Gut bacteria link to uveitis

Microbes living in our guts could be a driving force of uveitis, according to new research. Scientists at the National Eye Institute (NEH) in Bethesda, US, discovered that commensal bacteria – the typically benign microbiota lining our gut – may be triggering immune cells in the retina, resulting in automimmune uveitis. 

The group found that mice that spontaneously developed the condition had high numbers of activated T cells in their guts. In addition, protein extracts from the gut activated T cells in the retina.

Treating the mice with antibiotics reduced T cell numbers while delaying and reducing the severity of uveitis.

The findings indicate that the gut bacteria are producing a molecule which mimics the activity of a retinal protein, activating retina-specific T cells and enabling them to cross the blood-retina barrier and cause damage. The findings could have significance for treating immune conditions, such as uveitis, in humans. 

Dr Rachel Caspi, of the NEH and senior author of the study, said that if the variety of bacteria in our guts could mimic a retinal protein “they could also mimic other self-proteins that are targets of inappropriate immune responses elsewhere in the body.”

She added that if researchers can identify the specific bacteria, and the mimic signals they are producing “we may be able to use this knowledge to selectively eliminate the responses that lead to the development of this disease.” 

The findings are published in the journal Immunity.