A Gut Reaction to Arthritis

Researchers have found that a gut reactionor more precisely, a reaction to a bacteria living in the gutcan trigger a cascade of responses that may ultimately lead to the development of rheumatoid arthritis.

Like most mammals, our gut is home to thousands of species of bacteria, many of which aid in the development of a normal immune system. But some strains of gut-residing bacteria can also play a role in autoimmune disorders. The surprising aspect of this study was the discovery that bacteria in the gut can affect tissue as far removed as the joints.

Researchers from Harvard Medical School and New York University, began by raising arthritis-prone mice in a germ-free environment. At three weeks of age, some mice were transferred to a non-germ-free facility and the researchers introduced segmented filamentous bacteria into their systems. When they introduced this normally-occurring bacteria into the mice, the animals rapidly began producing autoantibodies and developed arthritis within four days.

"In the absence of all bacteria, these mice didn't develop arthritis, but the introduction of a single bacterium was enough to jump-start the immune process that leads to development of the disease," says Mathis, an Harvard Medical School professor of pathology.

First author Hsin-Jung Wu emphasizes that these bacteria do not cause the mice to "catch" arthritis. "It's more that they have the genetic susceptibility, and this bacterium creates an environment that allows this genetic susceptibility to play out," says Wu, a postdoctoral researcher at Harvard Medical School. "It's an interaction between genetics and the environment.""This is an important, rather young, area of investigation," said lead researcher Diane Mathis, a professor of pathology at Harvard Medical School.While the research is preliminary, it's yet to be seen if humans have the same response as mice, it does hold out promise for a new line of treatment for rheumatoid arthritis. "It may eventually be possible to ameliorate or protect from human autoimmune diseases, arthritis and others, by treating with probiotics, antibiotics or other inhibitors of bacterial products," Mathis said.The report is published in the June 25 issue of Immunity.
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