Ii antigen system

Ii antigen system is a blood group system that is associated with the Human Leukocyte Antigen (HLA) system. The Ii antigen system is named after the two primary antigens, I and i, which are found on the surface of red blood cells and other tissues.

Antigens

The I antigen is a complex carbohydrate molecule that is found on the surface of red blood cells and other tissues. It is a part of the HLA system and plays a role in the immune response. The I antigen is present in high amounts in adults, but its levels decrease with age.

The i antigen is a simpler form of the I antigen. It is present in high amounts in newborns and decreases as the individual matures. The i antigen is also found on the surface of red blood cells and other tissues.

Antibodies

Antibodies to the I and i antigens are naturally occurring and can be found in the plasma of individuals who do not have the corresponding antigens on their red blood cells. These antibodies can cause hemolytic disease of the newborn (HDN) if a pregnant woman with I or i antibodies is carrying a fetus with the corresponding antigens.

Clinical significance

The Ii antigen system has clinical significance in transfusion medicine and organ transplantation. In transfusion medicine, it is important to match the Ii antigens of the donor and recipient to prevent transfusion reactions. In organ transplantation, matching the Ii antigens can help to prevent graft rejection.

See also

• Blood group system
• Human Leukocyte Antigen
• Hemolytic disease of the newborn
• Transfusion medicine
• Organ transplantation