Blood groups ABO and the D antigen of the blood decides for a successful transfusion process. The blood groups has a type of antigen on its surface which decides over the group. There are some other types of groups according which the blood is again classified. They are the
Kell system
, the
MNS system
and the
Lewis system
. But most commonly used is the
ABO group system
.
ABO Blood Group
- If Antigen A is present, then it is called Group A. When Antigen B are present, then they are named as Group B. At times, both A & B type of antigens are present on the surface, then the blood group is named as Group AB. But when neither Antigen A nor B is present, the group is called Group O.
- The anti-A antibodies and the anti-B antibodies are naturally found in the plasma. These are needed for the natural defence mechanism of our body.
- Antigen A present in the Blood Group A can recognise Antigen B as a foreign molecule. When it is exposed to the Blood Group B, the body produces anti-B antibody to destroy the foreign molecule.
- The Antigen B present in the Blood Group B can recognise Antigen A as a trespasser and hence produce antibodies to destroy it.
- So when a person with Blood Group A is transfused with Blood Group B, his body gets sensitized. Anti-B antibodies are produced to kill the antigens and destroy the blood cells.
- No antibodies are formed with Blood Group AB because they have both the antigens in them. So they do not produce any antibodies in defence.
- Blood Group O do not have either Antigen A or Antigen B. So this group can be donated to any blood type. Since no antigens are present, so no antibodies will be produced. Blood Group O is considered as ‘universal donors’. They can produce anti-A antibodies when exposed to Blood Group A and produce anti-B antibodies when exposed to the Blood Group B.
- When an opposite antibody is produced inside a body, it can be life-threatening.
Rh-D System
Similarly, our blood has another antigen called the D antigen on its surface. This decides on the Rh factor of the blood. ‘Rh’ stands for ‘Rhesus’. This type of protein was first identified in the Rhesus monkeys. Hence the name originated. This protein or antigen decides if a person is Rh +ve or Rh -ve. When a person lacks the D-antigen in its blood, he is said to have Rh-ve blood. When a person has the D-antigen it its blood, then he is said to have Rh+ve blood. About 80% of people worldwide are Rh +ve while the remaining 15% are Rh -ve.
- The blood group of a person is defined by the blood group and the RhD group.
- Someone with Blood Group Ab and Rh +ve is said to be AB +ve.
When someone has a blood group O with Rh -ve, then he is said to be O -ve.
Chart To Show The ABO Blood Group Distribution.
| Blood Group | Percentage Of People |
|---|---|
| O | 44 |
| A | 42 |
| B | 10 |
| AB | 4 |
Chart To Show The ABO Blood Group Distribution.
| Blood Group | RhD Type | Percentage Of People |
|---|---|---|
| O | Positive (+ve) | 37 |
| O | Negative (-ve) | 7 |
| A | +ve | 35 |
| A | -ve | 7 |
| B | +ve | 8 |
| B | -ve | 2 |
| AB | +ve | 3 |
| AB | -ve | 1 |
My blood was tested many years ago [~50] as O Rh” and said to be rare.
ie: Rh+ Donor , but a Rh- recipient , as I ‘lack the D antigen’.
The puzzle is-
If I lack this D antigen, why is my blood considered positive when used on others -as this D is the very factor causing the blood to be ‘positive’ normally?