Blood Type

There are 4 types of blood: A, B, AB and O. Your blood type is determined by the genes you inherit from your parents. Blood is made up of red blood cells, white blood cells and platelets in a liquid called plasma. Your blood type is identified by antibodies and antigens it contains. Antibodies are proteins found in plasma. They form your body’s natural defenses against germs. When germs are recognized, your immune system starts to activate and kills the germs. Antigens are protein molecules found on the surface of red blood cells.

The following are the four main blood groups:

1. Blood group A. his group has A antigens on the red blood cells with anti-B antibodies in the plasma;

2. Blood group B has B antigens with anti-A antibodies in the plasma;

3. Blood group O has no antigens, but both anti-A and anti-B antibodies in the plasma;

4. Blood group AB has both A and B antigens but no antibodies.

Blood group O is the most common blood group. Receiving the right blood group is very important because the wrong blood group can be life-threatening to certain recipients. For example, if a person with group B blood is given an infusion with group A blood, their group A cells anti-A antibodies will attack the group A cells. As a group O red blood cells do not have any A or B antigens so it can be given to any other group.

Red blood cells can have another antigen, a protein known as RhD antigen. If this is present, your blood is RhD positive. If is absent, your blood group is RhD negative. In other words you can be one of 8 possible groups:

1. A RhD positive (A+)

2. A Rhd Negative (A-)

3. B Rhd positive (B+)

4. B Rhd negative (B-)

5. O Rhd positive (O+)

6. O Rhd negative (O-)

7. AB Rhd positive (AB+)

8. AB Rhd negative (AB-)

Most people are RhD positive. O RhD negative blood (O-) can be given safely to anyone. It is most often given in medical emergencies when blood type is not immediately known. It is safe for most recipients because it does not have any A, B or RhD antigens on the surface of the cells and is compatible with every other ABO and RhD blood group.