Eye Disease Could be Caused by Gut Bacteria

Digestive SystemEven though your eyes are not located anywhere near your digestive system, it seems that there may be a connection between your vision and your gut. According to the National Eye Institute (NEI), a study on mice found that gut bacteria could cause autoimmune uveitis, an inflammatory eye condition that is responsible for about 10 percent of significant visual disability in the United States. Autoimmune uveitis occurs when the immune system behaves erratically and attacks certain eye proteins.

Rachel Caspi, Ph.D., of the National Institutes of Health, said that researchers had disproved most sources for bacterial invasion of the eye, and speculation finally rested on retina-specific T-cells that are activated in the intestines.

Once T-cells are activated, they can penetrate the blood-tissue barrier that separates the eye from the rest of the body and attack specific eye proteins that do not exist anywhere else in the body.

In the mice study, levels of activated T-cells were not elevated in the lymph nodes as the researchers would suspect, but they were extremely elevated in the intestines. This led the team to believe that T-cells may have been activated in the intestines before any symptom of eye disease occurred. To test their hypothesis, the team administered antibiotics to eliminate a wide range of bacteria in the gut. As a result, the mice without gut bacteria developed autoimmune uveitis much later and less acutely than mice with normal gut bacteria.

Caspi and her team are enthusiastic about the prospect of understanding what triggers autoimmune uveitis because this knowledge will ultimately help uncover safer treatments for long-term health. Corticosteroids are effective in reducing inflammation, but their extended use can result in negative side effects.

“These findings will allow us to understand the biological basis for the disease,” Caspi said. “The findings should in no way be interpreted that a patient can pop a probiotic pill and their disease will improve, or that they should start taking antibiotics to eliminate commensal bacteria.”

Caspi said that there is no “quick fix” to prevent or eliminate bacteria from attacking the retina, but she and her team are working on a solution. Their hope is to identify a bacterium that has a protein that imitates the retinal antigen to selectively eliminate the response that leads to autoimmune uveitis (Source: Healthline).


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