Gut Bacteria Could Cause Vision Problems

If you think that gut bacteria only affects the digestive system, you’re in for a real eye-opener. A recent study by the National Eye Institute (NEI) found that bacteria in the gut may be responsible for an inflammatory eye disorder called autoimmune uveitis.

Autoimmune uveitis is responsible for about 10 percent of severe visual disability in the United States. It occurs when T cells penetrate the protective blood-ocular barrier and attack proteins in the eye. These T cells must first be activated before they can recognize proteins and attack them, but the activation site has remained a mystery until now.

Senior study author Rachel Caspi, Ph.D., of the National Institutes of Health, explained that activation could take place in the eye itself, but this theory is unlikely, due to the fact that non-activated cells cannot travel in and out of the eye. After eliminating other possibilities, Caspi and her colleagues directed their focus to gut microbes.

Caspi and her team conducted a study on mice to test their gut microbe theory. They found that activated T cells were elevated in the gut but not in the lymph nodes, indicating that T cells are activated in the gut before any signs of disease are present. The researchers then administered antibiotics to the mice in order to eliminate the bacteria in their gut. They discovered that autoimmune uveitis was delayed and much milder in the mice with no gut flora, compared to the mice that had normal gut bacteria.

Similar results were seen in mice that were raised in an environment with no exposure to germs or bacteria. When the mice were moved to a normal environment and they acquired gut bacteria, autoimmune uveitis was much stronger.

While the study’s findings help shed a light on what triggers autoimmune uveitis, Caspi explained that individuals should not take steps to alter their gut bacteria as a form of treatment. “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,” she said.

Caspi and her colleagues will continue their research in order to identify which bacteria is responsible for activating T cells. “If found … we may be able in the future to use this knowledge to selectively eliminate the response that leads to the development of this disease” (Source: Healthline).

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