What’s in a Blood Type?

Have you ever wondered about your blood? What makes type A different from type B? Maybe you are a blood donor and are curious why your blood type is different than your parents or siblings?

What determines the blood type is proteins found on blood cells called antigens. The antigens that are most commonly used to type blood are called type A, type B, and the Rhesus factor. If you have the A antigens, then your are blood type A. If you have the B antigens, then you are blood type B. If you have both A and B antigens, then you are blood type AB. If you lack these antigens completely (i.e., you have neither A or B antigens) then you are blood type O. The Rhesus factor is classified as to whether you have that protein (positive) or you lack the Rhesus protein (negative). Putting this all together, someone with a A antigens and the Rhesus factor would therefore have blood type A+. Someone with ALL of these antigens, A, B, and Rh, would be blood type AB+ and someone who lacks all of these antigens would be blood type O-.

Now, these antigens don’t really make a difference to your health, anymore than the colour of your eyes or hair. They will, however, make a difference if you receive a blood product, say for a surgery or something. You can only receive blood that is compatible with your blood type. To be compatible, the blood you receive must not contain any antigens that you don’t already posses. This is because the presence of foreign proteins will cause an immune reaction, which produces immune proteins called antibodies. The blood type O- has no antigens and therefore can donate to ALL blood types. This blood type is called the universal donor and that is why it is in most demand. The blood type AB+ has all anitgens and therefore won’t raise an immune response to any of the blood types and is called the universal receiver. Canadian Blood Services has a wonderful explanation of the different blood types, who they can donate to and receive from on their website.

For me what makes blood types really interesting is when you start looking at blood components. Blood is largely made up of plasma, red blood cells, white blood cells, and platelets. Red blood cells transport oxygen to the body tissues; white blood cells are immune cells, platelets are cells that are used in clotting, and plasma is the liquid part, that contains the proteins and nutrients in the blood that are required by the tissues in the body. Plasma alone can be used to help individuals with bleeding disorders, liver diseases, and cancers. It can also be used in the production of vaccines or other pharmaceutical products, such as immune globulin used to treat tetanus infections. What is really cool about plasma is that the most in demand blood type for plasma donation is AB+. This is because it is the universal PLASMA donor.

blood donation 45 copy

This might be surprising since above I wrote it is the universal receiver. For whole blood (blood that contains all of the cells and plasma) it is the universal receiver. But once we remove the cells with the antigens leaving only the liquid plasma, it becomes the universal donor. Any antibodies that are present in the blood will be in the plasma, and we know that AB+ won’t form antibodies to any of the blood antigens because it has all three. This means that there will be no antibodies in the plasma that could cause a problem. What is a problem though is that AB+ is the second rarest blood type. Only 2.5% of the population has this blood type. (The rarest blood type is AB- with 0.5% of the population having this type.) I happen to be one of these people, which I have always thought was really cool. The picture on the right is me at my 45th blood donation with Canadian Blood Services.

If you can donate blood, whole or plasma, please do. Not only does it save lives, but it is pretty cool science.