Wednesday, March 26, 2025

Why do blood types have to be A, B, AB, and O? Why not just A, B, C, and D?

 Yes, why is that? I used to ask the same thing. Why aren't blood types simply named A, B, C, and D? Do adults just like to complicate things?

To find out why blood types are named out of order, we have to go back more than a century.

Before 1900, people (including those in the medical world) thought that all human blood was the same. Before the 20th century, although humans already knew that blood was a vital component for the body, we still didn't know much about what was contained in blood itself. As a result, various things related to blood and processes involving blood—including blood transfusions—were shrouded in myths.

Because of this ignorance, many blood transfusion attempts ended in failure and death. In fact, we didn’t even know that humans could receive blood from other humans until 1818! Before that, there were attempts to donate human blood from animals such as dogs, cows, and goats.

Sir James Blundell, the first person to successfully perform a human-to-human blood transfusion in 1818.

Finally, in 1900, Mr. Karl Landsteiner conducted an experiment on human blood. Mr. Karl found that mixing blood from other humans could also cause clotting. This clotting is what causes blood transfusions to fail.

After conducting further experiments, in 1901 Mr. Karl classified blood into three types, namely type A, type B, and type C. The formula is:

  • Type A blood will clot when mixed with type B, but will not clot when mixed with other type A blood.
  • Type B blood will clot when mixed with type A, but will not clot when mixed with other type Bs.
  • Type C blood clots when mixed with either type A or B.

In his article, Mr. Karl wrote that there are possibly two types of agglutinogens (the concept of agglutinogens was also first proposed by Mr. Karl), namely agglutinogen A and B. Agglutinogen A is found in type A blood; B is found in type B blood; both are found in type C blood.

Next, Mr. Karl discovered that blood has antibodies, which react to agglutinogens. These antibodies are called anti-A and anti-B. In type C blood, there are no agglutinogens contained. However, type C blood contains both anti-A and anti-B.

In the following year, two of Karl's students, Adriano Sturli and Alfred von Decastello , discovered a fourth blood group, but it was not named.

Finally, in 1910, Ludwig Hirszfield and Emil Freiherr von Dungern, two scientists from Poland and Germany, decided to give names to each blood type that had been discovered.

  • Type A is named blood type A, because it contains agglutinogen A. The name of the agglutinogen itself comes from the first Greek letter, alpha.
  • Type B is named blood type B, because it contains agglutinogen B. The name of the agglutinogen itself comes from the second Greek letter, beta.
  • Type C is called blood type O (zero or null ) because it does not contain any agglutinogen. The original name of this group is 0 (zero) but in its development it was named O to make it easier to pronounce.
  • The unnamed type, discovered by Mr. Karl's two students, was named AB blood type, because it contained both A and B agglutinogens.

In fact, Hirszfield and von Dungern could have given the designation A, B, C, and D to these blood types. However, to make it easier to remember the agglutinogens, the names were made according to the agglutinogens. This will also make it easier for people to understand and remember the concept of which blood types can be donated to whom and who cannot donate to whom.

If there are people who research blood further and want to keep the ABCD designation, it is still possible (remember, blood types are not only the ABO system. There are others, such as the MN and Rhesus systems). The important thing is that the person must have a strong basis for why they classify blood into ABCD. If the ABCD system turns out to have various advantages compared to the ABO system, then it is not impossible that the ABCD system will replace the ABO system.