In 1902 Landsteiner, an Austrian born American immunologist, announced one of the major medical discoveries of the century, that of the ABO blood group system. His work permitted successful blood transfusion, and the saving of so many lives. He was over 70 when in 1940 he announced the discovery of the rhesus (Rh) factor, then responsible for the serious illness or death of 1 in 200 white babies.

Landsteiner also introduced dark field microscopy for the diagnosis of primary syphilis and with several associates worked on the characteristics of Spirochaeta pallida . They were able to describe the mechanism that resulted in the Wassermann reaction. Together with Ernest Finger and others he discovered that the antigen, previously extracted from a syphilitic human, could be replaced with an extract prepared from ox hearts for this test.

For more than a decade between 1908 and 1922 Landsteiner performed research in poliomyelitis. He injected a preparation of brain and spinal cord tissue obtained from a polio victim into a Rhesus monkey, which later developed paralysis. Further work led him to conclude that a virus caused the disease. Later, in cooperation with the Pasteur Institute he developed a serological test for the diagnoses of the disorder.

Landsteiner received the Nobel Prize in physiology or medicine in 1930 for his discovery of human blood groups. Austria honoured him philatelically in 1968 on the 100th anniversary of his birth (Stanley Gibbons 1525, Scott 813).