In 1972, scientists first identified a pregnant woman lacking a specific molecule present in the blood of most individuals. Fifty years later, researchers from Israel and the UK unveiled the mystery in a study published in the journal Blood. Their findings revealed a previously unknown blood group, termed MAL.
According to Louise Tilley, a hematologist with the UK's National Health Service, this discovery marks a significant achievement and culmination of a long-term team effort aimed at improving care for rare but important patients.
The majority of people are familiar with the prominent ABO blood group system, defined by the presence of antigens A, B, and the Rh factor. However, there are many blood group systems based on various proteins and sugars on blood cell surfaces. These molecules, known as antigens, serve as identification markers for the body to distinguish its own cells from potentially harmful foreign cells.
Blood transfusions have been attempted since the 15th century, but the lack of knowledge regarding blood groups and their compatibility led to disastrous results. Austrian immunologist Karl Landsteiner first identified blood groups in 1901, earning a Nobel Prize in 1930 for his work, which established the foundation for modern transfusion medicine.
Currently, there are around 50 known blood groups, with the ABO system being the most recognized. In this system, blood types are categorized based on the presence of antigens:
Type A: Has antigen A and produces antibodies against antigen B.
Type B: Has antigen B and produces antibodies against antigen A.
Type AB: Contains both antigens and is a universal recipient.
Type O: Lacks antigens and produces antibodies against both antigens, making it a universal donor.
Compatibility is crucial; incompatible blood transfusions can trigger severe reactions, including hemolytic reactions and organ failure.
Prior research indicated that over 99.9% of people possess the AnWj antigen, which was absent in the 1972 case. The new blood group MAL was linked to a mutation affecting the MAL gene. Tilley and her team identified three patients with the rare blood group who did not carry this mutation, suggesting that blood disorders may also suppress the antigen.
Tim Satchwell, a cell biologist at the University of the West of England, explained that MAL is a small protein with unique properties that complicated its identification.
With the identification of genetic markers associated with the MAL mutation, testing for MAL status is now possible. Individuals can determine whether their negative MAL status is inherited or due to suppression, potentially indicating other underlying medical issues. This research paves the way for new genotypic tests to identify rare individuals and reduce transfusion-related complications.