What makes O so special?

By Lauren Hoskin

A new technology is emerging that may be able to overcome transfusion problems. This could eradicate the constant demand for ever-depleting stocks of blood type O, and result in all blood donations being equally useful. The technique uses an enzyme extracted from coffee beans to convert all blood types into the universally accepted O. So what makes O so special?

The ABO system consists of 4 groups. These groups are determined by the presence of an antigen on the surface of blood cells. There are two types of antigen, A and B. Blood type A express antigen A, and blood type B express antigen B. Blood type AB unsurprisingly express both antigens, and blood type O express neither.

Whilst the blood cells express antigens, cells of the immune system called plasma cells may also be expressing antibodies. Antibodies act as receptors that detect antigens and mediate the killing of anything seemingly foreign- a very useful system for fighting disease. Not so useful however when transfusing foreign blood. In type A individuals the plasma cells express anti-B antibodies which will attack any transfused blood cells expressing B antigens, and vice versa. In blood type AB individuals, no antibodies are expressed seeing as both A and B are natives.  In people with blood type O, antibodies are expressed to both A and B, meaning that O recipients can only accept from O donors.

Blood transfusions between incompatible types results in the recipient’s antibodies forming an attack on the donated blood, causing life threatening immune haemolysis. So the lack of antigen expression makes O particularly special as it will never be detected as foreign, and so can be given to people of all blood types.

Furthermore, it is the most common blood type; held by around 44% of the UK population. This means 44% can ONLY accept O, and the other 56% will all accept O as well as their own, making demand high.

A technology such as the ECO-RBC (Enzyme Converted group O Red Blood Cell) method would massively relieve strains on blood supplies, making all blood universally transferable. This method is the most advanced, however it has not yet been verified as safe, so the pressure is on!