60 Fun Facts About Blood Types

Blood types are defined by antigens on the surface of what?

The antigens can be proteins, carbohydrates, glycoproteins or glycolipids depending on the blood group system.

Which two blood group systems matter most when matching blood for a transfusion?

Together they give the familiar labels such as A+, O- or AB+.

How many human blood group systems did the ISBT recognise as of 2025?

A truly complete blood type would describe a person's status in every one of the 48 systems recognised by 2025.

Which blood group has neither the A nor the B antigen on its red cells?

Its plasma carries both anti-A and anti-B antibodies, which is why it can only receive from its own group.

People with which ABO group are known as 'universal recipients' for red cells?

Their plasma has no anti-A or anti-B antibodies, so red cells from any group are tolerated, but they can only donate to their own group.

Which blood type is called the 'universal donor' for red cell transfusions?

Because it can go to anyone in an emergency, it is often overused and almost always in short supply.

What kind of antibodies are the naturally occurring anti-A and anti-B in human plasma?

They are thought to develop in the first years of life through exposure to food, bacteria and viruses.

What letter did the discoverer of the ABO groups originally use for the group now called O?

His 1901 scheme was A, B and C; the C was later replaced by O.

The letter O in the ABO system was chosen to stand for a German word meaning what?

Some scientists preferred the numeral zero, and in many languages the group is still called 0.

Which group was discovered a year after the first three, by his students Sturli and von Decastello?

They did not even give it a name at first, calling it 'no particular type'.

In which year did Karl Landsteiner make his definitive observation of blood-group agglutination?

He had noticed the clumping (agglutination) the year before, even between human and animal blood.

The discoverer of blood groups won the Nobel Prize in Physiology or Medicine in which year?

He had by then emigrated to New York to work at the Rockefeller Institute.

Besides blood groups, the discoverer of the ABO system co-discovered which virus in 1909?

He worked with Constantin Levaditi and Erwin Popper on the discovery.

World Blood Donor Day, held on 14 June, marks the birthday of whom?

The World Health Organization has celebrated it on that date since 2005.

Which Czech serologist independently described four blood types in 1907, numbering them I to IV?

His system was preferred in much of Europe while an almost identical American scheme by Moss confusingly reversed I and IV.

Which pair of physicians introduced the O designation in 1910, later adopted internationally?

The League of Nations' standardisation commission endorsed their naming in 1928.

A 1919 paper in The Lancet by the Hirszfelds was the first to show what?

They had typed thousands of soldiers of many nationalities on the Macedonian front.

Who demonstrated in 1924 that ABO groups are inherited as multiple alleles at a single locus?

The correct inheritance pattern settled decades of confusion about how types pass from parents to children.

The 'Rh' in Rh factor was originally short for what?

The name is now considered a misnomer, since the human antigen turned out to differ from the monkey one, but it stuck.

How was the serum that led to the discovery of the Rh factor produced?

It reacted with about 85 percent of human red cells, which became the Rh-positive majority.

Which Rh antigen is the most important, because it most often provokes an immune response?

The + or - after your ABO letter refers only to this one antigen out of about 50 in the Rh system.

Roughly what share of Europeans lack the RhD antigen, compared with about 0.3% of Asians?

The gap creates supply problems for Rh-negative Westerners needing blood in East Asia.

Which European people have the highest recorded frequency of blood lacking the D antigen, over 47%?

Rh negativity means the RHD gene is missing or mutated.

The extremely rare Rhnull phenotype, lacking every Rh antigen, has been nicknamed what?

It has been identified in fewer than 50 people, though that figure is often misread as the number alive today.

When hemolytic disease of the newborn is fatal to the fetus, what is the condition called?

It classically arises when a D-negative mother forms anti-D antibodies after carrying a D-positive baby, and they attack a later pregnancy.

What injectable medication stops mothers who lack the D antigen from forming anti-D antibodies?

It is on the WHO List of Essential Medicines and is usually given at about 28 weeks and again after delivery.

People with the Bombay (hh) blood phenotype form antibodies against which antigen found on nearly all red cells?

They can only safely receive blood from other Bombay-phenotype donors, and the trait occurs in about 4 people per million.

The Bombay phenotype is far more common in its namesake city, at roughly what rate?

Worldwide the figure is closer to 4 per million.

Lacking the Duffy antigen gives resistance to which disease?

The antigen is the receptor Plasmodium vivax uses to enter red cells, so Duffy-negative blood is common where the parasite is endemic.

The Duffy antigen is named after what?

Richard Duffy was a haemophiliac who had received many transfusions and developed the first anti-Fya antibody in 1950.

The Kell antigen is sometimes associated with which X-linked condition?

In McLeod phenotype the Kell antigens are poorly detected in lab tests.

What common medical procedure can permanently change a person's ABO blood type?

Once the recipient's own stem cells are destroyed, all new red cells come from the donor and carry the donor's antigens.

Which blood group reaches its highest frequency in the Middle East?

It is thought to have been entirely absent from Native American and Australian Aboriginal populations before European contact.

Which blood group was thought absent from Native Americans and Australian Aboriginals before Europeans arrived?

Group A, by contrast, reaches some of its highest frequencies among Australian Aboriginal groups and the Blackfoot people of Montana.

Which group of German soldiers had their blood group tattooed on them during World War II?

The tattoos were meant to speed emergency transfusions but later helped identify SS members.

Who performed the first transfusion of animal blood into a human, in June 1667?

He was physician to Louis XIV; six months later Richard Lower gave a Londoner sheep's blood before the Royal Society.

James Blundell performed the first successful human transfusion in 1818 to treat what?

He used the patient's husband as donor, taking four ounces of blood with a syringe at Guy's Hospital.

Which Chicago doctor coined the term 'blood bank' when he set up a hospital blood store in 1937?

He was director of therapeutics at Cook County Hospital.

Soviet surgeon Sergei Yudin pioneered transfusions in 1930 using blood from what source?

He reported his first seven cadaveric transfusions to a surgeons' congress in Kharkiv that September.

What size does the WHO define as one 'unit' of donated whole blood?

India uses 350 mL units and Japan 200 or 400 mL.

In the United States, how long must a donor wait between whole-blood donations?

Platelet donors can return after only a week.

What is the refrigerated shelf life of donated red blood cells?

Platelets last only days, which is why supply is a permanent headache for blood services.

What is the most common reason a would-be donor is turned away?

The check makes sure giving blood will not leave the donor anaemic.

The belief that blood type predicts personality is especially widespread in which part of the world?

Scientists dismiss it as pseudoscience, but it shapes dating, hiring and even bullying in Japan.

Who published 'The Study of Temperament Through Blood Type' in Japan in 1927, launching the idea?

The militarist government even commissioned a study on breeding ideal soldiers; the idea was revived by journalist Masahiko Nomi in the 1970s.

What is 'bura-hara' in Japan?

The word is a portmanteau of 'blood' and 'harassment' and has been blamed for playground bullying and lost jobs.

Which naturopath's 1996 book Eat Right 4 Your Type popularised the blood type diet?

Dietitians and physicians agree there is no scientific evidence the diet improves health.

What is the scientific consensus on the blood type diet?

A 2017 review found no clinical evidence that it improves health.

Which blood group system was named for the patient Kelleher, in whom the antibody was found in the 1940s?

Antibodies to its K antigen can cause severe haemolytic disease of the newborn.

The ABO antigen also sits on which clotting protein, linking group O to slightly faster bleeding?

Group O people have lower levels of the protein, and it is broken down faster.

Genome-wide studies have linked variants at the ABO gene to susceptibility to which cancer?

Loss of A and B antigen expression is also a common event in many carcinomas.

ABO blood groups exist in which other animals?

Other species have entirely different blood group systems of their own.

Plasma from which blood group can be transfused to patients of any ABO group?

Plasma compatibility is the inverse of red-cell compatibility: AB plasma carries neither anti-A nor anti-B, yet AB patients can only receive AB plasma.

In a typing test, what visible reaction shows that an antigen is present on the red cells?

A blood sample is added to solutions of antibodies for each antigen; where the cells clump together, the matching antigen is present.

Which American physician's 1910 numbering of blood types was adopted in Britain, France and the US?

His I and IV were the reverse of the Czech system already in use elsewhere in Europe, a dangerous confusion that lasted until letters replaced numerals.

Which blood group system did Landsteiner discover with Philip Levine in 1927?

The pair found the P system the same year, after Landsteiner had moved to the Rockefeller Institute in New York.

Which 1945 laboratory development helped lead to the discovery of many more blood groups?

Together with the rise of transfusion medicine and understanding of ABO haemolytic disease of the newborn, it pushed the count toward today's 48 systems.

Fresh frozen plasma is quick-frozen to preserve which two labile clotting factors?

It is given to patients with potentially fatal clotting problems, such as advanced liver disease or an anticoagulant overdose.

What is thought to trigger anti-A and anti-B antibody production in early life?

These naturally occurring antibodies are usually IgM, and they are why a mismatched transfusion reacts immediately.

In many languages other than English, group O is commonly written as what?

Landsteiner himself first labelled the group C, and it was never clear whether the later O meant the figure 0 or the German ohne, 'without'.