ABO Blood Grouping – History, Genes Responsible and Principle

History of Blood Grouping

1900: Karl Landsteiner's Breakthrough

• Austrian immunologist Karl Landsteiner discovered that mixing blood from different individuals could cause agglutination (clumping of red blood cells).

• In 1901, he classified human blood into three groups: A, B, and C (later renamed O). This was the birth of the ABO system.

1902: AB Blood Group Identified

• Landsteiner’s colleagues, Alfred Decastello and Adriano Sturli, discovered the AB blood group, completing the four-type system: A, B, AB, and O.

Genes Responsible

• The ABO locus is located on chromosome 9 at 9q34.1-q34.2. It contains 3 alleles i.e. IA, IB and IO or (i), O being recessive and A and B as Dominant alleles.

• For A/B antigen synthesis to occur, a precursor called the H antigen must be present.

• The H gene, located on chromosome 19 (locus 19q13.3), encodes an enzyme called fucosyltransferase (FUT1).

Formation of Antigens – A, B and O

Genes Responsible

Principle of Blood Grouping

• The principle of blood grouping is rooted in the concept of agglutination, a reaction between antigens on red blood cells (RBCs) and antibodies in plasma.

• Antigens (also called agglutinogens) are specific molecules found on the surface of RBCs.

• Antibodies (agglutinins) are proteins in the plasma that recognize and bind to foreign antigens.

• When matching antibodies encounter their specific antigens, they bind and cause clumping (agglutination) of RBCs.

• This clumping is visible and forms the basis for identifying blood groups.

Landsteiner’s Law

First Law (Universal Principle)

• If an agglutinogen (antigen) is present on red blood cells, the corresponding agglutinin (antibody) will be absent in the plasma.

• Example: A person with A antigen on RBCs will not have anti-A antibodies in plasma.

Second Law (Specific to ABO System)

• If an agglutinogen (antigen) is absent on red blood cells, the corresponding agglutinin (antibody) will be present in the plasma.

• Example: A person without B antigen will have anti-B antibodies.

  Rh Typing Principle

• Based on presence of D antigen (Rh factor) on RBCs.

• Anti-D serum is used:

• Agglutination → Rh Positive

• No agglutination → Rh Negative

ABO Blood Grouping- History, genes responsible and Principle