What happens if you receive blood from the wrong blood group?

Answer

The best-known blood groups are A, B, AB and O. These are the most important, with the most dangerous situations described when they are mixed together. What exactly is happening?

Someone with a blood group A has a certain type of antigen on their red blood cells, the A antigens. Antigens are substances that your immune system responds to. In normal circumstances, your immune system is used to your own antigens and therefore no dangerous reactions occur. If a substance enters the body with foreign antigens, it is normal for the immune system to react to it. This is how the immune system works and can respond to infections from foreign bacteria, viruses, etc.

So if we look back at the person with blood group A, who only has A antigens on his red blood cells, it should be clear that B antigens are foreign to that person’s immune system. So there is a very high chance that the person with blood group A will react violently if blood with blood group B is injected into his veins. That is, the immune system attacks red blood cells with the B antigens, because they are considered invaders. This often triggers fatal reactions.

Someone with blood group AB has both antigens on his red blood cells and has therefore become accustomed to both antigens. Such a person can receive blood from anyone, but only give blood to people with AB.

Someone with blood group O has no A antigens and no B antigens on his red blood cells. They can only receive blood from other people with blood group O, but they can give blood to everyone.

There are other types of blood group subdivisions, such as Rhesus, Kell; this is always about the same principle: the presence or absence of certain antigens on the red blood cells, which, as the recipient body, regards that antigen as an invader, lead to a (sometimes fatal) reaction.