Densensitization Procedure Helps Hard-to-Match Kidney
WEDNESDAY, July 27 (HealthDay News) -- A combination therapy
that "desensitizes" kidney transplant recipients could help
hard-to-match patients find a needed kidney faster.
The desensitization procedure combines the use of plasmapheresis
-- a machine that filters the blood plasma to remove antibodies --
and low-doses of a medication called intravenous immune globulin
The combination of these therapies improves survival rates
dramatically. Eight years after receiving a transplant, survival
rates were 81 percent for those who received the treatment compared
to just 31 percent for people who had to stay on dialysis, new
"This is a huge unmet problem. There are probably as many as 30,000 people who have been exposed to foreign tissue waiting for a kidney. They're really hard to match," explained study author Dr. Robert Montgomery, director of the comprehensive transplant program at Johns Hopkins Hospital and a professor of surgery at Johns Hopkins University School of Medicine in Baltimore.
"This therapy will allow earlier transplantation for someone who's hard to match. This is one of those rare things in health care that's a win-win. It will save money long-term and improve quality-of-life," he said.
Results of the study are published in the July 28 issue of the
New England Journal of Medicine.
The problem with these particular patients is that they've been
"sensitized" to substances known as human leukocyte antigens (HLA).
Everyone has six of these antigens, which are proteins found on
white blood cells. You inherit three antigens from each parent,
according to the National Kidney Foundation. When a kidney patient
is evaluated for a transplant, doctors try to match as many of
those antigens as possible, to improve the chance of a successful
But, some people have been exposed to other antigens, which can
cause the body to develop antibodies (become sensitized) to HLA.
This can happen during pregnancy, a blood transfusion or previous
transplantation. If exposed to that particular foreign antigen
again, the HLA antibodies will destroy any tissue containing it.
This severely limits the number of eligible transplant donors for a
recipient who is sensitized.
In an attempt to overcome this significant problem, Montgomery
and his colleagues began recruiting HLA-sensitized potential kidney
transplant recipients. From 1998 through 2009, the researchers
treated 211 HLA-sensitized people waiting for transplants with the
desensitization procedure. More than half of this group had already
had one kidney transplant.
Plasmapheresis works much like dialysis. In dialysis, blood is
removed from the body, filtered to remove waste and returned to the
body, newly purified. In plasmapheresis, the blood is separated to
remove the plasma, which contains the antibodies. The remaining
portion of the blood is returned to the body along with plasma
donated from a healthy person. Because this process removes
antibodies, it can leave people vulnerable to infection. To combat
this potential side effect, the researchers gave small doses of the
immune-boosting drug IVIG.
The HLA-sensitized patients received an average of four
plasmapheresis sessions before transplant and five after
transplant, according to the study.
The researchers compared these patients to two other groups of
matched control subjects. One group stayed on dialysis, while the
other group either stayed on dialysis or had an HLA-compatible
During the first year after transplant, survival rates were
similar among the three groups. After three years, the survival
rate was 85.7 for the desensitized group compared to 67.2 percent
in the dialysis-only group and 77 percent for the dialysis or
By five years, estimates of patient survival were 81 percent for
the desensitization group, 52 percent for the dialysis-only group
and 66 percent for the dialysis or transplantation group.
"This is the first study to show this dramatic improvement for desensitization," said Montgomery. "It also shows how lethal kidney disease is if you don't get a transplant."
Dr. David Butcher, a transplant nephrologist at St. John
Hospital and Medical Center in Detroit, said the findings were
"very exciting, with the potential to help a good number of the
people who are waiting for transplant. This gives hope that they'll
be able to get off dialysis much sooner."
But, the findings will need to be replicated in other transplant
centers before the treatment could become more widely adopted, he
said. And, surgeons must also be concerned with infections and
long-term rejection rates, which weren't studied here, he
Learn more about kidney transplantation from the
U.S. National Kidney and Urologic Diseases
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