Have You Ever Wondered Why People With Different Blood Groups Can't Donate To Each Other?


We all know that it is lethal for people from different blood groups to give blood to each other, but we have very little knowledge of the cause of it. Today, we're going to try to learn what causes this deadly transfer and why people have different blood types. It seems as though evolution has a part in this.

Our blood groups have a special characteristic that can cause destruction in the wrong body.


Why do people have more than one blood group? The answer given by scientists to this question is that people evolved in the past having different blood groups to develop immunity against different infectious diseases.

For example, those with blood groups O and B have higher resistance to malaria than other blood groups.


Blood groups O and B provide an evolutionary advantage, such as on the African continent where deaths caused by malaria are high. Because cells that are infected by malaria can't hold much in the O and B type blood cells, people with these blood groups become less sick if they catch malaria.

How are blood groups classified?


This classification is based on the presence or absence of two antigens A and B on our red blood cells. Another classification is the positive-negative classification according to the presence or absence of Rh factor in our blood.

There are millions of antigens on every red blood cell.


Antigens are the names given to the things our immune system can respond to. If the antigens in the new blood that enter our bodies are different from those of our bodies, our immune system starts attacking these new red blood cells. These aggressors are known as antibodies and the type of our antibodies can be Anti-A and Anti-B according to our blood group. Antibodies are molecules produced by our immune system that protects our bodies against bacteria and viruses, and these molecules can also be produced in response to different blood groups that are perceived in the body.

Rh factor is a special protein found in the blood cells of 85% of people.


And as you can imagine, people with Rh factor in the blood cells have Rh +, while those who do not have Rh factor have Rh- blood type. Rh tests are especially important for women during pregnancy; Because if the mother has Rh- and the baby has a Rh + blood group, the mother's immune system will start to produce antibodies and attack the baby, seeing the baby as a foreign substance.

From this point of view different blood groups can be explained as follows:

  • Blood group AB individuals have both A and B antigens on the surface of their RBCs, and their blood plasma does not contain any antibodies against either A or B antigen. Therefore, an individual with type AB blood can receive blood from any group (with AB being preferable), but cannot donate blood to any group other than AB. They are known as universal recipients. 

  • Blood group A individuals have the A antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the B antigen. Therefore, a group A individual can receive blood only from individuals of groups A or O (with A being preferable) and can donate blood to individuals with type A or AB.

  • Blood group B individuals have the B antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the A antigen. Therefore, a group B individual can receive blood only from individuals of groups B or O (with B being preferable) and can donate blood to individuals with type B or AB.

  • Blood group O (or blood group zero in some countries) individuals do not have either A or B antigens on the surface of their RBCs, and their blood serum contains IgM anti-A and anti-B antibodies. Therefore, a group O individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB). If a patient in a hospital situation needs a blood transfusion in an emergency, and if the time taken to process the recipient's blood would cause a detrimental delay, O negative blood can be issued. Because it is compatible with anyone, O negative blood is often overused and consequently is always in short supply. According to the American Association of Blood Banks and the British Chief Medical Officer’s National Blood Transfusion Committee, the use of group O RhD negative red cells should be restricted to persons with O negative blood, women who might be pregnant, and emergency cases in which blood-group testing is genuinely impracticable.

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