A 50-year-old mystery involving a missing molecular marker from a pregnant woman’s blood sample has led to the identification of a new blood group system. Researchers from the National Health Service (NHS) Blood and Transplant in the UK and institutions in Israel have described the MAL blood group system, a significant breakthrough in hematology.
Uncovering the Mal Blood Group
In 1972, medical professionals identified a striking anomaly when a pregnant woman’s blood lacked the AnWj antigen, a marker found on the red blood cells of over 99.9% of people. This discovery prompted years of study and culminated in the formal recognition of the MAL blood group system in 2023.
The team, led by Dr. Louise Tilley of the NHS and Dr. Tim Satchwell from the University of the West of England, detailed their findings in a research paper published in September. Dr. Tilley noted, “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.”
Blood Group Systems and Human Health
Blood groups are determined by specific proteins and sugars coating red blood cells, with the ABO system and Rh factor being the most widely recognized. These markers help the body identify its cells and distinguish them from potential threats. Mismatches in these markers during blood transfusions can trigger severe immune responses, even death.
While the MAL blood group is rare, its identification highlights the diversity of blood group systems and their medical significance. Most blood groups were discovered in the early 20th century, but rare systems like Er (described in 2022) and MAL emphasize the ongoing nature of hematological research.
Challenges in Identifying the Mal Blood Group
The MAL protein, which anchors the AnWj antigen, plays a key role in maintaining cell membrane stability and facilitating transport. However, its small size and rarity made it difficult to study. Researchers faced additional challenges due to the limited number of cases available.
Key findings from the study include:
- Inheritance vs. Suppression: Most AnWj-negative cases result from mutations in both copies of the MAL gene, but the researchers identified some cases where blood disorders suppressed the antigen instead.
- Protein Function: The AnWj antigen does not appear in newborns but develops shortly after birth, hinting at its role in cellular development and stability.
To confirm their hypothesis, the team inserted a functioning MAL gene into AnWj-negative blood cells, restoring the missing antigen.
Implications for Patient Care
The discovery of the MAL blood group system allows for more precise blood typing and diagnostics. Doctors can now test for the genetic markers behind the MAL mutation to determine whether a patient’s AnWj-negative status is inherited or linked to another condition.
The research also revealed that no diseases or abnormalities were associated with the AnWj-negative status in their subjects, emphasizing the blood group’s rarity and complexity. As more information comes to light, the study of blood groups like MAL could provide further breakthroughs in personalized medicine.
This research was published in Blood.