Another piece of the RA puzzle?

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Another piece of the RA

puzzle?

Experts believe that rheumatoid arthritis (RA)

occurs when cells that normally defend the body from illness and injury instead

mistakenly attack cartilage and joints. But what, exactly, are the misguided

immune cells after? That’s never been established, but most scientists

suspected that the object of the attack was collagen, a protein in cartilage,

bone, and other connective tissues. According to new research, however, the

target may be a carbohydrate.

No nutrition connection

The specific carbohydrate involved in the

immune cell attack is what scientists call a glycosaminoglycan

(GAG). It is NOT the same as the carbohydrate we get from food. Rather,

it’s part of the structure of cartilage and joint fluid, as well as of

skin and other connective tissues.

Intriguing findings

The new information comes mainly from studies

in which Boston researchers injected GAGs into the

tails of laboratory mice. After a few injections, the mice developed arthritis-like

swelling and redness around their joints. Examination of the inside of the

joints showed that the synovial membranes (the joint

linings that secrete lubricating fluid) were overrun by white blood

cells—immune system soldiers not normally found in joints or joint fluid.

And, the white cells were attacking GAGs!

The research teams have taken their studies

further. They developed a test to identify immune cells that home in on GAGs. The test found substantial numbers of these cells in

joint tissue taken from people with RA.

Only the beginning

More and larger studies must be done before

doctors accept the notion that GAGs are involved in

RA. And, many questions remain—including why GAGs

become a target in people with RA. Still, experts say the discovery could open

up new lines of research and possibly lead to the development of drugs that

attack the disease in a different way.

From The Journal of the

American Medical Association

Published: May/Jun 2004