Junior blood group system

Junior blood group system is a human blood group system that is recognized by the International Society of Blood Transfusion (ISBT). The system is named after a patient, "Mrs. Junior", in whom the first antibody was discovered. The Junior blood group system is relatively rare and is not routinely tested for in blood transfusions.

History

The Junior blood group system was first identified in 1952 by Landsteiner and Wiener, who discovered an antibody in the serum of a pregnant woman, Mrs. Junior, that reacted with the red blood cells of her husband and 85% of random donors. This led to the identification of the Junior blood group system.

Genetics

The Junior blood group system is determined by a single gene, ABCG2, located on chromosome 4. The gene encodes a protein called ATP-binding cassette sub-family G member 2 (ABCG2), which is a member of the ATP-binding cassette (ABC) transporter superfamily. Mutations in this gene can lead to the absence of the Junior antigen on red blood cells.

Antigens

The Junior blood group system consists of two antigens, Jr^a and Jr^b. Jr^a is a high-frequency antigen, found in more than 99.9% of people, while Jr^b is a low-frequency antigen, found in less than 1% of people. The presence or absence of these antigens determines a person's Junior blood group.

Clinical significance

The Junior blood group system is not routinely tested for in blood transfusions, as the Jr^a antigen is present in almost all individuals. However, in rare cases, individuals may produce alloantibodies against the Jr^a antigen, which can cause hemolytic disease of the fetus and newborn (HDFN) and hemolytic transfusion reactions (HTR).

See also

• Blood group system
• ABO blood group system
• Rh blood group system

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  Diagram illustrating autosomal recessive inheritance.