In a groundbreaking proof-of-concept study, researchers successfully converted type A donor lungs into "universal" organs. These modified lungs could theoretically be transplanted into any recipient, regardless of blood type, as long as organ size matches.
Human blood types are defined by antigens on red blood cell surfaces, inherited from parents. These fall into 35 systems, with ABO (A, B, AB, O) and Rh being most critical for transplants.
Type A blood has A antigens, type B has B antigens, AB has both, and O has none. Plasma contains corresponding antibodies: type A has anti-B, type B has anti-A, AB has none, and O has both anti-A and anti-B.
A type A recipient transfused with type B blood triggers an immune rejection, as the body views it as foreign.
Type O recipients, with anti-A and anti-B antibodies, can only receive from O donors. Conversely, O organs—lacking A/B antigens—are universal donors. High demand for O organs means type O patients face longer waits; a study three years ago found they have a 20% higher risk of dying while awaiting lung transplants.
Leading the effort is Dr. Marcelo Cypel, Surgical Director at the Ajmera Transplant Centre and Professor of Surgery at the University of Toronto, collaborating with Stephen Withers from the University of British Columbia.
Withers' team previously developed a 2018 method using gut-derived enzymes to strip A, B, and AB antigens from red blood cells, converting them to universal type O.
In this study, they applied two enzymes—FpGalNAc deacetylase and FpGalactosaminidase—to type A donor lungs during ex vivo lung perfusion (EVLP), which sustains organs outside the body for hours.
After four hours, 97% of A antigens were removed—a duration compatible with clinical EVLP protocols of 4-5 hours.
In paired experiments, enzyme-treated right lungs from three type A donors were compared to untreated left lungs. Perfusion with type O plasma (containing anti-A/B antibodies) showed treated lungs functioning normally, while untreated ones exhibited hyperacute rejection.
This advance suggests "universal" organs viable for any compatible-sized recipient. The enzymes could extend to other organs and blood transfusions.
Next: human clinical trials to confirm enzyme safety and address potential antigen regrowth from new cells post-transplant, which could trigger rejection. These questions will be rigorously tested.
