Foundational Discovery · 1901
Discovery of the ABO Blood Groups
Before 1901, surgeons who attempted blood transfusion had no way to predict whether the procedure would save a patient or kill one. Some recipients tolerated infusions from healthy donors without incident; others developed hemolytic crises within minutes and died. The failure was attributed variously to technique, to the donor's temperament, or simply to the mysteries of individual constitution. No one had looked systematically at the blood itself.
Karl Landsteiner changed that with an economical experiment. Working at the Vienna Pathological-Anatomical Institute, he collected serum and red cells from himself and five colleagues, then mixed every possible pairing in small tubes and recorded which produced visible agglutination. The results fell into three reproducible groups, which he labeled A, B, and C in his November 1901 paper in the Wiener klinische Wochenschrift. The C group was later renamed O to reflect its lack of A or B antigens. Two of Landsteiner's colleagues, Alfred von Decastello and Adriano Sturli, extended the work the following year and identified the fourth group, AB, whose cells carry both antigens and whose serum carries neither antibody.
The immunological explanation followed directly from the data. A recipient's serum contains antibodies against whatever antigens are absent from their own cells: type A individuals carry anti-B, type B carry anti-A, and type O carry both. Transfusing the wrong group introduced foreign antigens into a host primed to destroy them. Landsteiner had not simply named groups; he had described a two-component antigen-antibody system that made the outcome of transfusion predictable.
Clinical adoption took time. World War I created enough demand for transfusion that blood group typing became standard practice in military surgical units by 1917, and civilian hospitals followed through the 1920s. Landsteiner received the Nobel Prize in Physiology or Medicine in 1930, by which time his lab had also described the MN and P blood group systems, extending the same analytical framework to additional red cell antigens.
Compatibility testing for red cell transfusion still rests directly on the system Landsteiner described from those six Viennese colleagues. The technique of systematically combining antigen and antibody preparations to map reactivity patterns became the template for blood banking, histocompatibility typing before organ transplantation, and serological forensics. The lasting contribution was methodological as much as practical.
Key People
- Karl Landsteiner — Viennese pathologist who described the A, B, and O blood groups in 1901
- Alfred von Decastello — Co-identified the fourth ABO group (AB) in 1902 with Sturli
- Adriano Sturli — Co-identified the AB blood group in 1902
Wiener klinische Wochenschrift, 1901
Related landmarks
- 1895 · Roentgen's discovery of X-rays (Foundational Discovery)
- 1912 · Funk's vitamine (vital amine) hypothesis (Foundational Discovery)
- 1932 · Identification of vitamin C as the antiscorbutic factor (Foundational Discovery)
- 1861 · Pasteur's refutation of spontaneous generation (Foundational Discovery)