The publicity materials here discuss an intriguing approach to reducing the issues of rejection associated with organ transplantation. Some of the underlying mechanisms relate to incompatible blood types. It is possible to perfuse an extracted organ with enzymes that convert the biochemistry associated with blood type to blood type O, which is compatible with other types. The result is an organ that can be transplanted with greater safety.
Blood type is determined by the presence of antigens on the surface of red blood cells - type A blood has the A antigen, type B has the B antigen, type AB blood has both antigens and type O has none. Antigens can trigger an immune response if they are foreign to our bodies. That is why for blood transfusions we can only receive blood from donors with the same blood type as ours, or universal type O. Likewise, antigens A and B are present on the surfaces of blood vessels in the body, including vessels in solid organs. If someone who is type O (meaning they have anti-A and anti-B antibodies in their bloodstream) received an organ from a type A donor, for example, the organ in all likelihood would be rejected. Consequently, donor organs are matched to potential recipients in the waitlist based on blood type, among other criteria.
This proof-of-concept study used the Ex Vivo Lung Perfusion (EVLP) system pioneered as a platform for the treatment. The EVLP system pumps nourishing fluids through organs, enabling them to be warmed to body temperature, so that they can be repaired and improved before transplantation. Human donor lungs not suitable for transplantation from type A donors were put in the EVLP circuit. One lung was treated with a group of enzymes to clear the antigens from the surface of the organ, while the other lung, from the same donor, remained untreated. The team then tested each of the lungs by adding type O blood (with high concentrations of anti-A antibodies) to the circuit, to simulate an ABO-incompatible transplant. The results demonstrated that the treated lungs were well tolerated while the untreated ones showed signs of rejection.