ABO Blood Group System:

It is the most important blood group system in humans. It was discovered by the Austrian scientist Karl Landsteiner, who found four different blood groups (blood types) in 1900. He was awarded the Nobel Prize in Medicine for his work.

Classification of ABO Blood Group System:

In this system, four different blood groups are distinct from each other based on specific antigens (antigen A and B) present on the surface of RBCs.

• Group A:

A person having antigen A has blood group A.

• Group B:

A person having antigen B has blood group B.

• Group AB:

A person having both antigens has the blood group AB.

• Group O:

A person having none of the A and B antigens has blood group O.

Rh Blood Group System (+ve & -ve blood group system):

In the 1930s, Karl Landsteiner discovered the Rh-blood group system. In this system, there are two blood groups i.e., Rh⁺ and Rh^- which are distinct from each other based on antigens called Rh factors (first discovered in Rhesus monkey), present on the surface of RBCs.

• Rh-positive:

A person having Rh factors has blood group Rh-positive.

• Rh-negative:

A person not having Rh factors has blood group Rh-negative.

Note:

Unlike the naturally occurring anti-A & anti-B antibodies of the ABO system, an Rh-negative person does not produce anti-Rh antibodies unless he or she is exposed to Rh-factor.