81 Fun Facts About Blood Types

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

Red cells: ABO antigens also coat many other body tissues, so a mismatch can also provoke an immune reaction against a transplanted organ.

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

ABO and Rh: ABO antibodies form naturally in early childhood, so even a first transfusion of the wrong ABO type can trigger a deadly reaction.

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

48: most matter little day to day, because antibodies against them are far less likely than ABO or Rh ones to cause a transfusion reaction.

Whose 1628 book describing the circulation of the blood made the idea of transfusion possible?

William Harvey: showing that blood travels round the body in a closed loop suggested it could be passed from one animal into another.

In 1665, physician Richard Lower pioneered blood transfusion by passing blood between two of which animal?

Dogs: two years later he gave a man sheep's blood in front of the Royal Society.

Which blood type is often called the 'universal donor'?

O negative: hospitals reach for it in trauma and emergencies, when there is no time to find out a patient's own blood type.

What can very rarely make a patient with group A blood briefly test as a different group?

A severe infection: enzymes released by some microbes can turn the A antigen into a B-like one, so such patients should not be given blood carrying B.

What letter did Karl Landsteiner first use for the blood group now called O?

C: within a few years, doctors were using these groups to match donors to patients, making transfusion far safer.

The O in the ABO blood group system is often said to stand for a German word meaning what?

Without: the German 'ohne' suits a group lacking both antigens, though some early researchers wrote it as the figure 0, for zero.

From 1914, doctors added sodium citrate to donated blood to stop it doing what?

Clotting: kept liquid this way, donated blood could be stored for longer before being given to a patient.

Besides guiding transfusions, Karl Landsteiner's blood groups were used by lawyers in which kind of case?

Paternity suits: blood groups pass from parents to children by fixed rules, so a mismatch could rule a man out as a child's father.

After World War I, the discoverer of human blood groups left Vienna and later worked in which American city?

New York: after a spell at a small hospital in The Hague, he joined the Rockefeller Institute, where he later helped find the Rh factor.

Besides blood groups, Karl Landsteiner also co-discovered which virus?

Polio: he showed the disease could be passed on to monkeys, proving that it could spread.

Which wartime blood policy did blood-bank pioneer Charles Drew publicly criticise as unscientific?

Segregating donated blood by race: the armed forces first had Black donors turned away, then accepted their blood only if it was kept apart.

Canadian surgeon Norman Bethune set up a mobile blood transfusion service during which war?

The Spanish Civil War: his unit drove bottled blood to wounded soldiers near the front lines.

An AB parent and an O parent usually have children with which blood groups?

A or B: the AB parent passes on either A or B, while the O parent passes on O, which both A and B mask.

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

Rhesus: the human antigen later proved different from the monkey's, but the name had already spread, so it was simply shortened to Rh.

Landsteiner and Wiener discovered the Rh factor using serum from which kind of immunised animal?

Rabbits: their serum reacted with the blood of most people tested, who became known as Rh-positive.

Rh disease, when an Rh-negative mother's antibodies attack her baby's blood, usually strikes which of her pregnancies?

A later pregnancy: her antibodies usually form after the first baby's blood mixes with hers at birth, then attack a later Rh-positive baby.

Which European people have the highest recorded frequency of Rh-negative blood?

The Basques: a puzzle, since before modern medicine the trait's link to a deadly newborn blood disease worked against its carriers.

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

Golden blood: lacking Rh proteins, its cells are misshapen and fragile, so they break down sooner than normal ones.

Why did US blood banks for years refuse donors who had lived in Britain between 1980 and 1996?

Mad cow disease: its human form, variant CJD, can be passed on through blood transfusions.

What 1960s advance largely prevents Rh disease, in which a mother's antibodies attack her baby's blood?

An injection given to the mother: it is thought to stop her immune system from reacting to Rh-positive cells leaked from the baby.

Lacking the Duffy antigen gives resistance to which disease?

Malaria: the Duffy protein is the doorway the parasite Plasmodium vivax uses to invade blood cells, so cells lacking it resist infection.

The Duffy antigen is named after what?

The patient in whom it was found: Richard Duffy, a haemophiliac given many transfusions, had formed antibodies against his donors' antigen.

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

A bone marrow transplant: the donor's stem cells take over making blood, so once the patient's old cells die off, the new ones carry the donor's type.

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

Frontline Waffen-SS: after the war, Allied screeners made German soldiers raise their arms to check for the tattoo, and SS men were held or arrested.

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

Jean-Baptiste Denys: after a later patient died, he faced court action, and France soon banned such transfusions.

James Blundell pioneered transfusing human blood in the 19th century to treat what?

Bleeding after childbirth: seeing how often it killed his patients, he set out to find a remedy.

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.

A standard whole-blood donation is closest in volume to which everyday measure?

A pint: that single donation is often split into separate products, such as plasma and platelets, for different patients.

Refrigerated donor blood keeps for about six weeks, so how can rare blood types be stored for years?

By freezing it: the cells are first treated with glycerol to protect them, letting blood banks keep rare types for many years.

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

Low haemoglobin: each donation removes iron the body needs to make haemoglobin, so donors whose levels test too low are asked to wait.

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

East Asia: in Japan, the belief took off after journalist Masahiko Nomi began writing popular books about it in the 1970s.

What does 'bura-hara', a term tied to blood-type personality beliefs, describe?

Discrimination by blood type: the term blends 'blood' and 'harassment', and such prejudice has been blamed for bullied children, lost jobs and broken relationships.

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

Peter D'Adamo: his theory casts type O as the ancestral group, so it prescribes type O people a meat-heavy diet like that of hunter-gatherers.

The 'blood type diet' casts type A as the blood of early farmers, so which diet does it prescribe for type A?

A vegetarian diet: dietitians say any benefit comes from eating more healthily, not from matching meals to blood type.

Which animal's main blood group system sorts individuals into types A, B and AB?

Cats: type B cats carry strong natural antibodies against type A blood, so vets test cats before even a first transfusion.

Of the eight main blood types, which is the rarest in the United States?

AB negative: yet anyone can receive AB plasma, whatever their own blood type.

In a blood-typing test, what visible reaction shows that a matching antigen is present?

Agglutination: antibodies in the test solution bind the matching antigen, making the cells stick together in clumps you can see.

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

Exposure to food, bacteria and viruses: in group O mothers some of these antibodies can cross the placenta and cause a usually mild disease in the newborn.

Which 2015 action film has its captured hero, a universal donor, forced to transfuse blood to a sick War Boy?

Mad Max: Fury Road has Max strapped to Nux's car as the pursuit begins, still hooked up as his donor. The film won six of its ten Academy Award nominations.

Genome sequencing in 2012 showed that which ancient human had type O blood, brown eyes and lactose intolerance?

Ötzi the Iceman died some 5,300 years ago, yet his DNA also showed a raised risk of heart disease and the earliest known human infection with the Lyme disease bacterium.

Blood group tests suggested that the mystery mummy in tomb KV55 was a close relative of which pharaoh buried nearby?

Tutankhamun and the KV55 body shared the same blood group, and the two mummies also looked strikingly alike. The tests pointed to a father and son, or a pair of brothers.

In which country did James Harrison give blood 1,173 times because it held a rare antibody that protects unborn babies?

Australia stopped him only at 81, the upper age limit for donors there. His antibodies went into every batch of the Rh disease treatment made in New South Wales.

Which biting insects prefer to feed on people with type O blood, plenty of skin bacteria and high body heat?

Mosquitoes that bite are always female. In some species they need a blood meal before they can produce eggs.

World Blood Donor Day falls on 14 June each year to mark which event in the life of Karl Landsteiner?

His birthday was 14 June 1868. The day was first held in 2004, backed by the World Health Organization, to thank the voluntary unpaid donors that a safe blood supply depends on.

DNA from two fossils found at El Sidrón in Spain showed that which extinct human relatives also had type O blood?

Neanderthals carried the same genetic change that gives modern people type O. It must therefore have arisen before the two lineages split, more than 500,000 years ago.

Which blood type, found in fewer than 4% of Americans, is known in transfusion medicine as the universal recipient?

AB positive patients carry the A, B and Rh antigens themselves, so their plasma holds no antibodies against donated cells. Their own red cells can go only to others of the same type.

In 1984 'Baby Fae' received the heart of which animal, a graft rejected largely because of a blood type mismatch?

A baboon heart kept Fae alive for 21 days. She was type O, but fewer than 1% of baboons are, and all seven of the available donors were type AB.

Which blood type is the most common in the United States, carried by roughly 38% of the population?

O positive blood is also the type hospitals transfuse most, since it suits any patient whose own type is Rh positive. That covers more than 80% of people.

Which newborn condition, eased by light therapy, turns dangerous when a mother's Rh antibodies attack her baby's blood?

Jaundice sets in when a yellow pigment from the destroyed cells builds up faster than the newborn's immature body can clear it. In severe Rh disease the pigment can settle in the brain.

Karl Landsteiner's 1901 discovery of the ABO blood groups earned him which honour nearly three decades later?

A Nobel Prize in Physiology or Medicine came in 1930. After his death he also received a Lasker Award and was hailed as the father of transfusion medicine.

Karl Landsteiner's 1901 paper described three blood groups; which fourth group did two of his students add a year later?

AB was found by Adriano Sturli and Alfred von Decastello, who at first gave it no name at all. AB plasma carries neither ABO antibody, so it can be given to patients of any group.

A person with type A blood naturally carries which antibody in their plasma, ready to attack mismatched donor cells?

Anti-B antibodies form in the first years of life with no transfusion needed, which is why even a first mismatched unit is dangerous. People with type B blood carry the mirror image.

When a hospital patient is given blood of the wrong ABO group, a potentially fatal event, what is typically to blame?

Human error is the usual cause, most often a clerical slip that sends a unit to the wrong patient. The patient's own antibodies then attack the transfused cells.

Which patients can receive a heart from a donor of an incompatible ABO group, a practice first tried in Toronto in 1996?

Young infants have immune systems too undeveloped to attack the mismatched organ. In the first study period, allowing such transplants cut deaths on the waiting list from 58% to 7%.

People with type O blood are the most susceptible to which disease, whose diarrhoea can dehydrate a victim within hours?

Cholera can drain the body so fast that some strains have killed within two hours of the first symptoms. Most patients, though, recover on simple oral rehydration therapy.

Blood typing was long used to confirm the identity and parentage of which animals, which have eight blood groups?

Horses, unlike humans, make no antibodies against foreign blood groups until they have met them, for instance through a transfusion or while giving birth.

In a 1991 episode of The Simpsons, which character has the rare blood type needed to save Mr. Burns's life?

Bart gives the blood, but Mr. Burns sends only a thank-you card with no reward, to Homer's rage. The writers took the idea from a co-worker who had needed a transfusion.

Researchers Watkins and Morgan showed that the A and B blood group antigens are each defined by which kind of molecule?

Sugars make all the difference: one called N-acetylgalactosamine marks type A, while plain galactose marks type B.

A child who inherits an A allele and a B allele has type AB blood, a textbook case of which genetic pattern?

Codominance means neither allele masks the other, so the child's cells display both antigens at once. It is why a type A parent and a type B parent can have an AB child.

Which term describes the bursting of blood cells that makes a transfusion of the wrong type so dangerous?

Hemolysis after a mismatched transfusion can bring on shock and organ failure. Runners can develop it in their feet, from the impact of each stride.

Which pre-transfusion test, pioneered by Reuben Ottenberg in 1907, mixes a patient's plasma with donor cells?

Cross-matching works as a dress rehearsal: if the patient's antibodies bind the donor's cells in the tube, the unit is rejected. Some hospitals now let a computer compare the records instead.

Non-secretors, whose body fluids carry no ABO antigens, are less prone to the commonest strains of which stomach bug?

Norovirus gets a grip on the gut by binding to blood group antigens secreted along its lining, so people who secrete none give it little to hold. About 20% of white people are non-secretors.

Which inherited blood disorder leaves many patients of African descent relying on matched African-American donors?

Sickle cell disease patients may need rare blood types, and some of those occur almost only within one ethnic group. More than 300 antigens beyond A, B and Rh go into such types.

Which organ do families trade in a 'paired exchange', used when a willing donor's blood type does not suit the patient?

A kidney can be spared by a living person, so two mismatched pairs can simply swap donors. One chain of such swaps, completed in 2014, involved 70 participants.

In 1963 William Liley gave the first successful blood transfusion to a baby still in the womb, working in which country?

New Zealand's Liley succeeded only after three failed attempts. The unborn patient had Rh disease and had been expected to die before birth.

ABO blood groups were shown in 1910 to be inherited according to the laws of which 19th-century scientist?

Gregor Mendel worked out his rules on pea plants, and human blood groups turned out to follow them too: a child's type reflects one inherited variant from each parent.

The gene that determines a person's ABO blood group, made up of seven exons, is located where in the human genome?

Chromosome 9 carries the ABO gene near the tip of its long arm. The Rh genes lie on a different chromosome, so a child's ABO group and Rh status are inherited separately.

The antibodies of the ABO system usually belong to which class, one that cannot cross the placenta to an unborn baby?

IgM antibodies stay on the mother's side of the placenta, which is why an ABO mismatch between mother and baby rarely causes serious illness. Rh antibodies are IgG, which does cross.

Which blood group antigen, found in 1953, is common among Indigenous peoples of the Americas yet rare in Europeans?

Diego takes its name from the Venezuelan family in which it was found. It also occurs in people of Chinese and Japanese ancestry, a sign that the two populations share ancient roots.

Which kind of donation, useful for people with rare blood types, stores a patient's own blood for planned surgery?

Autologous donation rules out a mismatch, since donor and recipient are the same person. Such blood is not always screened as strictly as the general supply.

In which part of a 1900 paper did Karl Landsteiner first report that one person's serum could clump another's blood?

A footnote of just two sentences held the first evidence that blood differs from person to person. Until then all human blood was assumed to be alike.

The P blood group antigen is the receptor that parvovirus B19 uses to enter cells, causing which childhood rash illness?

Fifth disease earns its nickname, slapped cheek syndrome, from the bright red rash it leaves on a child's face. About half of adults are immune thanks to an earlier infection.

Which German mathematician showed in 1924 that ABO blood groups are inherited through multiple alleles of a single gene?

Felix Bernstein settled the question with statistical analysis rather than laboratory work. He is better known for the Schröder–Bernstein theorem, a central result of set theory that he proved in 1896.

Blood cells from a type A donor carry only the A antigen, so they suit patients of which two ABO groups?

A and AB patients already carry the A antigen themselves, so neither makes antibodies against it. Patients of the other two groups would attack the donated cells.

Guidelines reserve scarce universal-donor blood for patients of that type, untestable emergencies and which other group?

Women who may be pregnant are protected because a mismatched transfusion could sensitise their immune system and put a baby they carry at risk of Rh disease.

The O version of the ABO gene makes no working enzyme because of which tiny change in its DNA sequence?

One deleted letter, a single guanine, throws the rest of the gene's code out of step. The result is a stunted protein only 117 amino acids long that does nothing.

Which famous British statistician devised the CDE notation for Rh blood types together with R. R. Race?

Ronald Fisher built the notation on a theory of three genes, which proved wrong, as did a rival theory of one; there are in fact two. His CDE letters are still in everyday use.

Type A and type B parents can have a type O child only when both are described by which genetic term?

Heterozygous parents each carry one working allele and one silent O allele. A child who inherits the silent copy from both makes neither the A nor the B antigen.