There's a global shortage of blood supplies needed for life-saving transfusions due to factors that include an aging population with a higher demand for it and a lack of volunteer donors. However, even if there was an ample blood supply, it's not as simple as just giving blood when it's needed.

Each blood group (A, B, or AB) or type is identified by the presence of A and B antigens attached to sugar (oligosaccharide) chains on the surface of red blood cells. Blood cells in group O carry no antigens. When a blood transfusion is given, the donor and recipient's blood groups need to match. Otherwise, the immune system will attack and destroy the donated blood cells, causing a potentially fatal reaction.

Researchers at the Technical University of Denmark (DTU) and Lund University, Sweden, have used enzymes produced by a common gut bacteria to remove the A and B antigens from red blood cells, bringing them one step closer to creating universal donor blood.

"For the first time, the new enzyme cocktails not only remove the well-described A and B antigens, but also extended variants previously not recognized as problematic for transfusion safety," said Maher Abou Hachem, co-corresponding author of the study and scientist at DTU's Department of Biotechnology and Biomedicine.

As mentioned, the term 'blood group' denotes the combination of antigens present on the surface of a person's red blood cells. By 'extended variants,' Abou Hachem is referring to blood group antigens discovered since the canonical four were more than 120 years ago. The International Society of Blood Transfusion (ISBT), defines a blood group system as a genetically discrete system of one or more antigens. As of November 2023, there were 45 recognized blood group systems containing 362 red blood cell antigens that are genetically determined by 50 genes.