Via Thomas Peters, MD / AAKP
Scientists have known for many years that blood group matching is important in transfusion and it is equally important in kidney transplantation. The basic donation pathways in kidney transplantation are very similar to those used in blood transfusions.
There are four major blood types in humans. These types are simply noted as blood type A, B, AB and O. Another factor, the Rh factor, adds a plus or a minus following the above blood type letter, so that all of us have a blood type such as A+ or B- and so on. This plus or minus factor, however, relates only to a particular cell type in the blood and this factor is not part of the kidney. Thus, the positive or negative feature in blood typing has nothing to do with the matching of a kidney between a donor and a recipient. It remains, however, important in matching when a blood transfusion is considered. Because the positive and negative features of a blood type are not important in kidney matching, we will not further mention that aspect of matching.
In most circumstances, the person with blood type O is the universal blood donor. This means that a person with blood type O may donate to a person with any other blood type. A person with blood type A may donate to a person with blood type A or AB and a person with blood type B may donate to a person with B or AB. A person with blood type AB may only donate to an individual who has that same blood type.
Looking at this from the recipient’s point of view, a recipient with blood type O can receive a kidney only from a donor with blood type O. A recipient with blood type A may receive a kidney from a recipient with blood type O or A and a recipient with blood type B can receive a kidney from a donor with blood type O or B. Obviously, a recipient with blood type AB can receive a kidney from a person of any blood type.