Blood type namely group A, group B, and group C. He defined that group A blood agglutinates with group B, but never with its own type. Similarly, group B blood agglutinates with group A. Group C blood is different in that it agglutinates with both A and B. This was the discovery of blood groups for which Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930. (C was later renamed to O after the German "Ohne", meaning without, or zero, or null.) The group AB was discovered a year later by Landsteiner's students Adriano Sturli, and Alfred von Decastello.
Jehovah's Witnesses and blood transfusions who are Jehovah's Witness would not administer blood transfusions to fellow dedicated members. As to administering transfusions to non-members, "The Watchtower" stated that such a decision is "left to the Christian doctor's own conscience." In 1982, a "Watchtower" article declared that it would be wrong for a Witness to allow a leech to feed on his/her blood as part of a medical procedure, due to the sacredness of blood. In 1989 "The Watchtower" stated, "Each individual must decide" whether to accept hemodilution and autologous blood salvage (cell saver) procedures. In 1990, a brochure entitled "How Can Blood Save Your Life?"