Scientists solve a 50-year mystery and discover a new human blood group

Scientists solved the mystery of AnWj, a blood group antigen first recognized in 1972. They found that its presence depends on the MAL gene. This turns a long-standing medical puzzle into a defined blood group system called MAL. The discovery matters because rare blood differences can complicate transfusions.

Most people carry the AnWj antigen on their red blood cells. A very small number do not. If an AnWj-negative person makes antibodies against AnWj, those antibodies may react with transfused red cells carrying the antigen. Identifying the genetic cause connects the blood-cell feature to a specific biological mechanism.

The immediate benefit is better testing. Laboratories can look for the responsible gene when they encounter an unusual AnWj-negative result. Doctors can then identify rare compatible donors more efficiently and reduce the chance of a dangerous transfusion reaction. The discovery also formally adds MAL to recognized blood group systems.

A blood group system is a recognized collection of red-cell antigens linked by a biological basis. MAL is the newest system described in the article. Its defining feature is AnWj, the antigen whose genetic cause scientists have now identified. This gives AnWj a clear place in blood-group science.

The key link is the MAL gene. When the relevant MAL protein is present in red blood cells, the AnWj antigen can be expressed. People lacking the antigen are described as AnWj-negative. If their immune systems encounter AnWj through transfusion, they may produce antibodies that recognize it. Those antibodies can make incompatible blood unsafe.

This classification is more than a new name. It gives laboratories a genetic target for investigating unusual blood samples. It can also improve donor matching for the extremely rare AnWj-negative patients who need compatible blood. The article therefore connects a puzzling antigen with a practical testing and transfusion system.

The AnWj antigen was recognized in 1972, but identifying its genetic cause required much more than observing an unusual blood reaction. Scientists had to connect a rare red-cell pattern with a specific gene. That is difficult when very few people share the unusual pattern and suitable samples are scarce.

An AnWj-negative result also creates a demanding comparison. Researchers must distinguish a true inherited absence from changes caused by illness, treatment, or laboratory conditions. They then need genetic evidence showing that alterations in one gene explain the missing antigen. The article confirms the final result: the responsible gene is MAL.

This long timeline does not mean the antigen was unimportant. It shows how rare blood groups can remain genetically unexplained even when their transfusion relevance is known. Now that MAL has been identified, laboratories have a clearer route for confirming AnWj-negative cases. Future testing should become faster, more reliable, and easier to standardize.

AnWj-negative people are described in the article as extremely rare. That means most hospitals and blood banks will encounter them only occasionally, if at all. Their rarity makes ordinary blood-group screening less likely to flag them, because routine testing usually focuses on clinically common antigens and antibodies.

The problem becomes clearer during a complicated transfusion investigation. A patient may first appear to have an unexplained antibody or an unusual compatibility result. Specialists then need additional testing to determine whether AnWj is involved. Without a known genetic marker, confirming the result and locating another person with the same blood type can take considerable effort.

Identifying the MAL gene changes that situation. Genetic testing can help confirm an AnWj-negative result, even when standard blood tests are inconclusive. Blood services can record those findings and search more deliberately for rare compatible donors. The article’s main promise is practical: a hidden, exceptionally uncommon blood type should become easier to identify and manage.

Blood transfusions are safest when the recipient’s antibodies do not recognize antigens on donated red cells. An AnWj-negative patient may be at risk if they have developed antibodies against AnWj and receive blood carrying that antigen. The article warns that such incompatibility can cause potentially dangerous transfusion reactions.

In a reaction, antibodies attach to the donor’s red cells. This can activate immune destruction, known as hemolysis. Possible consequences include fever, pain, low blood pressure, anemia, or kidney injury. The exact severity depends on the antibody and clinical circumstances, so medical teams treat suspected reactions urgently. Not every AnWj-negative person will necessarily have anti-AnWj antibodies.

The discovery helps reduce this risk by making the underlying blood type easier to confirm. Once doctors know a patient is AnWj-negative, they can investigate relevant antibodies and seek appropriately matched blood. The result is more informed transfusion planning, especially for the tiny number of patients whose blood would otherwise be difficult to classify.

Knowing the MAL gene gives laboratories a precise way to investigate an AnWj-negative result. Instead of relying only on difficult antibody and antigen testing, they can examine whether the patient carries genetic changes linked to absent AnWj. This is especially valuable when the blood sample is unusual or testing results are hard to interpret.

For example, if a patient needs a transfusion and testing suggests AnWj is missing, a MAL-based test can help confirm the finding. The blood service can then search its records, rare-donor networks, or additional samples for donors with compatible characteristics. Clinicians can also avoid treating a potentially incompatible donor unit as routine blood.

The article presents this as a major practical benefit. Better identification should reduce delays and improve protection from transfusion reactions. It will not make compatible blood instantly available in every case, but it gives doctors reliable information for matching patients and donors. That is particularly important because AnWj-negative people are extremely rare.

Red blood cells carry surface markers called antigens. People also have antibodies in their plasma that recognize particular foreign markers. Before transfusion, doctors match important donor and recipient blood-group features, because the goal is to avoid an antigen meeting its corresponding antibody. The familiar ABO and Rh systems are major examples, but many other antigens matter.

For instance, a person lacking a specific antigen may become exposed to it through pregnancy or transfusion. Their immune system can then make antibodies against that antigen. If they later receive red cells carrying it, the antibodies may attach to the cells and cause hemolysis. In the AnWj case, an AnWj-negative patient with anti-AnWj could react to AnWj-positive blood.

Compatibility testing looks for these risks before blood is given. The MAL discovery adds a genetic tool for identifying the rare AnWj-negative state. That information can improve donor selection and help protect patients whose unusual antigen pattern might otherwise be missed.