Researchers at the University of Cambridge successfully altered the blood type of three donor kidneys in a discovery that could significantly improve the chances of patients waiting for a transplant finding a match.

According to scientists, this could improve the number of kidneys available for transplant, particularly among minority ethnic groups who are less likely to find a match.

For example, a kidney transplant from someone with blood type A cannot be transplanted to someone with blood type B, and vice versa. However, changing the blood type to the universal O would allow more transplants as it could be used for people with any blood type.

A normothermic perfusion pump - a device that connects to a human kidney to flow oxygenated blood through the organ to better maintain it for future use - was used by the Cambridge researchers to flush blood injected with an enzyme through the deceased donor's kidney.

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The enzyme eliminated the blood type markers that line the blood arteries of the kidney, converting the organ to type O.

A Ph.D. student at the University of Cambridge, Serena MacMillan, said: “Our confidence was really boosted after we applied the enzyme to a piece of human kidney tissue and saw very quickly that the antigens were removed.

“After this, we knew that the process is feasible, and we just had to scale up the project to apply the enzyme to full-size human kidneys.

“By taking B-type human kidneys and pumping the enzyme through the organ using our normothermic perfusion machine, we saw in a matter of just a few hours that we had converted a B-type kidney into an O type. “It’s very exciting to think about how this could potentially impact so many lives.”

Solution for minorities 

Ethnic minority patients frequently had to wait a year longer for a transplant than white patients, thus the study could have special ramifications for them, according to specialists.

The groups are more likely to have type B blood, and with low donation rates from these groups, there aren't enough kidneys to go around.

In 2020-21, black and minority ethnic donors made up little over 9% of all organ donations in the UK, whereas black and minority ethnic patients make up 33% of the kidney transplant waiting list.

The researchers must now determine how the newly modified O-type kidney will react to a patient's usual blood type in their normal blood supply.

They can accomplish this before testing people because the machine can take kidneys that have been altered to type O and introduce other blood types to see how the kidney reacts.

Why can blood groups be a problem?

Professor of transplant surgery at the University of Cambridge, Prof Mike Nicholson, said: “One of the biggest restrictions to who a donated kidney can be transplanted to is the fact that you have to be blood group compatible. The reason for this is that you have antigens and markers on your cells that can be either A or B."

He continued, “Your body naturally produces antibodies against the ones you don’t have. Blood group classification is also determined via ethnicity and ethnic minority groups are more likely to have the rarer B type.”

After testing the reintroduction of other blood types, the team will look at how the approach might be used in a clinical setting.

The research funded by the Kidney Research UK charity is due to be published in the British Journal of Surgery in the coming months.