X-Message-Number: 11869
Date: Tue, 01 Jun 1999 15:44:43 -0400
From: Jan Coetzee <>
Subject: thymus gland. New info.

Death-Defying Gland Surprises Medical World: Thymus
Tuesday, June 01, 1999

MSNBC NEWS SERVICES  -  An immune system gland once thought to be
inactive
in adults actually continues to function late in life, according to
research
that could lead to new ways of reactivating the natural defenses of AIDS

and
cancer patients. UNTIL NOW, anatomy experts had concluded the thymus
gland,
a small, thin organ located behind the breastbone, stopped producing the

so-called T-cells of the immune system as individuals aged.

 In their study, the medical detectives, led by Dr. Beth D. Jamieson of
the
University of California at Los Angeles (UCLA), determined from a number
of
tests that the organ continues fielding replacement immune cells in
people
as old as 56.

 The research reported Thursday in the journal Immunity suggests that
although the gland's productivity slows with age, it remains active
nonetheless.  "It gives us hope that if we can find ways to boost up the

activity of the thymus, we could speed up the replacement of T cells"
lost
to the AIDS virus, Jamieson said. "There's still a source available for
T
cells, which was not thought to be the case previously." Drugs also
could
be
developed for cancer patients whose immune systems have been destroyed
by
chemotherapy. But tests of possible treatments are at least two years
away,
Jamieson said.

THE THYMUS TEST

 To test the possibility that the thymus keeps educating cells past
adolescence, Jamieson's team examined gland tissue from 14 people,
either
organ donors or individuals who underwent open-heart surgery. The donors

ranged in age from 1 to 56. Upon examination, the researchers determined

that all the thymus samples contained similar amounts of a marker
associated
with immature T-cells, indicating that gland tissue produces new disease

fighters at all ages.

 Following this, they added tissue from adult samples to a test tube
containing new T-cells. Over six day's time, the cells started
displaying
the chemical markers of more mature immune cells, whereas a comparison
test
tube without any of the sample tissue showed no signs of going through
the
immune-system boot camp.

 Furthermore, a relatively new T-cell receptor test provided by team
members
from the University of Texas Southwestern Medical Center in Dallas
revealed
that blood samples of 45 healthy adults contained brand-new T-cells from

the
thymus.

 David Schwartz, professor of molecular microbiology-immunology at the
Johns
Hopkins School of Public Health, said the study offers important
information
that will be "very useful for understanding how we can generate new
immune
responses as we get older."

 "It means we don't have to rely on T cells that are produced in the
first
decade of our lives," he said.

 Previous studies showed that new T cells were being produced by AIDS
patients who had been taking potent combinations of AIDS drugs. But it
was
not known where in the body those cells were being created.

  OBVIOUS IN HINDSIGHT

 "It's surprising on one hand, but on the other it seems obvious in
hindsight," said Carl Dieffenbach, associate director of the basic
science
program at the National Institute of Allergies and Infectious Disease in

Bethesda, Md. "After all, we'd probably drop dead at age 50 if we didn't

get
new T-cells from somewhere." He predicts the research will "open up
whole
new areas of immunology research to treat all kinds of diseases, not
just
HIV."

 "In terms of total longevity, who knows," he added. "Perhaps diseases
like
Alzheimer's have an immune system component we've missed until now, that
a
more active thymus might correct."

The Associated Press and the Medical Tribune News Service contributed to

this report.
_

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