ABOveriryhmien

ABOveriryhmien refers to the ABO blood group system, the classification of human blood based on the presence or absence of A and B antigens on the surface of red blood cells. The system is determined by three alleles, IA, IB, and i, located on chromosome 9. IA and IB are codominant, while i is recessive. Individuals with IAi express type A, IBi express type B, IAIB express type AB, and ii express type O. The plasma of people with type A or B contains antibodies against the other antigen (anti-A or anti-B), whereas type AB individuals typically have no anti-A or anti-B antibodies.

These antibodies can cause immune reactions if incompatible blood is transfused, making ABO compatibility critical in transfusion medicine. In red blood cell transfusions, type O negative is often called the universal donor, while type AB is the universal recipient. For plasma transfusions, AB plasma is considered the universal donor because it contains no anti-A or anti-B antibodies. ABO antigens can also be expressed in other tissues and secretions, and secretor status influences whether a person expresses these antigens outside the blood.

Subgroups exist within the main types, such as A1 and A2, and rare variations can complicate transfusion decisions. Variation in ABO distribution is observed across populations and can have epidemiological relevance for disease associations and transplantation.

History and significance: the ABO system was first described by Karl Landsteiner in 1900, establishing a foundational concept in transfusion medicine and immunohematology.