First day of the commemorative stamp for the 125-year anniversary of the discovery of blood groups

Not all blood is the same

The classification of the four blood groups A, B, AB and O was a groundbreaking medical discovery that has played a vital role in modern medicine and saved countless lives.

The Austrian physician and immunologist Karl Landsteiner (1868–1943) observed that blood sometimes clumped when samples from different individuals were mixed. Through systematic research, he discovered in 1900 that there were different blood groups: A, B and C – the latter now known as blood group O. Shortly thereafter, the fourth group, AB, was identified. These blood groups are defined by the presence of specific antigens – molecular structures on the surface of red blood cells – against which antibodies are produced in the blood of individuals with incompatible blood types. People with blood group O are considered universal donors, as their red blood cells carry no A or B antigens, while those with blood group AB have both antigens and are considered universal recipients. The stamp illustration displays recipients at the top and donors on the left. Landsteiner published his findings in a medical journal in 1901.

In recognition of his discovery of blood groups, Karl Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930. He also played a key role in identifying the Rhesus factor in 1940, another important element in blood transfusion compatibility, and contributed significantly to research on polio and syphilis. Today, 14 June – his birthday – is observed as World Blood Donor Day. Blood donations remain essential, as there is still no substitute for human blood.

Special post office: 14 June 2025, 11:30 a.m. to 5:30 p.m., Westfield Donau Zentrum, Wagramer Straße 94, 1220 Vienna

Blood Donor Day: Post am Rochus, Rochusplatz 1, 1030 Vienna

Group pictures:
Picture of presentation: © Ö. Post AG
Picture 1 (left to right): Walter Oblin, CEO, Austrian Post, Peter Kaiser (Deputy Secretary General, Austrian Red Cross)