‘Give blood. Give now. Give often.’ – World Blood Donor Day


Blood is probably the only liquid on the planet with as many responsibilities as a stressed-out mother with a 2-year-old. Think about it; the contents of blood help transport oxygen and glucose throughout our body, fight disease and gives us healing ‘powers.’ It may sound magical, but what if something as functional as blood could also be the death of you?

Our blood is so diverse that there are a few different varieties that exist; what makes them so different from each other is just a single component; small, complex molecules on the outer surface of the red blood cell membrane called antigens ‘A’ and ‘B.’ These antigens protect red blood cells from destruction by our immune system. Antigens A and B are responsible for our 4 blood groups; A, B, AB and O. But how are 4 blood types obtained from just 2 antigens? And where did the O come from?

This is where we need to take a closer look at our genes. The A and B antigens on our red blood cells are coded for by 3 different alleles (alternative forms of a particular gene); A, B and O. The A and B alleles code for the A and B antigens. The O allele although it exists, is lazy and codes for neither.

Let’s put this into perspective. We inherit one copy of each gene from our parents which gives every individual two alleles determining their blood group. Gene dominance causes one allele from one parent to dominate the other. In blood, the A and B alleles are dominant while the O allele is recessive. For example, if both your parents have type A blood, you will have type A blood, or vice versa. Since O is recessive, you will receive type A blood if you receive alleles A and O.

People with blood group AB are very special because they get the best of both options. If you receive type A and B from your parents, the A and B alleles are both dominant and are expressed together.  Like a race where two people finish at the same time and the 1st prize goes to them both. This genetic phenomenon is called codominance and results in type AB blood. Let’s not forget the O squad! If your parents have type O blood, since the O allele codes for neither A nor B antigens, you will receive type O blood.

Now that everything is understood, how can blood actually be a matter of life and death? Well, when carrying out blood transfusions if someone with type A blood receives type B blood, the antigens in the body that are complementary to type A antigens will reject the B antigens and annihilate them. This is where people with type AB blood are brought back into the lime light because they possess antigens A and B and are universal recipients of blood groups A, B and AB. Those with type O don’t produce any antigens making them universal donors, but reject any other blood type other than O.

But these antigens are insufficient when considering blood donations. Another antigen system called the Rhesus factor (+/-), which determines the presence (+) or the absence (-) of a D antigen on the red blood cell membrane, is why we have +’s and – ‘s for each blood group (A+, A- etc.)

Sri Lanka is among the many middle-income countries that have a blood donation rate of 11.7% per 1000 people. The World Health Organization has witnessed a significant increase in voluntary unpaid blood donations in the past few years. Although blood donations are common, access to safe blood is rare. But it shouldn’t discourage anyone from donating blood and that is why this year’s message encourages you to donate blood because yours could be the reason for someone’s life.

Written by: Sadiya Badurdeen