New Clue to Autoimmune Diseases Found

Same antibody found in Grave's disease shows up in rheumatoid arthritis

MONDAY, Aug. 23, 2004 (HealthDayNews) -- A single biological mechanism could activate a variety of autoimmune diseases, researchers report.

The discovery could pave the way for new therapies for rheumatoid arthritis and other disorders of the immune system, said the authors of a study in the Sept. 1 issue of the Journal of Immunology.

"We knew that the same folks tended to get these diseases, but we didn't know the biology underlying that," explained senior study author Dr. Terry Smith.

Other experts are not certain this represents a one-stone-kills-more-than-one-bird scientific breakthrough. "If that were true, then you would think you would have more patients with autoimmune thyroid disease and rheumatoid arthritis," said Dr. Clifton Bingham, director of the Seligman Center for Advanced Therapeutics at the New York University Hospital for Joint Diseases in New York City.

In autoimmune disorders such as rheumatoid arthritis and Graves' disease, the body's immune system goes awry and begins attacking its own tissues.

This study is an outgrowth of previous research done by the same group on Graves' disease, a thyroid disorder where an antibody causes the gland to overproduce thyroid-stimulating hormone (TSH). "The antibody mimics the action of TSH and causes the thyroid gland to become big and overactive," explained Smith, a professor of medicine at UCLA's David Geffen School of Medicine and head of molecular medicine at Harbor UCLA Medical Center.

But Smith said he didn't believe this explained other symptoms, such as bulging eyes, which people with Graves' disease have.

During their initial research, they found another antibody that could mimic insulin-like growth factor 1 (IGF-1).

They have now found this antibody in people with rheumatoid arthritis as well. The antibody turns on the receptor for IGF-1 which in turns triggers the production of immune T-cells and directs them to the area of inflammation.

According to the Arthritis Association, rheumatoid arthritis is a systemic disease affecting the whole body, triggering inflammation in the lining of the joints and/or other internal organs. Inflamed joint linings can damage bone and cartilage.

"Basically, [Smith] appears to have identified antibodies in the blood of patients with rheumatoid arthritis that act on cells in the joint area and appear to activate a receptor for insulin-like growth factor that cause cells to release cytokines to attract T-cells," Bingham said.

The antibody "starts the ball rolling," Smith added, eventually propelling T-cells to migrate to the affected joint.

"It could be involved in other autoimmune disorders; we're thinking about a large number of diseases," Smith added. "We think that this realization can potentially lead to the development of therapeutics."

Bingham, however, cautioned that the data was preliminary. "It's intriguing and it certainly is something that makes you look forward to additional data in understanding both the occurrence of these in larger number of patients and in trying to understand mechanistically how this process occurs."

More information

The National Institute of Allergy and Infectious Diseases has more on autoimmune diseases.

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