A new study from scientists at The Ohio State University has revealed a surprising link between gut bacteria and rheumatoid arthritis (RA), a painful autoimmune disease that affects millions of people worldwide. The research shows how certain helpful bacteria in the gut can trigger changes in the immune system that may lead to RA and possibly other autoimmune diseases.
Rheumatoid arthritis affects about 18 million people globally. It causes the immune system to mistakenly attack the body’s own joints, leading to inflammation, swelling, and chronic pain.
Although doctors have long known that genes and environmental factors like smoking play a role in RA, researchers are now discovering that changes in gut bacteria—normally considered helpful—may also be part of the cause.
The story starts in the gut, where a group of microbes called commensal bacteria usually live peacefully and support good health.
But in a 2016 study, scientists found that some of these microbes could activate a type of immune cell called T cells in a way that worsened autoimmune disease in mice. Now, years later, they have traced the full path of these cells and found out how this process works.
The key immune cell in this study is a rare type called a TFH17 cell. It is a hybrid cell that acts partly like a T follicular helper (TFH) cell and partly like a T helper 17 (TH17) cell.
Normally, TFH cells stay in one spot—inside lymph nodes—to help another type of immune cell, B cells, do their job. But these hybrid TFH17 cells are different. They travel around the body and create inflammation, which can be very harmful if you have an autoimmune condition.
Researchers used genetically engineered mice to trace the journey of these cells. They found that the cells begin as regular TH17 cells in the small intestine, specifically in an area called Peyer’s patches.
There, a harmless gut microbe called segmented filamentous bacteria (SFB) causes these cells to change into the more dangerous TFH17 type. This process, called T cell plasticity, allows the immune cells to switch roles depending on their surroundings.
The scientists then used glowing markers to track the movement of these cells in mice with RA. They watched the TFH17 cells travel from the gut to other parts of the body, where they activated B cells more strongly than normal. This caused more inflammation and worsened arthritis symptoms.
To test just how harmful these hybrid cells were, the team did an experiment. They gave one group of mice only normal TFH cells, and another group a mix of normal cells and 20% TFH17 cells.
The second group developed much worse arthritis, with nearly five times more joint swelling than the control group. This showed that even a small number of these hybrid cells can do a lot of damage.
When researchers looked closely at the genes active in these harmful TFH17 cells in mice, they found something even more exciting: the same gene patterns showed up in immune cells from human RA patients. This suggests that what happens in mice may also be happening in people.
Professor Hsin-Jung Joyce Wu, who led the study, said that finding this same “gut signature” in people is a big step forward. It means that the cells scientists studied in mice are likely playing a role in human autoimmune diseases too.
She believes this discovery opens the door to new treatments—not just for RA, but possibly for other conditions like lupus, where similar cells have been found.
In summary, this research shows that even good bacteria in the gut can go bad under certain conditions, triggering immune cells to become harmful and travel through the body to cause inflammation.
It also highlights how the gut is not just important for digestion, but also plays a central role in controlling our immune system. By targeting these hybrid TFH17 cells in future treatments, doctors may one day be able to stop autoimmune diseases before they do serious harm.
If you care about arthritis, please read studies about extra virgin olive oil for arthritis, and pomegranate: A natural treatment for rheumatoid arthritis.
For more information about arthritis, please see recent studies about how to live pain-free with arthritis, and results showing medical cannabis may help reduce arthritis pain, back pain.
The research findings can be found in Nature Immunology.
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