Why blood transfusion? – Blood transfusion is sometimes required in patient management for various reasons. In such cases, the blood group of the patient and the donor are very important. This is to avoid transfusion reaction which occurs when the wrong blood group is transfused into a patient.

However, sometimes, the right blood for a particular patient may not be available whereas there is a compelling need to give blood to a patient. Here comes the concept of universal donor and universal recipient.

Components of Blood

To understand the concept of having the right blood, we look at blood groups and what they contain. Blood has two major components: the solid components (red blood cells, white blood cells and platelets) and the liquid component (plasma).

The red blood cells are the main concern when blood is to be transfused. They have antigens on them while the plasma contains antibody. For the purpose of understanding, a brief explanation of antigens and antibodies will help.

Antigen – An antigen is a substance that causes the body to produce an immune response (defence) against the substance. This may be a toxin, chemical, virus, bacteria, body cell, body tissue etc.

Antibody – An antibody is a substance (protein) made by white blood cells, which allows the body to make specific immune response (defence) to an antigen. Each antibody is specific as it binds to only one antigen in order to destroy it.

The following are the major blood groups that are regularly screened for and what they contain in terms of antigen and antibody:

1. Group A – The red blood cells have A antigen while the plasma has anti-B antibody. This means it will accommodate group A cells but antagonise group B cells carrying B antigen.
2. Group B – The red blood cells have B antigen while the plasma has anti-A antibody. This means it will accommodate group B cells but antagonise group A cells carrying A antigen.
3. Group AB – The red blood cells here have both A and B antigens and no antibody. It means it will accommodate both group A and group B cells since it does not have any antibody to attack either of them. This group of people are loosely referred to as universal recipients. 
4. Group O – The red blood cells here have no antigen while the plasma has both anti-A and anti-B antibodies. This means they it will attack red blood cells with either A or B antigens. However, as the people in this group have no antigen on their red blood cells, the red blood cells can easily evade attack from any antibody from the recipient of the blood. They are therefore loosely referred to as universal donor.

Rhesus Blood Factor

For Rhesus blood factor, Rhesus D factor is the most significant and most commonly screened for. Those who have the D antigen on their red blood cells are said to be Rhesus D positive (A+, B+, AB+ or O+) while those without the D antigen on their red blood cells are said to be negative (A-, B-, AB- or O-).

Those with Rhesus negative blood can give blood to both Rhesus positive and negative of the same group. For example, blood group A- can be transfused to someone with blood group A+ or A- whereas those with Rhesus negative red blood cells should receive Rhesus negative blood except in the face of life-threatening emergency.

The Danger of Universality in Blood Transfusion 

Universal donor – When someone with blood group O donates blood, the red blood cells do not have antigen while the plasma has anti-A and anti-B antibodies. If this blood is given to someone with blood group A (for example), in the name of universal donor, the anti-A antibody in the plasma of the donor blood will attack and destroy the red blood cells of the recipient.

However, because the quantity of blood transfused, in most cases, is far less than the total blood volume of the recipient, the recipient’s plasma effectively dilutes the plasma in the transfused blood to the extent that its effects become almost negligible. If the transfusion involves large quantity of blood, the dilution effect may be overwhelmed, leading to destruction of the red blood cells of the recepient. 

Universal recipient

People with blood group AB are usually referred to as universal recipient. This is because they have A and B antigens. So, they can receive blood from group AB (with A and B antigens), group A (with A antigen), group B (with B antigen) and group O (with no antigen). However, there is a little problem when they receive blood from any other group other than AB.

If they receive blood from blood group A, the plasma has anti-B antibody which will attack the B antigen on the recipient’s red blood cells. If they receive from blood group B, the plasma has anti-A antibody that will attack the A antigen on the recipient’s red blood cells. If they receive blood from group O, the plasma has both anti-A and anti-B antibodies directed against A and B antigens on the recipient’s red blood cells.

Though the volume of blood transfused may be little compared to the quantity of blood volume in the recipient thereby minimizing the effects of the antibodies by successfully diluting them; when large volume of blood is transfused, the quantity of the antibodies may be large enough as to cause significant destruction of the red blood cells in the recipient and therefore making the transfusion counterproductive.

Conclusion

Except in dare emergencies that involve life and death, blood transfusion for any patient should be group-specific. In emergency situation, where arrangement is being made to get blood of appropriate blood group ready, the concept of universal donor or universal recipient may be applicable to save life.

Routine transfusion of blood of different blood groups under the guise of universal donor or universal recipient should be discouraged as much as possible.