Rheumatoid arthritis, often called RA, is a long-term autoimmune disease that affects millions of people around the world.
Unlike the wear and tear seen in osteoarthritis, rheumatoid arthritis develops when the body’s immune system mistakenly attacks its own healthy joints. This causes pain, swelling, stiffness, and warmth in the joints, especially in the hands, wrists, and feet.
Over time, the disease can damage cartilage and bone, making it difficult for people to move and carry out everyday tasks.
Although medicines can help control the disease, there is currently no cure, and scientists have been searching for the events that start the illness in the first place.
For many years, researchers have suspected that the trillions of bacteria living in the human gut may influence autoimmune diseases.
These bacteria, known collectively as the gut microbiome, help digest food, produce vitamins, and support the immune system. Most of the time they are beneficial, but changes in the balance of gut bacteria have been linked to conditions such as inflammatory bowel disease, obesity, diabetes, and autoimmune disorders.
Until now, however, it has been difficult to identify exactly which bacteria might contribute to rheumatoid arthritis.
A new study led by scientists at the University of Colorado, together with researchers from several other institutions, has provided some of the strongest evidence yet that one specific type of gut bacteria may help trigger rheumatoid arthritis in people who are already at high risk of developing the disease. The findings were published in the journal Science Translational Medicine.
The researchers focused on people who had early warning signs of rheumatoid arthritis but had not yet developed swollen or painful joints. These individuals carried blood markers, including certain antibodies, that are known to increase the risk of developing RA in the future.
Studying this group allowed the scientists to investigate what might happen before the disease fully appears.
To identify possible bacterial triggers, the team collected blood samples and stool samples from these volunteers. They isolated antibodies from the blood and mixed them with bacteria taken from the stool samples. This clever approach allowed the researchers to see which bacteria the immune system was already recognizing as a possible threat.
The experiments revealed one previously unrecognized bacterial species that strongly attracted the attention of the immune system. To find out whether this bacterium could actually contribute to disease, the researchers introduced it into the intestines of laboratory animals.
The results were remarkable. Animals exposed to the bacterium developed the same blood markers that are commonly found in people who are at risk for rheumatoid arthritis. Some of the animals later went on to develop symptoms that closely resembled rheumatoid arthritis itself.
This suggested that the bacterium was not simply associated with the disease but could actually help trigger the abnormal immune response.
The scientists then looked more closely at immune cells called T cells, which play a major role in directing the body’s immune defenses. They found that T cells from people with rheumatoid arthritis reacted strongly when exposed to this particular bacterium. In contrast, T cells collected from healthy individuals showed little or no response.
This finding suggests that people who are genetically or biologically vulnerable to rheumatoid arthritis may react to this gut bacterium in a unique way, setting off the chain of events that eventually leads to joint inflammation.
These findings are exciting because they open up the possibility of preventing rheumatoid arthritis before permanent joint damage begins. If future studies confirm that this bacterium plays a direct role in triggering the disease, doctors may eventually be able to target it with medicines or other treatments designed to change the gut microbiome.
Such approaches could stop the harmful immune response before rheumatoid arthritis develops.
The researchers emphasize that more work is needed before this discovery can be turned into new treatments.
Scientists still need to understand exactly how the bacterium activates the immune system and why only certain people respond to it. Clinical studies in humans will also be needed to confirm whether removing or changing this bacterium can lower the risk of developing rheumatoid arthritis.
The project took five years to complete and relied on volunteers who knew they were at increased risk for rheumatoid arthritis and agreed to participate in the research. Their contribution has helped scientists move closer to understanding one of the biggest unanswered questions in autoimmune disease research.
The study was led by Dr. Kristine Kuhn and published in Science Translational Medicine. If future research confirms these findings, targeting specific gut bacteria could become an entirely new strategy for preventing rheumatoid arthritis before painful joint damage ever begins.
If you care about pain, please read studies about vitamin K deficiency linked to hip fractures in old people, and these vitamins could help reduce bone fracture risk.
For more health information, please see recent studies that Krill oil could improve muscle health in older people, and eating yogurt linked to lower frailty in older people.
Copyright © 2026 Knowridge Science Report. All rights reserved.
