24/05/2026
Beyond ABO:
The Hidden Complexity of Blood
Most people know their blood type as A, B, AB, or O, along with positive or negative Rh status. But those familiar categories represent only a small part of human blood diversity.
Scientists have now identified 47 blood group systems containing more than 360 known blood antigens. These antigens are molecules found on the surface of red blood cells, and even tiny differences between donors and recipients can sometimes trigger severe immune reactions.
The newly recognized MAL blood group system centers on the AnWj antigen, a rare blood marker first identified in 1972. The name “AnWj” comes from the first patients found to produce the antibody, Anton and Wj.
Why This Discovery Matters:
The vast majority of people, more than 99.9%, are AnWj-positive. But for the tiny number who are AnWj-negative, receiving incompatible blood could trigger a serious transfusion reaction.
Until now, identifying these individuals has been extremely difficult because the genetic basis of the blood group was unknown.
The discovery means new genetic tests can now be developed to identify rare donors and patients before transfusions take place. Researchers say these tests could eventually be integrated into existing blood typing platforms.
This is especially important because many AnWj-negative cases are not inherited. Certain blood disorders and cancers can temporarily suppress the Mal protein, causing patients to appear AnWj-negative even though they do not carry the rare genetic form.
The inherited version itself appears to be extraordinarily uncommon. The study identified only five genetically AnWj-negative individuals, including members of an Arab-Israeli family. Researchers suspect there may be additional undiagnosed cases worldwide now that testing is possible.
Reference: “Deletions in the MAL gene result in loss of Mal protein, defining the rare inherited AnWj-negative blood group phenotype” by Louise A Tilley, Vanja Karamatic Crew, Tosti J Mankelow, Samah A AlSubhi, Benjamin Jones, Abigail Borowski, Vered Yahalom, Lilach Finkel, Belinda K Singleton, Piers J Walser, Ashley Mark Toye, Timothy J Satchwell, Nicole M Thornton, 18 August 2024, Blood.