A, B, AB, O: What exactly do the different blood types mean and how are they inherited? When it comes to understanding blood types, Patrick’s got you covered.

Being able to access the right type of blood in a medical emergency can be a matter of life or death. But what even is a blood type, and why are they so important?

We didn’t have a system of categorizing blood types until the early 1900s when Austrian doctor Karl Landsteiner came around and developed the organizational system—the well-known ABO blood groups you’ve probably heard of.

Dr Landsteiner traced transfusion complications back to two things: antigens and antibodies.

Antibodies are proteins produced by the immune system that can recognize, investigate, and if needed, destroy an antigen, which is anything that triggers an immune response.

Oftentimes, antigens are viral or bacterial invaders that can cause sickness or infections. Usually your immune system will recognize them and label them as something to attack with antibodies and get rid of in the future.

But other times these antigens are produced by our own bodies, called self-antigens, which our immune system will leave alone.

The entire ABO blood system is built upon these sugar-based self-antigens and corresponding antibodies, and the type of blood you have tells you which kind of antigens and antibodies we’re talking about.

Type A blood means you have A antigens on the outside of the red blood cells and B antibodies in the plasma. Type B blood reverses this, B antigens on the outside of the red blood cell with A antibodies floating around in plasma.

People with AB blood have both A and B antigens, but no antibodies in their plasma while those with type O blood have absolutely no antigens, but have both A and B antibodies.

Then we have that positive or negative symbol that comes after your ABO blood type. That symbol is based on something called the Rhesus Blood Group System, which was named after a monkey species.

Rhesus blood grouping is similar to the ABO system because it too has to do with the presence or absence of an antigen on the outside of the red blood cell — in this case the protein-based Rh antigen.

This is also important when it comes to blood transfusions as a body with Rh negative blood will reject Rh positive blood.

For the most part, everyone in the world has one of these blood types, but why is our blood like this?

Find out the answer and more in this Human.

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Why do people have different blood types?


“For some blood types, evolution and environmental selective pressures are clearly important for their persistence. For example, the Duffy blood type includes a receptor that allows certain types of malarial parasites to enter the red cell.”

Facts About Blood and Blood Types


“Blood types are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body. Since some antigens can trigger a patient's immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching.”

What Happens When You Get The Wrong Blood Type?


“Being transfused with the wrong type of blood is incredibly rare, but it has occasionally happened. What does it feel like to have the wrong type of blood coursing through your veins? It feels like being doomed. Literally.”

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Associated Press 11 May 2020 11:44 CEST

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