Blood Typing

Experiments with blood transfusions, the transfer of blood or blood components into a person's blood stream, have been carried out for hundreds of years. Many patients have died and it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups, that blood transfusions became safer.

Mixing blood from two individuals can lead to blood clumping or agglutination. The clumped red cells can crack and cause toxic reactions. This can have fatal consequences. Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells.

Karl Landsteiner's work made it possible to determine blood groups and thus paved the way for blood transfusions to be carried out safely. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.

What is blood made up of?

An adult human has about 4–6 liters of blood circulating in the body. Among other things, blood transports oxygen to various parts of the body.


Blood consists of several types of cells floating around in a fluid called plasma.

The red blood cells contain hemoglobin, a protein that binds oxygen. Red blood cells transport oxygen to, and remove carbon dioxide from, the body tissues.

The white blood cells fight infection.

The platelets help the blood to clot, if you get a wound for example.

The plasma contains salts and various kinds of proteins.

What are the different blood groups?

The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules. The blood group you belong to depends on what you have inherited from your parents.

There are more than 20 genetically determined blood group systems known today, but the AB0 and Rh systems are the most important ones used for blood transfusions. Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.

Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.


AB0 blood grouping system

According to the AB0 blood group system there are four different kinds of blood groups: A, B, AB or 0 (null).

Blood group A

If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma.


Blood group B

If you belong to the blood group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma.


Blood group AB

If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma.


Blood group 0

If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma.


Blood typing – how do you find out to which blood group someone belongs?

A person with A blood receives B blood. The B antibodies (yellow) in the A blood attack the foreign red blood cells by binding to them. The B antibodies in the A blood bind the antigens in the B blood and agglutination occurs. This is dangerous because the agglutinated red blood cells break after a while and their contents leak out and become toxic.

Blood transfusions – who can receive blood from whom?

People with blood group 0 Rh - are called "universal donors" and people with blood group AB Rh+ are called "universal receivers."

Of course you can always give A blood to persons with blood group A, B blood to a person with blood group B and so on. But in some cases you can receive blood with another type of blood group, or donate blood to a person with another kind of blood group.

The transfusion will work if a person who is going to receive blood has a blood group that doesn't have any antibodies against the donor blood's antigens. But if a person who is going to receive blood has antibodies matching the donor blood's antigens, the red blood cells in the donated blood will clump.

Blood Group Antigens Antibodies Can Give Blood to Can Recieve Blood From
AB A and B None AB AB, A, B, O
A A B A and AB A and O
B B A B and AB B and O
O None A and B AB, A, B, O O

You are to answer the following questions in your books

1. What are the main consituents of blood?

2. State the four main blood groups?

3. Define the term agglutination, and explain why it happens when incompatible blood types are mixed together?

4. Distinguish between antigens and antibodies?

5. Draw up an agglutination table?

6. If a person's blood agglutinates with anti-A serum, what possible blood types could they be?

7. Define the term UNIVERSAL DONOR and UNIVERSAL RECIPIENT, and state the blood types that relate to each term.

8. Using a punnett square list the possible genetic make up of the four blood types (eg. type A can be AA or AO)

9. Why is it impossible to get type O blood unless you have two O genes?

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