What is this ABO anyway?
Blood transfusions date back to the middle ages where first attempts were unsuccessful, but due to modern medicine and extensive research blood donations are now a standard procedure.
In the beginning of the 19th century four different blood types were discovered. Later, in the middle of the 19th century, the Rhesus factor, another antigen (protein) covering the red blood cells, was found in the Rhesus Macaque (monkey) and named after it. Depending on the existence of the antigen the blood group is divided into Rhesus factor positive or negative. In middle Europe 85% have the antigen, and have Rhesus positive blood, 15% are Rhesus negative. In Asia the ratio is very different with only 1% of the population having Rhesus negative blood (rh-); in fact only 0.3% of Thais are rh-.
The ABO System shows four major groups: A, B, AB, O. The letter refers to the antigens attached to the red blood cells. People with the blood group A have the antigen type A and vice versa. For blood group AB both antigens types are found. On the other side blood group O has no antigens. Therefore adults have antibodies against the missing antigens.
The existence of antigens and antibodies plays a crucial role for transfusions of whole blood or blood plasma because the incompatibility between the different blood types. Mixing these different blood types can result in clotting, which can lead to death.
Someone with the blood type O tolerates only whole blood type O, while someone with the blood type AB tolerates all other types. Those with type A blood tolerate type O and A (adequately for type B). Consequently type O could be considerate as universal blood, because it is tolerated by all other groups.
However it is different for plasma transfusions; looking at the plasma transfusion the circumstances are contrary to the whole blood transfusion.
People with group AB can only receive plasma from donors from the same type. People with type O on the other side can receive plasma from all donors.
Someone with type A could receive plasma from donors with blood group A and AB (adequately for B).
Formerly the blood types were used to determine parentage because the blood group factors are hereditary.
For the Allele factor, which is a gene member producing different traits in a genes characteristics, A and B are dominant for over Allele O, therefore it is impossible if a child has blood group O if one of the potential parent has AB blood. But since the emergence of genetic testing, blood group testing to determine parentage is rarely used.
Rhesus-System/ Rhesus Factor
The Rhesus factor indicates a protein on the cell membrane of the red blood cells. The Rhesus system contains six main antigens. The most important though is the D-Antigen, which can cause massive immune reactions.
A person with Rhesus factor-D-Antigen is classified as Rhesus positive (RhD positive), if the antigen is missing it is classified as Rhesus negative (RhD negative).
The Rhesus factor has special significance for pregnant women with RhD negative and if the unborn has RhD positive. For these cases the mother has antibodies against the Rhesus factor of the fetus, which can lead to disabilities or death.
RhD positive blood transfused repeatedly to a person with RhD negative blood can result in transfusion incidents. The antibodies destroy the red blood cells in Rhesus positive carrier (fetus or transfusion). Consequences can be
anaemia, due to the destruction of the red blood cells,
Icterus, if the red blood cells are destroyed Bilirubin builds up,
and liver and kidney swelling as well as general edema.