ABO blood group system best of 2022

The ABO blood group system is one of the known categorizations of the blood everyone is expected to know.

Before we can understand the peculiarities in the different blood groups, we will have to understand the basics of the system.

This classification is based on the immunological response between antigen and antibody as inherited by the red blood cells. These antibodies can also be referred to as agglutinogens.

This is because they have the capacity to cause agglutination (lumping of blood cells) of the red blood cells. Blood showing type A antigen on the surface of their cells naturally have the ability to attack type B red blood cells, resulting in agglutination.

Now this means that if blood from type B red blood cells is transfused into a Type A carrier, the transfused blood will be destroyed by the recipient’s Type A antibodies. Likewise when the scenario is repeated anti-clock-wisely.

The reason why this happens is that for every antigen present on the surface of the RBCs, their corresponding agglutinin must be absent in their serum.

Overview of the ABO blood group system

To explain this further, if antigen A is found on the surface of an RBC, the agglutinin for A must not be found in the serum of the cell or If a particular antigen is absent in the RBCs surface, the corresponding agglutinin must be present in the serum.

This explains the reason why blood type A will not destroy transfused blood type A, rather it will destroy any other one apart from O.

The ABO blood group system (antigens) is well developed well before birth and remains throughout an individual’s life existence.

ABO blood group system  by idealmehealth

There is no doubt that the ABO blood group system is acquired passively from mothers to children before childbirth. The children actively by the age of three months should start generating their own antigens.

ABO blood group system is categorized based on the presence or absence of antigen A and antigen B on the RBC surface.  ABO blood group system is divided into four groups:

  • ‘A’ group
  • ‘B’ group
  • ‘AB’ group
  • ‘O’ group

Blood having antigen A belongs to the group ‘A’. This blood has B-antibody inside the serum. Blood with antigen B on the cellular surface and A –antibody inside its serum belongs to the ‘B’ group.

If both the antigens A and B are present on the surface of the cell, the blood group is referred to as the ‘AB’ group, and the serum of this group does not contain any antibody ( agglutinogen). If both Antigens A and B are absent, the blood group is called group ‘O’  and both A and B antibodies(agglutinogens) are present inside the serum of the RBC.

Importance of ABO blood group system

When blood is been transfused, only compatible blood must be given. The ‘donor’ is the one who gives blood while the ‘recipient’ is the one who receives the blood being transfused.

Before transfusion of blood is made, special considerations concerning the antigen of the donor and the antibody of the recipient are to be factored in. In most cases, the antibody of the donor and antigen of the recipient are ignored leading to preventable death.

RBC of ‘O’ group has no antigen on their surface and so agglutination does not occur with any other group of blood. With this, blood group   ‘O’ can be given to any other blood group persons and the people with this blood group are referred to as ‘universal donors’.

The serum of AB group blood has no antibody. Therefore it does not cause agglutination of RBC from any other group of blood in the case of blood transfusion. People with the AB group can receive blood from any other blood group persons.  Therefore, people with this blood group are mostly referred to as ‘universal recipients’.

abo blood group system by idealmedhealth
abo blood group system

What happens when the wrong red blood cell is transfused to a recipient?


A hemolytic transfusion reaction occurs when the red blood cells given during transfusion are destroyed by the recipient’s immune system.

They are the adverse reactions in the body, which occur due to transfusion error that involves transfusion of mismatched blood.

These reactions may be mild causing only fever and skin disorder characterized by itching or may even slip to the severity of the case leading to renal failure, shock, and eventually to death.

If there is a mismatch in transfusion, reactions occur between the donor’s RBC and the recipient’s serum. So, if the donor’s serum contains agglutinins (antibody) against the recipient’s RBC, agglutination will not occur. This is because the donor’s antibodies are diluted in the recipient’s blood.

However, if the recipient’s serum contains agglutinins against the donor’s RBCs, the immune system launches a response against the new blood cells.

Therefore, donor RBCs are agglutinated (blood cells are clumped together) resulting in transfusion reactions.

We want to believe that, to an extent, we have done great justice to this topic; the ABO blood group system.

With this knowledge, I believe we have come to note how important it is for us to know the group to which our antigen is classified. This will enable swift and safer decision-making in case of emergencies that will demand blood transfusion.

ABO blood group system chart

Below the image is the ABO blood group chart that shows the compatibility of the different blood groups.


FAQs on the ABO blood group system

How many blood groups are in the ABO blood group system?
There are 4 main blood groups that are determined by gene as explained above namely; A, B, AB, and O.
What do you mean by ABO blood group system?
ABO blood group system is the classification of human blood based on the gene properties of red blood cells on the presence or absence of the A and B antigens.

Conclusion on the ABO blood group system

The ABO blood group system is an important classification of the red blood cell which are very important in determining many health factors about life.
The discovery of the ABO blood group, over 10 decades, caused great excitement. Until then, all blood had been assumed to be the same, and the often tragic consequences of blood transfusions were not understood.  Thus one of the great impacts of this discovery on mankind.


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