Definition
- Blood group antigens (agglutinogens) on the RBC membrane and antibodies (agglutinins) in plasma define blood groups; ABO and Rh are the transfusion-important systems.
- Landsteiner's law: if an agglutinogen is present on the RBC, the corresponding agglutinin is absent from plasma, and vice versa; this fully applies to the ABO system.
ABO Blood Group System
Occurrence of antigens and antibodies in ABO system
Blood group
A
- Antigen (on RBC)
- A
- Antibody (in plasma)
- Anti-B
B
- Antigen (on RBC)
- B
- Antibody (in plasma)
- Anti-A
AB
- Antigen (on RBC)
- A and B
- Antibody (in plasma)
- Nil
O
- Antigen (on RBC)
- Nil
- Antibody (in plasma)
- Anti-A and anti-B
Distribution of antigens and antibodies in the ABO system