For anyone waiting for a kidney transplant, blood type can become an invisible barrier.
A donor kidney may be healthy. A recipient may desperately need it. Yet if their blood groups are incompatible, the immune system can recognize the transplanted organ as foreign and attack it almost immediately.
Now researchers have demonstrated something that once sounded far more futuristic: they temporarily altered the blood-group identity of a human kidney before transplantation, effectively converting it toward type O and allowing it to function inside a blood-type-incompatible human recipient without immediate hyperacute rejection.
It is not yet a treatment available to patients. It does not eliminate all transplant-rejection problems. But it may represent an important step toward a future in which donated kidneys could be matched more flexibly, potentially reducing one of the major obstacles in organ transplantation.
Why Blood Type Matters So Much in Kidney Transplants
Most people think of blood groups mainly in relation to blood transfusions, but the ABO system also matters when organs are transplanted.
Blood-group antigens are carbohydrate structures found not only on red blood cells but also on cells lining blood vessels inside organs.
A person with type A blood carries A antigens. Type B carries B antigens. Type AB has both, while type O lacks A and B antigens.
The immune system naturally carries antibodies against blood-group antigens it recognizes as foreign. That means placing a type A kidney into a person with type O blood can provoke a powerful antibody response against the kidney’s blood vessels.
In severe cases, this can produce hyperacute rejection, damaging an incompatible organ within minutes or hours.
Doctors can sometimes perform ABO-incompatible kidney transplantation using treatments that remove or suppress the recipient’s antibodies. These protocols can involve plasmapheresis and intensive immunosuppressive treatment, but they add complexity, cost and risks such as infection and bleeding.
Researchers therefore began exploring a very different strategy:
Instead of changing the recipient’s immune system, could they temporarily change the donated organ?
The Idea: Remove the Kidney’s Blood-Type Marker
Scientists discovered highly selective enzymes capable of cutting away the carbohydrate structures responsible for certain blood-group antigens.
Think of these enzymes as microscopic biochemical scissors.
For a type A organ, two enzymes can sequentially modify and remove the molecule that creates the A-antigen signature. The underlying structure resembles the antigenic surface associated with type O. Earlier laboratory work showed that these enzymes could substantially remove A antigens from human kidneys during machine perfusion.
Machine perfusion is particularly useful because a donated organ can be circulated with preservation fluid outside the body before transplantation.
That creates an unusual therapeutic opportunity: scientists can treat the organ directly without exposing the recipient’s entire body to the same intervention.
Researchers had previously demonstrated antigen conversion in isolated organs. The crucial unanswered question was whether an enzyme-treated kidney could survive contact with an incompatible human immune system.
That question has now been tested.
What Happened in the Human Experiment?
In the study published in Nature Biomedical Engineering, researchers treated a type A human kidney with antigen-removing enzymes while the organ was being preserved at low temperature.
The treatment removed most of the detectable A antigens from the kidney’s vascular surface.
The organ was then transplanted into a brain-dead recipient with type O blood who had antibodies capable of reacting against type A tissue. The experiment was conducted with family consent and ethical oversight.
The result was significant.
The transplanted kidney did not undergo immediate hyperacute rejection.
For approximately the first two days, researchers found no evidence of antibody-mediated rejection, demonstrating that the enzyme treatment had temporarily protected the incompatible kidney from the type of rapid immune destruction normally expected in such a mismatch.
That is the key achievement.
It does not mean researchers have created a permanently universal kidney. Rather, they demonstrated that the blood-group barrier can potentially be modified directly at the organ level.
Then Something Important Happened: The Antigens Returned
The kidney’s cells were still genetically type A.
Removing the surface antigens did not change the DNA instructions responsible for producing them.
As the kidney continued functioning, A antigens gradually began appearing again. Around the third day, the researchers observed antigen regeneration along with signs of immune-mediated injury.
This is currently one of the largest challenges facing the technology.
Scientists now need to determine whether antigen regeneration can be controlled long enough for the recipient’s immune system to adapt.
Possibilities being explored include repeated enzyme treatment, longer-lasting enzyme formulations or other strategies that suppress antigen reappearance during the critical early period following transplantation.
Interestingly, genetic analysis in the study also detected activity associated with accommodation—a phenomenon in which a transplanted organ gradually becomes more resistant to antibodies that would normally damage it.
That finding is preliminary, but it raises an intriguing possibility: perhaps an organ does not have to remain antigen-free forever. It may only need protection long enough for a more tolerant relationship between organ and immune system to develop.
This Research Is Bigger Than One Kidney
The kidney experiment is part of a broader field sometimes described as organ engineering.
Scientists are increasingly exploring ways to modify donor organs before transplantation rather than treating only the recipient afterward.
A separate 2025 study, for example, used another enzyme to remove more than 95% of blood-group B antigens from a donated kidney. That converted kidney was subsequently transplanted into a type O brain-dead recipient and avoided hyperacute rejection during the approximately 63-hour experiment.
Researchers have also previously explored enzyme-based blood-group conversion in lungs and other tissues.
Together, these studies suggest that ABO antigens may eventually become a modifiable characteristic rather than an absolute barrier.
Could We Really Have Universal Donor Kidneys?
Potentially—but the word universal needs to be interpreted carefully.
Blood type is only one component of transplant compatibility.
Even if scientists eventually make ABO incompatibility easier to overcome, physicians still need to consider HLA matching, pre-existing antibodies, immune suppression, organ quality, infection risk and many other clinical variables.
A converted type O kidney would therefore not mean that every kidney could automatically be transplanted into every person.
What it could mean is that one important compatibility restriction becomes far less limiting.
That alone could have enormous consequences.
Rather than matching an organ largely according to blood group, transplant teams could potentially have more flexibility to prioritize medical urgency, geographic considerations, organ quality and waiting time.
For patients who currently face particularly difficult blood-group matching, that could translate into more opportunities to receive a transplant.
Why Type O Patients Could Especially Benefit
Type O presents a frustrating transplant paradox.
People with type O blood generally need type O donor kidneys because their immune systems contain antibodies against both A and B antigens.
But type O organs can often be used for recipients with other compatible blood groups.
This creates intense demand for type O kidneys.
Researchers hope that converting A or B donor kidneys toward an O-like antigen profile could eventually expand the pool of organs available to these patients. UBC researchers have specifically highlighted the possibility of reducing the longer waits experienced by type O transplant candidates.
That is one reason this technology has generated so much interest.
What This Discovery Does Not Mean
Headlines about “blood-type-free” or “universal” kidneys can easily make the research sound further along than it actually is.
Several limitations matter.
First, the published type A experiment involved one organ transplanted into one brain-dead research recipient.
Second, the study lasted only several days.
Third, A antigens began returning, and evidence of antibody-mediated injury eventually developed.
Fourth, transplantation itself remains dependent on conventional immunosuppression and numerous other compatibility factors.
The researchers themselves describe this work as an important proof-of-concept rather than a finished clinical therapy. Further research, regulatory review and clinical trials will be necessary before enzyme-converted kidneys could become part of routine transplantation.
So this is not yet a procedure someone can request at a transplant center.
It is a glimpse of where transplantation may be heading.
The Bigger Lesson: Medicine Is Learning to Modify the Organ
For decades, transplantation has largely revolved around finding the best possible match and then suppressing the recipient’s immune response strongly enough to protect the donor organ.
This research flips part of that strategy.
Instead of asking only:
“How do we make the patient tolerate this organ?”
Scientists are increasingly asking:
“Can we prepare the organ so the patient is less likely to attack it?”
That shift opens fascinating possibilities.
Machine perfusion already allows clinicians to preserve and assess organs outside the body. In the future, that same window could potentially be used to repair, recondition or biologically modify donated organs before implantation.
Blood-group conversion may be only one example.
Protecting the Kidneys You Already Have Still Matters
Breakthrough transplantation science is remarkable, but most kidney disease develops quietly over many years.
Supporting kidney health often comes back to less dramatic habits.
Maintaining healthy blood pressure and blood sugar, staying appropriately hydrated, avoiding unnecessary chronic use of kidney-stressing medications, eating a balanced diet, exercising regularly and getting kidney function checked when medically appropriate remain fundamental.
Kidneys perform an extraordinary amount of work without attracting much attention—until their function starts declining.
That makes prevention and early detection especially valuable.
A Small Experiment With Potentially Enormous Implications
A kidney did not permanently lose its biological blood type.
Researchers did not eliminate transplant rejection.
And universal kidneys are not ready for hospitals tomorrow.
But something important did happen: scientists demonstrated inside a human body that blood-group antigens on a donated kidney can be enzymatically removed well enough to temporarily prevent the catastrophic immediate rejection expected from a major ABO mismatch.
That turns a long-standing transplant barrier into something researchers may eventually be able to engineer around.
For medicine, that is a profound change in perspective.
And for people waiting for donor organs, advances that expand the usable donor pool could ultimately mean something much simpler—and much more important:
more chances to receive the right organ before time runs out.
