After more than half a century of searching, scientists have identified the genetic source of the mysterious AnWj blood group antigen, establishing a brand-new blood group system called MAL. The breakthrough was led by researchers at NHS Blood and Transplant in Bristol, together with colleagues at the University of Bristol and the International Blood Group Reference Laboratory (IBGRL).
The AnWj antigen was first spotted on human red blood cells in 1972, but for decades no one knew which gene produced it or which protein carried it. The key turned out to be exome sequencing — the gene responsible wasn’t an obvious candidate, and very little was known about the Mal protein in red cells. In September 2026, the International Society of Blood Transfusion officially recognised MAL as the 49th blood group system.
The discovery has immediate clinical value. Patients who are AnWj-negative are extremely rare, and finding compatible donors has been extraordinarily difficult. Now that the genetic basis is understood, identifying these patients and matching donors becomes far easier, reducing the risk of dangerous transfusion reactions. The work also revealed that AnWj negativity can be either inherited — through a deletion of the MAL gene — or acquired, when certain disorders suppress Mal expression on red cells.
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