Science · Medicine & the body

Blood groups

ABO discovered 1901

Medicine — immunohaematology and transfusion

Classifications of blood according to the inherited antigens carried on the surface of the red cells. Karl Landsteiner found in 1901 that mixing blood from different people sometimes made the cells clump, and sorted them into the classes now called A, B and O, with AB added by his students the following year; in 1940 he and Alexander Wiener identified the Rhesus system. Because the body carries antibodies against the antigens it lacks, transfusing the wrong type causes agglutination and potentially fatal haemolysis — which is why transfusion only became safe once the types were known.

How to spot them

▸Karl Landsteiner, 1901, and the Nobel Prize of 1930
▸A, B, AB and O, each either positive or negative for the Rhesus D antigen
▸O negative is the universal red-cell donor; AB positive the universal recipient
▸Antigens sit on the red cell; the matching antibodies float in the plasma
▸The Rhesus system is named after experiments using rhesus macaque red cells

Key facts

Karl Landsteiner's discovery of 1901, which won him the Nobel Prize in Physiology or Medicine in 1930 (1901)

He originally labelled the classes A, B and C; C was renamed O

Experiments with rhesus macaque red cells in 1940, and the D antigen they revealed (1940)

Landsteiner and Alexander Wiener; the D antigen is what 'positive' and 'negative' refer to

O negative is the universal donor of red cells; AB positive the universal recipient

O negative cells carry none of the A, B or D antigens

Haemolytic disease of the newborn, and the anti-D injection given to prevent it

A D-negative mother can make antibodies against a D-positive foetus

The rare phenotype first described in Bombay in 1952, lacking even the H antigen (1952)

The Bombay phenotype (hh), which types as O but cannot receive ordinary O blood

Jan Janský's four Roman-numbered classes of 1907 (1907)

An independent classification that briefly competed with Landsteiner's letters

Kell, Duffy, Kidd, Lewis and MNS — among the 48 systems the ISBT now recognises

ABO and Rh are only the two that matter most clinically

Antigens on the red cell membrane, matched by antibodies in the surrounding fluid

The basic mechanism: agglutination when antigen meets its antibody

Key ideas

The rule is that you carry antibodies against whatever antigens you lack, so group O — with neither A nor B antigen — has both anti-A and anti-B, and group AB has neither.
Red cells and plasma follow opposite rules: O negative is the universal red-cell donor, while AB is the universal plasma donor.
Lacking the Duffy antigen confers resistance to the malaria parasite Plasmodium vivax, which is why Duffy negativity is near-universal in much of West Africa.

Quick-fire facts

•Karl Landsteiner described the ABO system in 1901 and received the 1930 Nobel Prize in Physiology or Medicine
•He labelled the classes A, B and C; C became O. AB was identified in 1902 by his students Alfred von Decastello and Adriano Sturli
•The Rhesus system was described in 1940 by Landsteiner and Alexander Wiener, using antisera raised against rhesus macaque red cells
•'Positive' and 'negative' refer to the presence or absence of the RhD antigen
•Group O has anti-A and anti-B antibodies; group AB has neither, and is therefore the universal recipient of red cells
•O negative is the universal red-cell donor; AB is the universal plasma donor
•In the UK, O positive is the commonest type at roughly 35 per cent of donors and AB negative the rarest at about 1 per cent
•The ABO gene lies on chromosome 9; the RHD and RHCE genes on chromosome 1
•The Bombay phenotype (hh), described by Y. M. Bhende in 1952, lacks the H antigen and can only receive blood from another Bombay donor
•The International Society of Blood Transfusion recognised 48 distinct blood group systems as of 2025, including Kell, Duffy, Kidd, MNS, Lewis and Lutheran
•Anti-D immunoglobulin, given to RhD-negative mothers, prevents haemolytic disease of the newborn
•The Czech serologist Jan Janský published a rival four-class system in 1907, numbered I to IV

Drill it — 8 cards

1 / 8new card

Sources

NHS Blood and Transplant — Blood types
The Nobel Foundation — The Nobel Prize in Physiology or Medicine 1930