Karl (karl). 1868–1943, Austrian immunologist, who discovered (1900) human blood groups and introduced the ABO classification system. He also discovered (1940) the Rhesus (Rh) factor in blood and researched into poliomyelitis. Nobel prize for physiology or medicine (1930)
Austrian-born American pathologist who discovered the human blood groups A, B, and O in 1901. In 1902, his colleagues discovered a fourth group, AB, and in 1927 Landsteiner discovered two more groups, M and N. For this work Landsteiner received the 1930 Nobel Prize for physiology or medicine. In 1940 he discovered the Rh factor.
