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# Blood Transfusions

## Blood Transfusions

Blood transfusions often save the lives of people whom have lost large amounts of blood due to trauma caused by accidents and surgery. Before a person receives blood from a blood donor, the blood has to be typed to see if the donor is a match for the recipient. Blood is classified based on the presence of antigens in the red blood cells. An antigen is a molecule recognised by the immune system. There are four different types of blood groups. Recipients can only be given blood which is compatible to their own blood.

• Blood Group A has antigen A only
• Blood Group B has antigen B only
• Blood group AB has both antigen A and B
• Blood Group O has neither antigens A or B

The table below shows the different ABO Blood Groups and compatibility for blood transfusions.

 Blood group Blood donor (person giving blood) Blood recipient (person requiring blood) A A and AB A and O B B and AB B and O AB AB only All groups O All groups O only

Red blood cell compatibility chart. In addition to donating to the same blood group, type O blood donors can give to A, B and AB; blood donors of types A and B can give to AB.

Furthermore, the Rhesus factor of both the recipient and donor need to be determined. The Rhesus factor is another type of antigen found on the surface of red blood cells. Approximately $$\text{85}\%$$ of the population has this protein and are know to be Rhesus positive. The remaining $$\text{15}\%$$ of the population are Rhesus negative because this protein is not present in their red blood cells.

So, blood group A negative means the recipient has antigen A, but does not have the Rhesus factor, a recipient who is O positive means the recipient has neither antigen A or B but does have the Rhesus factor. It is important that a person receiving a blood transfusion receives blood from a donor that is compatible in both blood group and Rhesus factor.

## Video: What are Blood Types?

What are blood types? Watch this video below by SciShow to find out.