What is the ABO blood classification based on?

The ABO blood classification, also known as the ABO blood group system, is based on the presence or absence of two antigens, A and B, on the surface of red blood cells. These antigens are inherited from both parents and determine a person's blood type.

There are four main blood groups in the ABO system:

- Blood group A: Red blood cells have A antigens only.

- Blood group B: Red blood cells have B antigens only.

- Blood group AB: Red blood cells have both A and B antigens.

- Blood group O: Red blood cells have neither A nor B antigens.

In addition to the A and B antigens, there is also a third antigen called the Rh factor, which can be either positive or negative. This results in eight different blood types: A+, A-, B+, B-, AB+, AB-, O+, and O-.

The ABO blood classification is important in blood transfusions, as it is necessary to match the blood type of the donor and recipient to avoid a transfusion reaction.