A groundbreaking discovery in the realm of blood science has finally unraveled a mystery that lingered for over half a century. In 1972, a pregnant woman’s blood sample presented an intriguing anomaly: it lacked a specific surface molecule that was present on all other known red blood cells at that time. Fast forward to 2024, and researchers from the UK and Israel have made significant strides in understanding this peculiar absence, leading them to officially identify a new blood group system in humans.
This remarkable achievement, described in a recent publication, marks the end of a long journey for many dedicated scientists. Louise Tilley, a hematologist with the UK National Health Service, expressed her excitement, stating, "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." Tilley has devoted nearly two decades to researching this fascinating aspect of blood.
While most people are aware of the ABO blood group system and the Rh factor (the positive or negative classification), it’s important to note that humans actually possess a diverse range of blood group systems. These are determined by various proteins and sugars that adorn the surface of our blood cells.
But here's where it gets controversial... The significance of these antigen molecules extends beyond mere classification; they serve as crucial identification markers, helping our bodies discern between what is 'self' and what is potentially harmful 'not-self.' This distinction is vital, especially during blood transfusions, as mismatches can lead to severe reactions or, in the worst-case scenarios, even fatalities.
The early 20th century saw the identification of many major blood groups. However, discoveries made in more recent years, such as the Er system noted in 2022, often pertain to a limited number of individuals. The newly identified blood group continues this trend, as it is also quite rare. Tilley noted the challenges faced by researchers, pointing out that genetic cases like this one are exceptionally uncommon.
Research indicated that over 99.9% of individuals possess the AnWj antigen, which was notably absent in the blood of the 1972 patient. This antigen resides on a protein linked to myelin and lymphocytes, prompting the researchers to designate the new blood group system as the MAL blood group. When both copies of a person’s MAL gene are mutated, they exhibit an AnWj-negative blood type, similar to that of the woman from 1972. Interestingly, Tilley and her team also discovered three AnWj-negative patients who did not have this mutation, suggesting that certain blood disorders may inhibit the antigen's presence.
Tim Satchwell, a cell biologist from the University of the West of England, elaborated on the complexities of this research, stating, "MAL is a very small protein with some interesting properties which made it difficult to identify and meant we needed to pursue multiple lines of investigation to accumulate the proof we needed to establish this blood group system."
To definitively identify the responsible gene, the research team took a groundbreaking step by introducing the normal MAL gene into blood cells that were previously AnWj-negative. This process effectively restored the AnWj antigen to those blood cells. Notably, the MAL protein plays an essential role in maintaining the stability of cell membranes and facilitating cellular transport. Previous studies indicated that the AnWj antigen does not appear in newborns but manifests shortly after birth.
All AnWj-negative patients involved in the study shared the same mutation, yet no additional cell abnormalities or diseases were associated with it. With the genetic markers for the MAL mutation now established, patients can undergo testing to determine whether their negative MAL blood type is inherited or the result of suppression—this could indicate other underlying medical issues.
And this is the part most people miss... These rare blood types can have life-altering consequences for patients. Understanding them more thoroughly could lead to lifesaving interventions. The findings from this significant research were published in the journal Blood. An earlier version of this article first appeared in September 2024.
