Scientists Finally Crack a 50-Year Mystery: The Discovery of the MAL Blood Group System

In a stunning breakthrough that bridges decades of medical detective work, researchers from the UK and Israel have officially described a new blood group system in humans—dubbed the MAL blood group—ending a scientific mystery that began with a single blood sample taken in 1972.

The story begins with a pregnant woman whose blood sample, collected over 50 years ago, was found to be missing a surface molecule present in all other known red blood cells at the time. For decades, this anomaly remained unexplained, baffling hematologists and immunologists alike. Now, thanks to cutting-edge genetic analysis and relentless scientific inquiry, the mystery has finally been solved.

A Discovery Decades in the Making

The newly identified MAL blood group is named after the myelin and lymphocyte protein (MAL) that carries the missing antigen, known as AnWj. According to the research team, more than 99.9% of people possess this antigen, making its absence extraordinarily rare. The discovery was published in the prestigious journal Blood in 2024, marking a major milestone in transfusion medicine.

“This represents a huge achievement, and the culmination of a long team effort, to finally establish this new blood group system and be able to offer the best care to rare, but important, patients,” said Louise Tilley, a hematologist from the UK National Health Service, who has dedicated nearly two decades to unraveling this blood quirk.

The Science Behind the Discovery

Blood types are determined by the presence or absence of specific antigens—molecules that act as biological “ID tags” on the surface of red blood cells. These antigens help the immune system distinguish between “self” and “non-self.” When a person receives a blood transfusion, their immune system can react violently if the donor’s blood contains unfamiliar antigens, sometimes with fatal consequences.

While most people are familiar with the ABO and Rh blood group systems, humans actually have many different blood group systems based on the wide variety of proteins and sugars that coat our blood cells. The MAL system is now the latest addition to this complex classification.

The research team found that when both copies of a person’s MAL gene are mutated, they end up with an AnWj-negative blood type—just like the 1972 patient. Interestingly, they also identified three AnWj-negative patients who did not have this mutation, suggesting that certain blood disorders can suppress the antigen.

The Challenges of Discovery

Identifying the MAL gene was no easy feat. “The work was difficult because the genetic cases are very rare,” explained Tilley. The MAL protein is a very small molecule with unique properties that made it challenging to study. Researchers had to pursue multiple investigative approaches to gather enough evidence to establish the new blood group system.

To confirm their findings, the team inserted the normal MAL gene into blood cells that were AnWj-negative. This effectively delivered the AnWj antigen to those cells, providing the final proof needed to validate the discovery.

Implications for Medicine and Patient Care

The MAL protein plays a vital role in maintaining cell membrane stability and aiding in cellular transport. Previous research has shown that the AnWj antigen is not present in newborns but appears soon after birth. All AnWj-negative patients in the study shared the same mutation, but no other cell abnormalities or diseases were linked to it.

With the genetic markers behind the MAL mutation now known, patients can be tested to determine if their negative MAL blood type is inherited or due to suppression—which could flag an underlying medical problem. This discovery has the potential to save lives, particularly for patients with rare blood types who require transfusions.

A Legacy of Scientific Persistence

The journey to discover the MAL blood group system is a testament to the power of scientific persistence. What began as a curious anomaly in a 1972 blood sample has now become a groundbreaking discovery that could transform transfusion medicine. As researchers continue to explore the complexities of the human blood system, this discovery serves as a reminder that even the smallest clues can lead to monumental breakthroughs.

Related: Scientists Identify New Blood Group, And It’s The World’s Rarest

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