Donor kidneys protect itself in a new body!
Researchers with the Mayo Clinic discover that a donor kidney protects itself
once transplanted into a new body.
A long-standing medical discussion about how transplanted organs survive in a
new body has received provocative new evidence from Mayo Clinic research. It
shows a donated kidney survives in a new body by turning on a protective
mechanism to shield it from the hostile environment of the patient's immune
system. The results are published in this month's American Journal of
Transplantation.
Says Mark Stegall, M.D., head of the transplant team that studied kidney
genes' response to transplantation, "The big question has always been: Why
don't the antibodies injure the kidney? Our study begins to show one possible
reason for that - there's a protective mechanism at work."
In the study, the Mayo Clinic team analyzed which genes are turned on during
the biological phenomenon known as "accommodation" - the process by
which a transplanted organ adapts to the new environment of the donor's body.
Accommodation was first described 20 years ago by Jeffrey Platt, M.D., a Mayo
Clinic transplant biologist and co-author of this current Mayo Clinic study.
James Gloor, M.D., a Mayo Clinic nephrologist and research team member,
describes the significance of the work this way: "It's not that the
recipient's immune system fails to see the organ; it's more that the organ, in
some way, can turn on this protection that allows it to inhabit this otherwise
hostile environment of a new body."
An Accommodation Analogy: Calluses and Blisters
Transplant surgeons want to get to the heart of the accommodation mechanism
so they can manipulate it most effectively and gently. Their goal is to provide
the patient maximum benefit in a transplant with the least side effects.
Says Dr. Gloor, "In biology, most of the time the body can protect
itself from a variety of things." He offers the example of how feet protect
themselves from the friction of new shoes that cause blisters by producing
protective skin thickenings: calluses. "Once your feet have calluses, you
can walk around with your shoes and you don't develop blisters anymore. The
reason you can is that your foot has accommodated to that hostile
environment," he says.
Drs. Stegall and Gloor say a similar protective response appears to occur
during kidney transplantation. For example, when one kidney is removed from the
donor, that leaves the donor with a single functioning kidney which senses that
it needs to do more work. "We can see it will get bigger so it can do more
work. It's compensating for the fact that it's the only one there,'' Dr. Gloor
explains.
The Experiment
To try to observe the mechanisms at work in accommodation, the Mayo Clinic
team used a molecular biological technique that allowed them to look at which
genes were expressed in kidney transplants in which the donor's and patient's
immune systems were compatible. They then contrasted the compatible-transplant
gene expression patterns with genes expressed in kidney transplants that were
immunologically incompatible.
The Results
Different gene-expression patterns occurred in different situations. Says Dr.
Stegall, "We found that there was a wide array of entirely different genes
turned on -- or turned off -- in the incompatible transplants that were not
changed in regular kidney transplants. It implies that something is happening in
the incompatible kidney. From the results, it seems likely that the kidney is
'accommodating' to the otherwise destructive antibodies
by developing processes that actually protect it." Accommodation, he adds,
may actually be a fairly general phenomenon present in a variety of human
diseases.
More information
e-mail: newsbureau@mayo.edu
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