In a remarkable journey spanning over five decades, researchers have finally identified a new blood group system known as MAL, solving a mystery that began with a pregnant woman’s blood sample in 1972. This groundbreaking discovery, published in September 2024, marks a significant advancement in our understanding of human blood types and has the potential to improve care for patients with rare blood conditions.
The Origins of the Discovery
The story begins in 1972 when doctors noticed that a pregnant woman’s blood was missing a specific surface molecule found on all other known red blood cells. This peculiar absence led to the identification of the AnWj antigen, but it remained largely unexplored until recent advancements in genetic research allowed scientists to delve deeper into its origins. The research team, comprising experts from the UK and Israel, dedicated nearly 20 years to unraveling this enigma, culminating in the establishment of the MAL blood group system.
According to Louise Tilley, a hematologist with the UK National Health Service (NHS), “It represents a huge achievement… to finally establish this new blood group system and be able to offer the best care to rare, but important, patients.”
Understanding Blood Group Systems
While many people are familiar with the ABO blood group system and the Rh factor (the positive or negative designation), humans actually have numerous blood group systems based on various cell-surface proteins and sugars. These antigens serve as identification markers for our immune system, helping distinguish between ‘self’ and ‘non-self’ entities. When mismatched during transfusions, these antigens can trigger severe reactions or even prove fatal.
Most major blood groups were identified early in the 20th century. However, many newer groups, such as the recently identified Er blood group system, affect only a small number of individuals. The MAL blood group is similarly rare; previous studies indicated that over 99.9% of people possess the AnWj antigen that was absent in the original patient.
The Genetic Breakthrough
The research team discovered that when individuals have mutations in both copies of their MAL genes, they exhibit an AnWj-negative blood type. Interestingly, they also identified three patients who lacked this mutation but still presented with AnWj-negative blood types, suggesting that other factors might suppress this antigen.
To confirm their findings, researchers conducted experiments where they inserted a normal MAL gene into AnWj-negative blood cells. This successfully restored the AnWj antigen on those cells, providing crucial evidence for establishing the new blood group system.
Blood Transfusion Compatibility
Understanding how different blood groups interact during transfusions is critical for patient safety. Below is an overview of compatibility for major blood groups, including MAL:
| Blood Group | Can Receive From | Can Donate To |
|---|---|---|
| A+ | A+, A-, O+, O- | A+, AB+ |
| A- | A-, O- | A+, A-, AB+, AB- |
| B+ | B+, B-, O+, O- | B+, AB+ |
| B- | B-, O- | B+, B-, AB+, AB- |
| AB+ | All groups | AB+ |
| AB- | AB-, A-, B-, O- | AB+, AB- |
| O+ | O+, O- | O+, A+, B+, AB+ |
| O- | O- | All groups (universal donor) |
| MAL (AnWj-) | MAL (AnWj+) or compatible types | MAL (AnWj+) or universal types |
For individuals with the newly identified MAL blood group (AnWj-negative), it is crucial that they receive transfusions from donors who are either AnWj-positive or compatible types to avoid adverse reactions. Given that this antigen is rare—found in less than 0.1% of the population—finding compatible donors can be challenging.
Implications for Patient Care
The identification of the MAL blood group has significant implications for patient care, particularly for those requiring transfusions or pregnant women at risk of hemolytic disease. With this new understanding, healthcare providers can now develop tests to determine whether a patient’s AnWj-negative status is inherited or due to suppression caused by an underlying condition.
As Nicole Thornton from NHS Blood and Transplant pointed out, “The more we know about such rare blood group variations…the better care we are able to offer such patients in the future.”
Conclusion
The discovery of the MAL blood group system not only resolves a long-standing mystery but also enhances our ability to provide safe and effective medical care for individuals with rare blood types. As researchers continue to explore the complexities of human blood groups, every new finding brings us closer to understanding how these variations can impact health outcomes and patient safety.
Read More
[1] https://www.lifeblood.com.au/health-professionals/products/component-compatibility
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC4260296/
[3] https://www.spandidos-publications.com/10.3892/wasj.2023.211
[4] https://www.21stcentech.com/blood-transfusion-compatibility-research-leads-discovery-protein-markers/
[5] https://www.rch.org.au/bloodtrans/about_blood_products/blood_groups_and_compatibilities/