The discovery of a new blood group, MAL, has solved a 50- year-old mystery.
Researchers from NHS Blood and Transplant, and the University of Bristol, have identified the genetic background of the previously known but mysterious AnWj blood group antigen (Tilley, 2024). The AnWj antigen – a surface marker molecule) – was discovered in 1972 but its genetic background was unknown until now.
The findings allow identification and treatment of rare patients lacking this blood group.
The two best known blood group systems are ABO and Rh but blood is more complex and matching across the other groups can be lifesaving.
If people who are AnWj-negative receive AnWj-positive blood they may have a transfusion reaction, and this research allows development of new tests for detecting such rare individuals; hence reducing the risk of transfusion-associated complications.
The research team established that AnWj is carried on the Mal protein. More than 99.9% of people are AnWj-positive, and such individuals were shown to express full-length Mal protein on their red cells, which was not present on the cells of AnWj-negative individuals.
The most common reason for being AnWj-negative is due to suffering from a haematological disorder or some types of cancer which suppress antigen expression. A very small number of people are AnWj-negative due to a genetic cause.
For example, there were five genetically AnWj negative individuals in the study including a family of Arab-Israelis. The blood tested included a sample given by a lady in 2015 who was the first AnWj negative person to be discovered in the 1970s.
Louise Tilley (above), Senior Research Scientist, at NHS Blood and Transplant, and lead author of the paper said:
“The genetic background of AnWj has been a mystery for more than 50 years, and one which I personally have been trying to resolve for almost 20 years of my career. It 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.”
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