If you remember your first-year biology or genetics, you may also recall the name “Landsteiner,” for it was Karl Landsteiner (1868-1943) who discovered the famous A, B, and O blood groups. And, in much of the world today—but not in the U.S.—Google is celebrating his 148th birthday with this Doodle:
These four blood groups represent combinations of three alleles, an A, a B, and an O allele (the A blood type is AA or AO, the B blood type is BB or BO, the AB blood type is AB, and the O blood type is the double recessive OO). The genetics were not worked out by Landsteiner, nor did he know that the alleles code for antigens: glycoproteins on the surface of the red blood cell. A has one antigen, B another, and O has neither. That means that ABs are the “universal recipients”, since they don’t produce antibodies to the A and B alleles, and can get anybody’s blood, while Os are the “universal donors”, since they express no antigens at all and don’t stimulate the immune system to reject the donor blood. If you’re an O, like I am, your blood is the most useful of all four types. But if you have the additional “negative” Rh type, you’re even more useful (I’m O positive), because there’s incompatibility of Rh types, too. Know your blood type, and put it in your passport and in your wallet. The rules above are a guideline, as there can still be some incompatibility, so doctors often do a cross-check by mixing bloods before transfusion. But in an emergency they rely on the ABO and Rh rules.
At any rate, although Landsteiner didn’t know the genetics and biochemistry, he did know which blood mixed with which without agglutination, and this led to the first successful blood transfusion based on Landsteiner-group compatibility in 1907. (Note to Wikipedia: this was not the first recorded and successful human-to-human transfusion; that was done in 1818 by James Blundell.)
It’s not well known that Landsteiner, along with Erwin Popper, also discovered and isolated the polio virus—in 1908.
For the blood-group discovery Landsteiner received the Nobel Prize in Medicine and Physiology in 1930.

I have no idea why this Doodle isn’t seen in the U.S.:
h/t: David W.














