Blood Typing Tutorial

Created by Shawn Snaples

There are 4 different blood types: A, B, O, and AB. How does your body know which blood type you are? There are antigens, or markers, on the outside every cell. There are antigens that say "I am a red blood cell", "I am type A blood", and even antigens that say "I am me." Bacteria have antigens that say "I am a bacteria." So any given cell could have lots of different antigens.

Type A red blood cells have A antigens. Type B red blood cells have B antigens. Type AB blood has both A & B. Type O blood has, guess which antigen? Type O blood is special. Type O red blood cells do not have any blood type antigens at all. The lack of the antigen tells your body that it must be Type O blood.

Blood Type	A	B	AB
O
Antigens	A	B	A, B	none

During WWI, soldiers got shot and were bleeding to death. Somebody got the idea of giving these dying soldiers donated blood. So they took some blood from nurses and other soldiers, and they gave the blood to the dying soldiers. Some soldiers did not have any problems with the blood. But others died. Their bodies did not like the new blood. Their immune system attacked it. But it did not seem to matter who got which blood. It was not that the blood from the compassionate female nurses worked better than blood from other soldiers. Or that German blood did not work in Americans.

Looking back, we know that the problem was that the soldiers were getting the wrong blood type. We know is had nothing to do with the personality of the donor; but at the time, the doctors did not know why some soldiers died and others did not. It turns out that it has to do with these antigens that we have been talking about. If you have type A blood, your body does not like the other blood types. It makes antibodies against the antigens on other blood types.

It turns out that it has to do with these antigens. Your body doesn't like the other blood types. There are antibodies against the antigens on other blood types; these antibodies are present since before birth. When we study the immune system, we'll find that for most things your immune system has to encounter the problem antigen, then make antibodies for next time. ABO blood antigen are weird because you are born with them. The first time you are exposed to a wrong blood type, your body attacks it.

The antibodies will attack the antigens. And your immune system will destroy the foreign blood cells. This is what was happening to the soldiers. They were getting the wrong blood type. Their immune system was upset because it found foreign blood. And it would attack it. Antibodies attack and clump together blocking blood vessels. This incompatibility kills the person, even faster if they weren't in such good shape to begin with.

Hemolysis is when the blood bursting from incompatible blood types.

If you are given type B blood, your B antibodies will attack the B antigens of the new blood. When the antibodies attack the antigens, it forms a big complex that is too large to fit through your capillaries and you will die from it. This is what was happening to the soldiers. Some of them were getting the wrong blood type. Their immune system was upset because it had found foreign blood. And their immune system attacked the foreign, incompatible blood. The incompatible blood kills the recipient. The soldiers who were surviving the blood transfusions, by sheer luck, had been given a compatible blood type

So if you have type A antigens, type A blood, your body does not like type B blood. Your body will make type B antibodies.

If you have type B blood, with B antigens, your body will make A antibodies.

If you have type AB blood, you have both A & B antigens. If your body were to make A antibodies, they will attack the A antigen on your red blood cells. So you cannot make A antibodies. Similarly, if your body were to make B antibodies, they will attack the B antigens on your red blood cells. You cannot make B antibodies. So if you have type AB blood, your body cannot make any blood type antibodies.

What about type O? You do not have any antigens on your red blood cells. So your body can make both A antibodies and B antibodies. Type A, B, and AB blood are foreign, and your body does not like any of them, so you make antibodies to both A & B.

Blood Type	A	B	AB
O
Antigens	A	B	A, B	none
Antibodies	B	A	none	A, B

So what blood type can you receive? If you are type A, you can receive a transfusion of type A blood. You can also get type O. Type O does not have any antigens, so your body can not make any antibodies to it. You can only make antibodies to antigens that are present. Type O blood has no blood type antigens. So you can receive type O blood.

If you are type B, you can get type B and type O. What about type AB? Your body has A antibodies which will attack the A antigens on AB blood. So you cannot get Type AB blood.

If you are type AB, you do not have any antibodies, so you can receive any blood type: A, B, O, or AB.

If you are type O, you have A antibodies, so you cannot get type A or AB. You have type B antibodies, so you cannot receive type B or type AB blood. All you can get is type O blood.

Blood Type	A	B	AB
O
Antigens	A	B	A, B	none
Antibodies	B	A	none	A, B
Receive	A, O	B, O	A, B, AB, O	O

In addition to all these blood types, there is what is called an Rh factor. Rh was first discovered in Rhesus monkeys, so they called it Rh. Your Rh type is either + or -.

If you are Rh+, then you have a + antigen on your red blood cells, but you cannot make antibodies because they would attack your blood.

If you are Rh-, then you do not have an Rh antigen, and your body can make antibodies to the Rh+ antigen.

People who are Rh+ can receive + or - blood because they don't have any antibodies to attack the Rh antigen. People who are Rh- can only get - blood because their Rh+ antibodies will destroy any Rh+ red blood cells.

Type O- is known as the universal donor. Type O- can be given to any person with any blood type because the O blood has no antigens and Rh- type has no antigens. It does not matter what blood type the recipient is because type O- blood has no antigens for antibodies to attack.

Type AB+ is known as the universal recipient. People who are AB+ can get any blood type of either Rh factor. People with type AB+ blood do not make any antibodies to any of the blood types, so they can receive any blood type: A+, A-, B+, B-, O+, O-, AB+, or AB-

How can we use this information? Scientists have made synthetic antibodies to the A antigen, the B antigen, and the Rh+ antigen. We simply mix a few drops of blood with a few drops of each of the synthetic antibodies in a special tray. If the antigens on the blood react with the synthetic antibodies, the blood will clot. If other antigens are on the red blood cells, they will not react with the antibodies and the blood will not clot. This information will give us the blood type of the sample so that we can avoid giving someone an incompatible blood type.

When we are typing blood, we are looking for clotting. That's backward from when giving people blood transfusions. In blood transfusions, we don't want clumping. We do not want antibodies attacking antigens because that kills the recipient. But in blood typing, we are looking for clotting in the correct well. If you have clotting in the A well, then the blood has type A antigens on it. If you have clotting in the B well, then the blood has type B antigens. If you have clotting in the Rh well, then the blood is Rh+. If there isn't clotting in a particular well, then the blood doesn't have that antigen.

For example, if we mix type A+ blood with A antibodies, B antibodies, and Rh+ antibodies, the A antibodies will attack the A antigens on the blood and clot. The Rh+ antibodies will attack the + antigens on the blood and it will clot. There are no B antigens for the B antibodies to react with, so the blood will not clot.

What blood type is this?

Right O+. O does not have any antigens for the A or B antibodies to attack, so they don't clot. But it does have an Rh+ antigen and the Rh+ antibodies will attack it.

Now you are ready for your next assignment. Today you are going to determine some blood types. Dallas police need your help to solve a murder. They have some blood from the victim, some blood that was found at the crime scene, and blood from 4 suspects. Two drops of blood were mixed with 2 drops of each of the synthetic antibodies; the results are shown below. Determine the blood type of each of the blood samples.

This is blood from the victim. What blood type is it?

This is blood found at the scene of the crime. What blood type is it?

What blood type is Suspect #1?

What blood type is Suspect #2?

What blood type is Suspect #3?

What blood type is Suspect #4?

Which suspect is still a suspect?

Does this prove he did it?

No, it just says that the blood types match, but it does not even prove that it was blood from our suspect. It only says that the blood at the scene is the same blood type, not the same person.



If you have any questions or comments, please e-mail Shawn Snaples.

Date Last Modified: 8-9-02