British scientists say they have identified a signal molecule made by the body that triggers chronic inflammation in rheumatoid arthritis.

Researchers from Imperial College London say if scientists could block that signal, it might be possible to develop more effective arthritis treatments.

When a microbe infects the body, the body responds by turning on a molecular switch to set the immune system into action, the researchers said. The new findings show a signal molecule called tenascin-C can trigger the same molecular switch and also activate the immune system. High levels of tenascin-C present in joints, therefore, might cause the activated immune system to attack the joint resulting in the persistent inflammation of rheumatoid arthritis, the researchers said.

"We have uncovered one way that the immune system may be triggered to attack the joints in patients with rheumatoid arthritis," said Kim Midwood, lead author of the study, from the college's Institute of Rheumatology. "We hope our new findings can be used to develop new therapies that interfere with tenascin-C activation of the immune system and that these will reduce the painful inflammation that is a hallmark of this condition."

The research is reported in the journal Nature Medicine.