Scientists Solve a 50-Year Mystery of Human Blood Groups

Topic: Biology

Researchers at NHS Blood and Transplant in Bristol discovered that a mysterious marker on human red blood cells is caused by a genetic mutation. They identified the MAL gene as responsible for the AnWj antigen, which affects less than 0.1% of people.

For over 50 years, scientists were puzzled by a mysterious marker on human red blood cells called the AnWj antigen. But in 2026, researchers at NHS Blood and Transplant in Bristol finally solved the mystery.

The team found that the AnWj antigen is caused by a genetic mutation in the MAL gene. This gene produces a small protein called Mal, which is essential for the expression of the AnWj antigen on red blood cells. The researchers used a technique called whole exome sequencing to identify the genetic link between the MAL gene and the AnWj antigen.

The team discovered that people with the inherited form of the AnWj negative phenotype have homozygous deletions in both copies of the MAL gene. This means that they are missing the Mal protein on their red blood cells, which makes them more susceptible to transfusion reactions if they receive AnWj positive blood.

The researchers also demonstrated that introducing the normal MAL gene into laboratory cells made them reactive with AnWj antibodies, while introducing the altered form did not produce the same response. This confirmed that Mal is both necessary and sufficient for expression of the AnWj antigen.

Why It Matters

This discovery can help prevent dangerous transfusion reactions in patients who are AnWj negative. It also highlights the importance of understanding human blood groups, which can be critical in medical emergencies.

Key Facts

• The AnWj antigen was discovered in 1972 but its genetic source remained a mystery for over 50 years.
• Researchers at NHS Blood and Transplant in Bristol identified the MAL gene as responsible for the AnWj antigen.
• The MAL gene produces a small protein called Mal, which is essential for expression of the AnWj antigen on red blood cells.
• People with the inherited form of the AnWj negative phenotype have homozygous deletions in both copies of the MAL gene.
• This discovery can help prevent dangerous transfusion reactions in patients who are AnWj negative.

Key Terms

AnWj antigen

A marker on human red blood cells that affects less than 0.1% of people.

MAL gene

A gene that produces a small protein called Mal, which is essential for expression of the AnWj antigen on red blood cells.

Whole exome sequencing

A technique used to identify genetic links between specific genes and diseases or conditions.

Implications

This discovery can help prevent dangerous transfusion reactions in patients who are AnWj negative. It also highlights the importance of understanding human blood groups, which can be critical in medical emergencies.