The "universal" transplant, without rejection, takes a huge leap forward

The “universal” transplant, without rejection, takes a huge leap forward

This work could be a game-changer for thousands of patients who are still waiting for a transplant due to the lack of a compatible donor.

In work spotted by Futura, Canadian researchers succeeded in altering the blood type of a graft in order to transplant it to a recipient who would otherwise have been incompatible. A resounding success that could eventually break the lock of donor-recipient compatibility entirely, which would be a real revolution in clinical medicine, but also in public health and even with social implications.

Today, the transplant process is both cumbersome and very stressful for those involved. The main reason: it is not only difficult to find donors, in particular for vital organs, but they must also be physiologically compatible; it is for this reason that we often turn to a family member when the emergency becomes critical.

Build artificial compatibility

This compatibility is determined by analyzing different physiological parameters starting with the blood group. On the scale of red blood cells, we notice that their membranes are dotted with small distinctive elements that vary according to blood group. This is an important marker because it tells the immune system that the red blood cells are part of what is called the “self” in immunology.

This term refers to all things that are intrinsically part of the body, as opposed to “non-self” which comes from an external source and usually provokes an immune response. This makes a crucial difference in how these elements are processed by the immune system.

The non-self elements will be hunted down by a veritable militia composed of the different types of immunity actors. To differentiate the self from the non-self, those involved in immunity will be interested in distinctive markers present on the surface of the object, such as are found on the surface of red blood cells. And it is precisely this that generates the first layer of incompatibility between two people; if the blood coming from another individual is from a group incompatible with that of the recipient, the surface antigens of the transfused blood will be assimilated to non-self and therefore expelled by the actors of immunity.

The only exception is type O, which is often referred to as “guniversal donor group” because it has both type A and B antigens. Type O blood or organs can therefore be transferred safely to another patient, regardless of their blood type. On the other side of the spectrum, it is the AB group that stands out for its status as the universal receiver.

The transplant, a delicate and exclusive process

The concept is substantially the same in the context of a transplant, since the blood vessels also present these same antigens. And in this case, the prolonged presence of an element assimilated to “non-self” in the organism can be very serious; if the graft is incompatible with the recipient, it can cause a rejection syndrome with potentially disastrous consequences. There is therefore an obvious interest in developing techniques to circumvent this fundamental obstacle.

And that is precisely what American researchers have managed to do. They started with two lungs from a type A donor on which they practiced a technique called Ex Vivo Lung Perfusion (EVLP). This keeps the organ alive outside the body during the conversion operation. For this, the system pumps nutritious fluids at body temperature through the circulatory system of the organ.

One of these two lungs was kept as is until the transplant to serve as a control. The other, on the other hand, underwent a washing with a fluid charged with a little particular enzymes, identified by English researchers whose objective was to achieve the production of universal blood. They then tested the compatibility of the two organs by subjecting them to a flow of type O blood.

Only a first step, but huge promises

And the result turned out to be quite striking. Indeed, the treated lung was exceptionally well tolerated for an organ from a theoretically incompatible donor. In contrast, the untreated lung quickly showed signs of rejection. This very clearly suggests that the treatment was effective. The researchers thus laid the foundations of a system making it possible to create universally transplantable lungs.

You don’t need to be a public health expert to understand the potential implications of this system: it could quite simply change the lives of thousands of patients awaiting transplants. This is all the more true for type O patients who, if they are universal donors, can only receive material from their own type. This makes the process even longer and more painful knowing that it is a rare blood group.

This is just an initial proof of concept. As it stands, it will still take a lot of work before obtaining a reliable and universal system; it is therefore not tomorrow that we will be able to make any organ compatible with any donor. But it is in this direction that research is headed. In all likelihood, we are therefore heading towards a small revolution that could change the situation before the democratization of organ cultivation.

The research paper is available here.

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