By E.J. Mundell
NEW YORK -- Studies in mice suggest that a compound linked to rheumatoid arthritis is found throughout the body -- not just in the joints.
Researchers say that the finding could lead to better understanding and treatment of the debilitating joint disorder.
If the discovery is replicated in humans, it could lead to "vaccination
therapies" aimed at preventing the immune system dysfunction that causes
rheumatoid arthritis, senior study author Dr. Diane Mathis, of Harvard Medical
School in Boston, Massachusetts, told Reuters Health. She and her team published
their results in the November 26th issue of the journal Science.
Mathis, along with colleagues Drs. Isao Matsumoto, Adrien Staub, and
Christophe Benoist, examined the tissues of mice affected by rheumatoid
arthritis. In this disease, the immune system reacts against the body's own
tissues to cause joint swelling and pain, and even the destruction of a joint.
The scientists discovered that the presence in cells of a specific enzyme,
called glucose-6-phosphate isomerase (GPI), helped trigger the arthritic immune
response.
Previously, researchers had assumed that any rheumatoid arthritis antigen
would reside only in joint tissue, the part of the body that the disease
targets.
But Mathis told Reuters Health that, "surprisingly," the enzyme appears to
be spread throughout the entire body.
So why does rheumatoid arthritis focus on the joints alone? "First,"
Mathis said, "it could be that, even though GPI is found in all cells, perhaps
there is a modified form that is expressed specifically in the joints -- or
perhaps (in) unusually high amounts."
Alternatively, she said, the unique structure and physiology of joints
might lead to a "trapping" of immune agents that react with GPI to produce
inflammation.
In any case, the authors say, the discovery suggests that the mechanism
behind rheumatoid arthritis -- at least in mice -- is "fundamentally different"
from what was previously thought to happen.
"We have to prove that this mechanism is indeed relevant to human
(rheumatoid arthritis) patients," Mathis stressed. But she believes that if
researchers can pinpoint similar pathways in humans, the discovery could lead to
whole new targets for future therapies aimed at controlling the disease.
Mathis and her colleagues conducted the research while at the Institut de
Genetique et de Biologie Moleculaire et Cellulaire in Strasbourg, France.
