4.5 to 5.5 liters of blood circulates around a person’s body, depending on his or her frame size. However, each person has a distinct composition of the blood, and that is what makes his or her blood type. It then varies depending on the genes inherited from the person’s father or mother.
While there are other approaches for grouping blood types, the best-known and most commonly used is the ABO blood group system. It determines the antigens present in the red blood cells and the antibodies existing in the plasma.
There are four blood types or groups under the ABO system:
A Group: Red blood cells carry A antigens on its surface, while the plasma contains anti-B antibodies.
B Group: Red blood cells carry B antigens on its surface, while the plasma contains anti-A antibodies.
AB Group: Red blood cells carry both A and B antigen, while the plasma contains neither anti-A and anti-B antibodies.
O Group: Red blood cells do not carry A or B antigens, while the plasma contains both anti-A and anti-B antibodies.
However, there are red blood cells that may have the RhD antigen or RhD factor. If they possess such, the blood is regarded as RhD positive, while the absence of the antigen makes the blood RhD negative.
With that, the Rhesus grouping further divides the group system, creating eight main blood types under the ABO/RhD grouping approach: A-, A+, B-, B+, AB-, AB+, and O-, O+.
Here is the distribution of the blood types in the United States.
- A-: 6 percent
- A+: 34 percent
- B-: 2 percent
- B+: 9 percent
- AB-: 1 percent
- AB+: 3 percent
- O-: 7 percent
- O+: 38 percent
But, if ever you find a person needing a blood transfusion, you might probably have heard him asking for donors with a specific blood type. This is because we can’t mix blood types as an ABO incompatibility reaction can occur.
The body’s immune system naturally creates antibodies that combat blood antigens you don’t possess in your own blood. For instance, a person with B-type blood contains anti-A antibodies. If he receives type A or type AB blood, an ABO incompatibility reaction will occur. The anti-A antibodies will reject and destroy the new blood cells.
On the other hand, type O blood does not carry any A or B antigens, making them the ‘universal donor’ type. O-type blood will not be attacked by the receiver’s immune system as there are no antigens present. However, persons with type O blood can also receive type O blood.
Meanwhile, the AB blood does not carry any A or B antibodies but possesses both A and B antigens. Thus, making them the ‘universal recipient type.’ They can accept any red blood cell transfusion as they have both antigens present, avoiding any incompatibility. However, persons with type AB blood can only donate to those who are also AB-type.
It is essential to provide a patient with the correct blood type when undergoing a transfusion. If the wrong blood type is used, it can lead to ABO incompatibility reaction, which can be adverse and possibly fatal.
So, before any blood transfusion procedure, doctors would test a person’s blood to know his blood type. Samples of the recipient and donor’s blood type will then be crossmatched, mixed, and observed for any reaction. Thus, ensuring that such a dangerous consequence won’t occur.
With that, ABO incompatibility reactions remain very rare. Moreover, there are other precautions employed to avoid any mishaps. Doctors and nurses also look out for specific signs while and after the transfusion process that would indicate a reaction and give immediate treatments to minimize adverse effects.
Blood Type (Wikipedia)