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Beyond A, B, and O: The Science of Discovering New Blood Groups

Tue, 24 Jun 2025 11:20:42 GMT
Beyond A, B, and O: The Science of Discovering New Blood Groups

When you think of blood types, the familiar A, B, AB, and O groups likely come to mind, along with the positive or negative Rh factor. But what if this was just the tip of the iceberg? The world of hematology is buzzing with the discovery of new blood group systems, revealing a far more complex and fascinating landscape of human biology than previously understood. These discoveries are not just academic curiosities; they have profound implications for transfusion medicine and pregnancy, potentially saving lives.

Unlocking a 50-Year-Old Mystery: The MAL Blood Group

Imagine a medical puzzle that took half a century to solve. In 1972, a blood sample from a pregnant woman revealed a mysterious anomaly: her red blood cells were missing an antigen, a surface molecule, that was present in over 99.9% of the population. This antigen was named AnWj. For decades, the genetic basis for this rare blood type remained unknown.

Fast forward to recent years, and a team of researchers from the UK and Israel finally cracked the case. Through international collaboration and advanced genetic sequencing, they discovered that individuals lacking the AnWj antigen have deletions in both copies of a gene called MAL. This gene is responsible for producing the MAL protein, which plays a role in stabilizing cell membranes. This breakthrough led to the official recognition of the 47th blood group system, named MAL, by the International Society of Blood Transfusion (ISBT) in 2024.

This discovery is crucial for a few reasons. People who are AnWj-negative can develop antibodies if they receive AnWj-positive blood, leading to a potentially life-threatening transfusion reaction. Now, with the ability to perform genetic testing, doctors can identify these rare individuals and ensure they receive compatible blood. The absence of the AnWj antigen can be inherited or can be a temporary result of certain illnesses like cancer or blood disorders. The new genetic tests can help distinguish between these two scenarios, potentially flagging an underlying medical condition.

A World of Rarity: The "Gwada Negative" Blood Type

In another remarkable discovery, French scientists identified what is currently believed to be the world's rarest blood type in a woman from the Caribbean island of Guadeloupe. This new blood type, dubbed "Gwada negative," was found in a single individual who is, for now, the only known person in the world with this specific genetic makeup.

The journey to this discovery began in 2011 when a "very unusual" antibody was detected in the patient's blood during routine pre-surgery tests. However, it wasn't until 2019, with the advent of high-throughput DNA sequencing, that scientists could finally identify the genetic mutation responsible. In June 2025, the ISBT officially recognized this as the 48th blood group system.

This woman is considered her own universal donor, as she can only safely receive blood from herself. The discovery of "Gwada negative" highlights the incredible diversity of human genetics and underscores the importance of ongoing research into rare blood types. Finding more individuals with this blood group is now a priority for researchers, as it will allow for better care for these unique patients.

The Expanding Universe of Blood Groups

Beyond MAL and "Gwada negative," scientists are continuously expanding the map of human blood groups. The International Society of Blood Transfusion (ISBT) now recognizes 48 blood group systems, containing over 360 recognized blood antigens.

Here are a few other notable examples:

  • Er Blood Group System: Recognized as the 44th blood group system, the Er system involves five antigens carried on the Piezo1 protein. First described 40 years ago, its genetic basis was only recently uncovered. Certain rare variations within this system, like Er4 and Er5, have been linked to severe hemolytic disease of the fetus and newborn (HDFN), a condition where the mother's immune system attacks the baby's red blood cells.
  • P1PK and GLOB Systems: These systems involve antigens that can act as receptors for various pathogens, including bacteria that cause urinary tract infections and meningitis, as well as Shiga toxin. Rare phenotypes within this group, like p, P1k, and P2k, can lead to the production of antibodies that may cause transfusion reactions and have been associated with a higher frequency of miscarriages. Recently, a new and extremely rare P blood group gene mutation was discovered in China, with a frequency of less than one in a million.
  • KANNO, SID, CTL2, PEL, MAM, EMM, and ABCC1: In recent years, the ISBT has ratified several new blood group systems, further highlighting the complexity of red blood cell biology.

The Science Behind the Discoveries

The accelerated pace of discovery is largely thanks to revolutionary advancements in genomics. Here's how scientists are uncovering these new blood groups:

  • DNA Sequencing: High-throughput DNA sequencing and whole-exome sequencing allow researchers to quickly and efficiently analyze a person's entire genetic code, pinpointing the specific gene mutations responsible for creating new or rare blood antigens.
  • Gene Editing: Technologies like CRISPR/Cas9 allow scientists to confirm the function of a gene. For example, by inserting a normal gene into cells that lack a particular antigen, they can see if the antigen appears, proving the gene's role.
  • Genotyping: DNA-based genotyping is becoming a powerful alternative to traditional antibody-based blood typing. It can identify antigens for which no testing reagents exist, a major advance for finding compatible blood for patients with rare antibodies. The National Center for Blood Group Genomics is a research hub that specializes in using this technology to improve transfusion safety.

Why Does This Matter for You?

While you may never encounter someone with a blood type like "Gwada negative," the ongoing discovery of new blood groups has far-reaching implications:

  • Safer Transfusions: For individuals with rare blood types, finding a compatible donor can be a matter of life and death. Identifying these rare groups and the genes that cause them allows blood banks to build registries of rare donors, ensuring that life-saving blood is available when needed.
  • Improved Pregnancy Outcomes: As seen with the Er blood group, some rare antigens can cause severe complications in pregnancy. Understanding these connections allows for better prenatal screening and management, protecting the health of both mother and child.
  • Personalized Medicine: In the future, your complete blood group profile could be a part of your electronic health record. This information could be used to select the best possible matched blood for transfusions, reducing the risk of complications, especially for patients who require chronic transfusions.
  • Understanding Disease: The study of blood group antigens can also provide insights into various diseases. For example, certain antigens in the P1PK system are known to be receptors for pathogens, influencing susceptibility to infections.

The science of blood groups is a dynamic and evolving field. With each new discovery, we gain a deeper appreciation for the intricate tapestry of human genetics and move one step closer to a future of truly personalized and safer medical care.

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