What is Transplantation Immunology?

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The term "transplantation" means removing something from one location and introducing it in another location, hence in immunology the term transplantation is used to refer the procedure involved in the replacement of a nonfunctional or damaged organ or tissue with a good, and functional organ or tissue to safe guard the life of an individual.

The implanted tissue or organ is known as "graft". Organs that can be transplanted are heart, kidneys, liver, lungs, pancreas, penis, eyes and intestine.

Tissues include bones, tendons, cornea, heart valves, veins and skin. The advancement in surgical techniques introduced the idea of transplantation of required organs or tissues. It is now possible to transfer a variety of tissues and organs from a healthy donor to an ailing recipient or from one site to another in the same individual (eg. skin grafting in burn cases) through sugery.

Even though development in surgical techniques allowed clinicians to perform transplantation of organs or tissues, certain barriers such as availability of donors, expenditure for the clinical procedure and implant rejection reactions etc. made it a difficult and cumbersome procedure.

Since the immune system has been evolved to protect its own self from the attack of foreign bodies, it holds the power of identifying its own cells from foreign cells.

Cells express a set of membrane bound antigens called auto antigens. The auto antigens act as identification marks for the immune system to identify its own cells from foreign cells.

Immune system identifies the graft through the antigens present on their cells and reacts in a similar way as it reacts to a pathogen.

Hence the unique power of immune system is responsible for graft rejection. But immunological rejection is exempted for genetically identical or allograft (Own tissue taken from some other region), because the antigens present on the graft tissue are identical with its own antigens and immune system fails to identify them as foreign cells to mount any action.

First systematic study of transplantation was reported in 1908 by Alexis Carrel. In 1935 a Russian surgeon attempted the first human kidney transplant, but mismatch of blood group between donor and recipient induced a rejection reaction.

The first successful human kidney transplant between identical twins was succeeded in 1954. Many failures in transplantation procedure insist the importance of knowledge in immunobilogy.

Discovery of human blood groups was one of key event that helped to understand the cause for transplant rejection. Now it is understood, that matching of donor and recipients blood groups is essential for the survival of tissue grafts, because the vascular endothelium express blood group antigens.

Matching of blood group antigens other than A, B, AB, O is not critical for transplantation, because they are expressed only on red Blood cells.

Study of Mouse skin graft rejection further improved the knowledge of transplantation immunology, and it helped a lot in understanding major histo compatibility antigens.

As recognition of foreign cells by recipient T cells is associated with MHC antigens of foreign cells, knowledge about MHC is essential to understand transplantation reactions.


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