New research has found that friendly bacteria found in the human digestive tract help rally the immune system against the parasite responsible for toxoplasmosis.

Toxoplasmosis is a disease caused by protozoan Toxoplasma gondii that mostly affects cats but can also be transferred to humans. Although the infection is typically mild, it can be dangerous for those with a weakened immune system, or for pregnant women and their fetuses.

Researchers from the University of Texas Southwestern Medical Center found that T. gondii induces the good bacteria to send activating signals to toll-like receptors – a type of immune protein – which produces an inflammatory response against the pathogen.

“We speculate that because commensal bacteria co-evolved with the host, they must have found this fine balance to induce the sufficient stimulatory effects of the immune system without causing illness or death,” says Dr. Felix Yarovinsky, assistant professor of immunology at UT Southwestern and senior author of the study.

“The fact that commensal bacteria vary dramatically from person to person might explain why therapeutic outcomes vary so much,” he adds.

Those who would like to boost the amount of good bacteria in their digestive system may turn to nutritional supplements containing probiotics.