Matching and Compatibility
You may have heard discussions about “matching” and kidney transplantation. There are actually three tests that are done to evaluate donors. They are blood type, crossmatch, and HLA testing. This blood test is the first step in the process of living donation and determines if you are compatible or a “match” to your recipient.
Blood Typing
There are 4 different blood types. The most common blood type in the population is type O. The next most common is blood type A, then B, and the rarest is blood type AB. The blood type of the donor must be compatible with the recipient. The rules for blood type in transplantation are the same as they are for blood transfusion. Some blood types can give to others and some may not. Blood type O is considered the universal donor. People with blood type O can give to any other blood type. Blood type AB is called the universal recipient because they can receive an organ or blood from people with any blood type. The chart below shows which blood type can donate to which.
| If your blood type is: | You can donate to these blood types: |
| TYPE O | TYPE O, A, B, AB |
| TYPE A | TYPE A, AB |
| TYPE B | TYPE B, AB |
| TYPE AB | TYPE AB |
HLA Typing
HLA typing is also called “tissue typing”. HLA stands for human leukocyte antigen. Antigens are proteins on the cells in the body. Out of over 100 different antigens that have been identified, there are six that have been shown to be the most important in organ transplantation. Of these six antigens, we inherit three from each parent.
Except in cases of identical twins and some siblings, it is rare to get a six-antigen match between two people, especially if they are unrelated. Kidneys are very successfully transplanted between two people with no matching antigens.
A person can make antibodies against another person’s HLA antigens. Antibodies can result from blood transfusions, pregnancy, infections or even a viral illness. Having one of these events does not mean a person will make antibodies but they could. If a recipient has strong antibodies against a donor’s HLA, the risk of rejection is high and a donor would be declined for that recipient.
