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A single drop of blood contains thousands of white blood cells, millions of platelets and many millions of red blood cells.
These cells make up about 45% of your blood. The remaining content is a substance called plasma.
But it’s your red blood cells that determine your blood type.
WHAT’S YOUR TYPE?
There are eight main blood types: A+, A-, B+, B-, AB+, AB-, O+ and O-.
Red blood cells have molecules called antigens on their cell surface. The most well-known blood types are determined by the A, B and Rh factor D antigen (the + or – next to your letter).
A person’s red blood cells can have A antigens, B antigens, both A and B antigens or neither!
If your red blood cells have the D antigen on them, you’re assigned the + symbol. If you don’t, your blood type will end in the – symbol.
Credit: Ali Damouh/Science Photo Library/Getty Images
ANTIGEN ALERT!
White blood cells are another type of cell present in your blood. While there are only around 10,000 of these in a single drop of blood, they pack a punch!
White blood cells are part of your immune system. They keep you safe from the invaders that could make you sick.
White blood cells can see antigens on these invading pathogens and make antibodies to neutralise the threat. The trouble is that, to a white blood cell, any foreign antigen looks threatening.
While white blood cells won’t make antibodies against the antigens on your own red blood cells, they will make antibodies against the other red blood cell antigens.
For example, white blood cells in a person with B blood type won’t fight B antigens, but they will fight A antigens.
This is why blood transfusions and blood donations are so carefully managed. If you receive the wrong type, your white blood cell antibodies will target those donor red blood cells for destruction. A disaster!
A DIFFERENT INHERITANCE
Your blood type is inherited from your parents – one set of genes from each. Because of this, the most common blood type varies by population.
If you’re one of the 7% of Aussies who have O- blood, you are pretty special! Your red blood cells can be donated to anyone because there are no antigens on your red blood cells, so it won’t react badly with the recipient’s own blood.
Credit: Drew Kendell
The good news is that Australians are generous with their blood, no matter their type.
Each year, Lifeblood collects around 1.6 million blood donations – that’s equivalent to over 750,000 litres.
But while nearly 60% of us are eligible to donate blood, only 3% do.
If you like the idea of rolling up your sleeve and becoming a lifesaver, consider becoming a blood donor.
