Blood carries oxygen around the body, removes carbon dioxide and helps us fight off infections.
This combination of antigens and antibodies determine which blood type you can be safely given for medical purposes.
Antibodies are produced by white blood cells and used by the immune system to identify and attack foreign substances in the body.
Blood group antigens are found on the surface of red blood cells and are ignored by the immune system. But antigens of another blood type will be seen as foreign, and attacked by antibodies.
Blood group A has A antigens on the red blood cells with anti-B antibodies in the plasma.
The other common (and important) type of blood classification is the Rhesus or Rh blood group system.
But not all blood is the same, and is classified into different types or groups.
B antigen (attached to red blood cell)
A antigen (attached to red blood cell)
Blood is made up of red blood cells, white blood cells, and platelets held in a liquid called plasma.
Blood group B has B antigens with anti-A antibodies in the plasma.
White blood cells fight infections.
Blood group AB has both A and B antigens, but no antibodies.
Both the ABO and the Rh blood types are important when it comes to matching blood types for transfusion.
Platelets help the blood to clot.
The Rh group has 50 defined blood-group antigens, but the most important from a classification and blood compatibility point of view is the RhD antigen.
Blood group O has no antigens, but has both anti-A and anti-B antibodies in the plasma, as well as some special “anti-A,B” antibodies.
If you were mistakenly given type-B blood, which contains B antigens, the anti-B antibodies in your plasma will identify it as foreign and attack the introduced blood, resulting in potentially fatal consequences.
It’s a very complex system, and many “partial” or variant antigens exist, but generally speaking, if the RhD antigen is present, then your blood group is RhD positive.
Anti-B antibodies attack the foreign B antigens
For example, if your ABO group is type B, and you are RhD positive, then you would be classed as having B positive or B+ blood.
The chart below shows the blood type compatibility for blood donors and receivers.
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The specific combination of these components determines an individual's type in most cases.
Red blood cells carry oxygen around the body and remove carbon dioxide.
There are over 30 known blood systems, though the two main ones are the ABO and the Rh group.
For example, if you have type-A blood, you will have the A antigen on the surface of your red blood cells, and also the anti-B antibody in your plasma.
The ABO classification is the most important and relevant for blood compatibility.
What are blood types?
A small number of antigens and antibodies are responsible for the ABO blood types.
Our blood group is determined by the presence or absence of specific antibodies and antigens in our blood.
We all have a specific blood group, which is inherited from our parents in the same way we inherit other traits (such as eye colour).
Our bodies have about four to six litres of blood flowing in our veins and arteries.
Anti-B antibodies attack the B antigens on the foreign blood.
There are over 30 known blood group systems, though the two main ones are the ABO and the Rh group.
Blood group O has no antigens, but both anti-A and anti-B antibodies in the plasma, as well as some special “anti-A,B” antibodies.