Scientists have long suspected that bacteria in the gut might play a role in autoimmune diseases, like lupus. But exactly how these bacteria affect the immune system has remained unclear.
Now, researchers from Yale have found that a specific bacterium, called Enterococcus gallinarum, can move from the gut to other parts of the body and cause an immune system overreaction. This discovery may help doctors find better ways to diagnose and treat autoimmune diseases. The study was published in Science Translational Medicine.
How Gut Bacteria Can Cause Harm
The human body is home to trillions of bacteria, collectively known as the microbiome. Many of these bacteria are helpful, aiding in digestion and supporting overall health. But sometimes, bacteria that normally live harmlessly in the body can turn harmful under certain conditions. These bacteria are called pathobionts.
One such pathobiont is E. gallinarum. This bacterium has been linked to lupus in both mice and humans. Previous studies have shown that E. gallinarum can be found in tissues outside the gut in people with lupus. But until now, scientists didn’t fully understand how it might be triggering the disease.
What the Researchers Discovered
The Yale research team, led by immunology experts Noah Palm and Martin Kriegel, studied E. gallinarum using both human cells and mouse models. They found that this bacterium doesn’t just stay in the gut—it can travel to other parts of the body. First, it moves to the lymph nodes and liver, then eventually reaches the spleen.
The spleen and lymph nodes are key parts of the immune system, responsible for detecting threats and launching immune responses. The researchers believe that once E. gallinarum reaches these organs, it triggers an immune overreaction, leading to the development of autoimmune diseases.
How the Immune System Overreacts
Normally, the immune system defends the body by attacking harmful invaders like viruses and bacteria. But in autoimmune diseases, the immune system mistakenly attacks healthy tissues instead.
The researchers found that E. gallinarum causes the immune system to produce a specific type of immune cell called T helper 17 (TH17) cells. These cells can become highly inflammatory and push other immune cells to mature.
In turn, these mature immune cells start producing autoantibodies—antibodies that mistakenly attack the body instead of harmful microbes.
This chain reaction may explain how autoimmune diseases like lupus begin.
A Step Toward Better Treatments
Autoimmune diseases are difficult to treat because scientists don’t fully understand what causes them. “One problem with autoimmune diseases is that we don’t really know how they start,” said Kriegel. “But these findings help us piece together this puzzle.”
This study suggests that E. gallinarum could be used as a biomarker—a sign that someone is at risk for developing an autoimmune disease. More importantly, the findings open the door to new treatment strategies. Instead of only targeting the immune system (as current treatments do), future therapies might also target harmful gut bacteria like E. gallinarum.
“Maybe in the future, we wouldn’t just target the immune system when treating autoimmune diseases,” Kriegel said. “We may also be able to target the triggering bacteria as well.”
By understanding the role of gut bacteria in autoimmune diseases, researchers may one day develop better treatments that prevent these conditions before they even begin.
If you care about health, please read studies that vitamin D can help reduce inflammation, and vitamin K could lower your heart disease risk by a third.
For more health information, please see recent studies about new way to halt excessive inflammation, and results showing foods that could cause inflammation.
The research findings can be found in Science Translational Medicine.
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