Today’s Factismal: There are over 300 different human blood types.
In case you haven’t seen the public service announcements, January is National Blood Donor Month. Every year, 4.5 million Americans need a blood transfusion; that works out to be about 43,000 pints (enough to fill 10,173 two liter bottles or three Olypmic-size swimming pools each year). Because blood must be used within 42 days, the Red Cross and other centers are always looking for donors. But the most fascinating thing about blood donation is that it wouldn’t have happened before 1907, just over a century ago.
That’s because blood consists of plasma (55%), red blood cells (40%), white blood cells (3%), and platelets (2%). Of these, the most important component for blood donation is the red blood cells. Not just because it is the red blood cells that carry oxygen from the lungs to the cells and carbon dioxide from the cells to the lungs, but also because the red blood cells are covered with proteins that interact with the plasma (more specifically, with the serum). If the proteins on the red bloods cells match those in the plasma, then the blood moves normally. But if they don’t match, then the red blood cells form clumps and clots. When this happens in a test tube, it is annoying; when it happens in a person, it is usually fatal.
But if you knew which proteins were present in the blood, you’d be able to take blood from one person and put it into another person with similar proteins. And that is exactly what Karl Landsteiner discovered in 1901 – that most people have red blood cells that are covered with one of three different sets of proteins. He called them “groups A, B, and C”; this was changed into A, B, and O by later workers. And just six years later, in 1907 the first successful blood transfusion took place in New York.
Many people would have been tempted to rest on their laurels. Not Dr. Landsteiner. He continued to research blood groups, and discovered the M, N, and S groups (which are secondary proteins that influence how well the A and B proteins work) and helped to refine the Rh factor. He also discovered the polio bacillus, which led to the March of Dimes campaign to eradicate the disease, and was the first person to cultivate typhus, which has led to important advances in treatment. For his contributions to medical science and especially for his discovery of blood groups, Landsteiner was awarded the 1930 Nobel Prize in Medicine.
Today, Landsteiner’s work is the basis for safe and reliable blood donations. When you donate blood, a drop of it is tested to see which blood type you have. Do you have the protein that reacts with everything but A type blood? Do you have the protein that reacts with everything but B type? Do you have both proteins (AB)? Or are you lacking both (O)? And does your blood react with Rh factor (Rh positive)?
|Blood Type||Rh Factor||How many have it?|
|O||+||1 person in 3|
|O||–||1 person in 15|
|A||+||1 person in 3|
|A||–||1 person in 16|
|B||+||1 person in 12|
|B||–||1 person in 67|
|AB||+||1 person in 29|
|AB||–||1 person in 167|
For the vast majority of the population, the four main blood types (O, A, B, AB) and the Rh factor (+, -) are enough to define our blood type; most of us can use blood from one of those eight groups. But some people have strong M, N, S proteins or other factors that prevent them from using anyone else’s blood. The only way to find out where you fit is to go donate blood today!