Good bacteria DNA fights infection

BETHESDA, Md., Oct. 3 (UPI) -- U.S. researchers say the DNA of so-called "good bacteria" that normally live in the intestines help defend against infection.

The study, published in the journal Immunity, was conducted in the Laboratory of Parasitic Diseases at the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, in Bethesda, Md.

Between 300 to 500 species of beneficial bacteria -- known as commensals -- in the intestines help maintain digestive health and protect against harmful bacteria, known as pathogens.

"Pathogens often behave similarly to gut commensals," study leader Yasmine Belkaid says in a statement. "Because the body needs commensals but also has to rid itself of disease-causing microbes, the immune system must distinguish the good bugs from the bad ones."

Belkaid's team describes how receptors on some intestinal cells -- known as Tregs -- are regulated to facilitate an immune response to a pathogen. They found that during an infection, the DNA of the body's beneficial bacteria binds to a specific receptor on the intestinal immune cells, called TLR9.

The binding of commensal DNA to TLR9 in the presence of a pathogen prevents the generation of Tregs in favor of the generation of protective cells that clear the body of the invading pathogen.