Treating Kidney Failure With Kidney Transplantation
VI. Finding a Good Match
The following section may seem difficult at first. However, you will be hearing these terms used many times during your evaluation and after your transplant. Take the time to get familiar with them, and don't be afraid to ask your transplant team if you have any questions.
An important part of the medical evaluation involves identification of your blood type and tissue type. This is especially important in living donor transplants since it helps to identify the best potential donor, but it is also important in finding a compatible cadaver donor.
- Blood Typing
In kidney transplant, it is important for the donor and recipient to have compatible blood types. Special proteins called antigens are used to determine your blood type. These antigens are found on the red blood cells and on the blood vessels inside your organs. The discovery of these antigens in 1940 is what made blood transfusions possible. There are four blood types: O, A, B and AB. People who are type O are called universal donors because their blood can be given to anyone. If you are blood type O, you can only accept blood from someone else who is also type O. Here is a chart to help you understand how different types of blood can be donated:"O" can receive from "O"
This is followed in living-related kidney transplants. However, because of the scarcity of cadaver kidneys, an "O" donor is only used for an "O" recipient in cadaver kidney transplants.
"A" can receive from "A" or "O"
"B" can receive from "B" or "O"
"AB" can receive from "O", "A", "B" or "AB"
Please note that there are some programs that may help donor/recipient pairs with blood types that are incompatible: paired exchange and plasmapheresis. Click here for more information. - Tissue Typing
Children inherit a set of 21 chromosomes from each parent. These chromosomes are the structures within your cells that contain the genetic material that determines who you are. The sixth chromosome carries the antigens that are important in kidney transplants. You may hear these called HLA, or human leukocyte antigens. The process of identifying these antigens is called tissue typing. The leukocytes, or white cells, in your blood carry these antigens and are used to identify them. More than 7,000 to 8,000 combinations of known antigens are possible.
Because you inherited a sixth chromosome from each parent, either parent could donate a kidney to you as long as he or she is healthy and has a blood type that is compatible with yours. A brother or sister could also be compatible if he or she inherited the same combinations as you did. - Percent Reactive Antibody (PRA)
This is another term you will hear often while being evaluated for a transplant. When you are exposed to antigens, either through a blood transfusion, pregnancy or previous transplant, you may develop an antibody to these antigens. It is important to test for the presence of these antibodies before your transplant. If you have a high level of antibodies, it may be more difficult to find a compatible kidney for you. - Serum Crossmatch
A serum crossmatch is done right before a kidney transplant. This test takes about four to five hours to complete. To do the test, cells from the donor are incubated with your serum. If your serum has antibodies against the donor's cells, the cells will be destroyed. This is called a positive crossmatch and it means that the transplant cannot take place. To do so would result in immediate rejection of the transplanted kidney.
The best potential donor is identified when tissue typing of all the immediate family members has been completed and their blood types have been identified. When this is done, the information is presented to the family, and the individual family member makes the decision to donate. He or she then calls the transplant office to make an appointment for an evaluation.
