The Importance of Blood Type Compatibility in Blood Transfusions

Why is only the donor’s antigen seen during a blood transfusion?

During a blood transfusion, it is essential to match the blood types of the donor and the recipient to ensure compatibility. This is because red blood cells (RBCs) in our body possess specific antigens on their surface, which determine our blood type.

The two most important blood typing systems are the ABO system and the Rh system. In the ABO system, there are four blood types: A, B, AB, and O. Each blood type has a unique combination of antigens on the surface of RBCs. Blood type A has A antigens, blood type B has B antigens, blood type AB has both A and B antigens, and blood type O has no antigens.

When a blood transfusion occurs, the immune system of the recipient recognizes the foreign (non-self) antigens on the RBCs. If the recipient’s immune system encounters an antigen that it does not possess, it produces antibodies against that specific antigen. These antibodies act as a defense mechanism, targeting and destroying the foreign RBCs, leading to a potentially life-threatening immune reaction.

To avoid these complications, blood transfusions are carefully matched to ensure compatibility. For example, if a person with blood type A receives blood from a person with blood type B, the recipient’s immune system will recognize the presence of the foreign B antigens on the transfused RBCs. In response, the immune system will produce antibodies against the B antigens, leading to an immune reaction that can cause the destruction of the donor’s RBCs.

However, if a person with blood type A receives blood from a person with the same blood type (A or O in this case), the RBCs of the donor will not contain foreign antigens to which the recipient’s immune system will react. Hence, only the donor’s antigen will be seen during a blood transfusion because the recipient’s immune system will not produce antibodies against the donor’s RBCs.

In summary, matching the blood types of the donor and recipient is crucial to avoid immune reactions. If a transfusion involves blood with antigens foreign to the recipient’s immune system, the immune response can lead to destruction of the donor’s RBCs and potential health risks. Therefore, ensuring a compatible blood type minimizes the risk of such harmful reactions during blood transfusions.

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