Born June 14, 1868 - Vienna
. Died June 24, 1943 - New York
For hundreds of years, research into blood transfusions was done in fits and starts, beginning with disastrous 17th century experiments between humans and various animals. By the 19th century, doctors basically understood that human blood was absolutely necessary for human transfusions, but even then the chance for success was frustratingly random.
As an immunologist in Austria, Dr. Landsteiner observed in the late 1800s that in some cases, the human body rejected other people's blood just as violently as if the blood were from an animal. By 1901, Landsteiner had discovered the existence of four distinct blood groups, and that blood samples from two incompatible groups could not safely integrate. When he named these groups A, B, AB, and O in 1909, his revolutionary findings finally got the attention they deserved.
The disruption of World War I sent Landsteiner to a research stint at a Dutch hospital before he wound up at the prestigious Rockefeller Institute for Medical Resarch. In 1930, Landsteiner finally received the Nobel Prize for physiology or medicine, and stayed at the Rockefeller Institute until his death in 1943.