Researchers from Great Britain’s National Health Service (NHS Blood and Transplant/ NHSBT) have discovered a new blood grouping system – solving a 50-year-old mystery.

The research team discovered a blood type called MALidentifying the genetic background of a rare blood antigen called AnWjwhich was discovered in 1972.

The NHSBT’s International Blood Group Reference Laboratory has developed a blood test that detects them patients who lack this rare antigen.

The discovery by NHSBT researchers marks the identification of the 47th blood group system and will save thousands of lives worldwide, according to NHSBT haematologist and senior researcher Louise Tilley.

“This is a huge achievement and the culmination of a long team effort to finally be able to identify this new blood grouping system and be able to provide the best possible care for these patients,” said Tilley.

Red blood cells, which circulate in our blood, have on their surface some substances called antigens. These antigens are unique to each person and define their blood type. Most of the major blood groups were recognized in the early 20th century. Most people are familiar with the two main blood group systems: the AB system and the Rhesus system.

According to the AB system, there are four main blood types A, B, AB and O. Each of these blood types can be ‘Rhesus positive’ or ‘Rhesus negative’. However, there are many more blood group systems than these two. In 2022, researchers from the University of Bristol completed the 44th blood group system called Er.

A 50-year-old mystery has been solved

It all started in 1972 when doctors discovered that a pregnant woman was missing a common antigen in her blood. After 50 years, NHSBT researchers to identify a new blood group system. Previous research found that over 99.9% of people have the AnWj antigen that was missing from the pregnant woman’s blood. This antigen is found in a protein of myelin and lymphocytes, which led the researchers to name the new system MAL blood type.

When a person has a mutated version of both copies of the MAL genes, their blood type is AnWj-negative, as in the case of a pregnant woman. The researchers identified three patients with this rare blood type who did not have this mutation, suggesting that blood disorders can sometimes cause suppression of the antigen.

“MAL is a very small protein with some interesting properties, which made it difficult to identify and so we had to follow multiple lines of inquiry to gather the evidence we needed to describe this blood group system,” said cell biologist Tim Satchwell from the University of the West of England .

To prove they had the right gene, after decades of research, the team introduced the normal MAL gene into blood cells that were AnWj-negative. In this way the AnWj antigen was effectively delivered to these cells.

The MAL protein is known to play a vital role in maintaining the stability of cell membranes and aiding cell transport. Previous research has found that AnWj appears soon after birth.

According to the researchers, all AnWj-negative patients included in the study had the same mutation. However, no other cellular abnormalities or diseases have been found to be associated with this mutation.

Now, scientists can develop tests to help identify AnWj-negative people to ensure the safety of transfusions and transplants. Patients can be tested to see if the negative MAL blood type is inherited or due to suppression, which could be an indication of another underlying medical problem.

These rare blood quirks can have devastating effects on patients, so the more of them we can understand, the more lives can be saved.

The research was published in the scientific journal “Blood”.