rcjohnsen at aol.com
Fri Jan 28 15:40:35 EST 2000
Thymus tissue heals DiGeorge syndrome
in Sci. News 156:328
Nov 20 1999
The rare baby born without a thymus gland can't defend itself. In the
thymus, which sits atop the heart, the body's T cells learn the most important
lessons of immunology: which cells to attack and which to let live. Without a
thymus, a baby had no chance to live beyond a few years, until now.
Infants missing all or part of a thymus have DiGeorge syndrome. Babies with
even a small thymus usually survive.
Researchers at Duke University Medical Center in Durham, N.C., have
implanted thin slices of thymus tissue into the thigh muscles of
2-to~month-old babies with DiGeorge syndrome. The tissue had been removed from
other babies during heart surgery and would otherwise have been discarded.
Because the transplant recipients had no thymus to instruct T cells to attack
the foreign tissue, it wasn't rejected.
T cells proliferated in four of the five recipients. Two of these patients
survived and are now 1 1/2 and 6 years old. The other three died before their
first birthday of infections or abnormalities associated with DiGeorge syndrome
but unrelated to the transplant operation, the researchers report in the Oct.
14 NEW ENGLAND JOURNAL OF MEDICINE.
With DiGeorge syndrome, all the children were destined to get "one
infection after another," particularly pneumonia, says study coauthor M.
Louise Markert, a pediatric immunologist at
Duke. The transplant recipients who survived are now essentially cured.
Getting the operation to work was difficult. One key to success had to do
with the condition of the donated tissue. In previous thymus transplants, which
had failed, researchers apparently didn't prepare the donor tissue properly,
Markert says. Only extremely thin slices would stay alive in the recipients.
"It took me a month just to get the tissue viable," she says.
One mystery remains: The scientists had expected the transplant recipients
to be susceptible to graft-versus-host disease, a dangerous ailment in which
immune cells in transplanted tissue attack their new host. Yet this didn't
happen in the babies who received thymus slices.
"It's a miracle," Markert says. "It's something we don't understand." She
and her colleagues speculate that the immaturity of T cells in the transplant
keeps them from attacking cells
in the children with DiGeorge syndrome. N.S.
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