ. Our immune system must be able to recognise and attack invading microbes that look to cause damage (known as pathogens) while at the same time not attack our own cells (self-cells). Therefore the immune system must be able to distinguish between self and non-self (pathogens) in order to be of any use. Detection of anything by the immune system is achieved through the binding of immune cells to molecules on other cells. The molecules the immune system binds to on pathogens are simply known as antigens, while the (main) molecule used to detect self is known as the HLA (human leukocyte antigen). The HLA is a wonderfully complex molecule and I will probably write a whole blog on it at some later date but for now the extent of the detail I will go to is to say that unless two people are genetically identical (eg. identical twins) they will not have the same HLA; your HLA is as unique as you are. You may now be starting to see where I’m going with this. Since your HLA is unique to you and stops your immune system attacking your cells, if you receive an organ from someone not genetically identical its cells will have a totally different HLA – to the immune system this appears no different to an antigen on a pathogen, giving the immune system the license to attack. If it weren’t for immunosuppressive drugs all transplanted material would simply be destroyed by the recipient’s immune system, a phenomenon known as rejection. This is the main reason for the failure of any transplant operation and can occur anywhere from minutes after the operation to years later, hence the need for immunosuppression for the rest of life.
Transplantation of organs is no doubt a fantastic achievement but it isn’t without its complications and dangers. These problems are not the only issues facing transplantation, as there is also a distinct lack of donor tissue, in the US for example, it is estimated there is a deficit of 4000 livers each year. Without going into the debate of whether organ donation should be an opt-out system (something I believe) there is clearly a need for improvement in availability and safety. But what is the work being done to tackle these issues?