Stress not only sends the human immune system into overdrive - but it can also wreak havoc on the trillions of bacteria that work and thrive inside our digestive system, says a new research.
Michael Bailey, an assistant professor of dentistry and member of the Institute for Behavioral Medicine Research at Ohio State University and colleagues turned to mice to better understand the roles that bacteria play in immune balance. They ran a series of experiments using a common stressor for these animals.
From the intestinal samples, Bailey's team could determine the relative proportion of at least 30 types of bacteria residing there.
Compared to the control mice, the stressed animals showed two marked differences: The proportion of one important type of bacteria in the gut - Bacteroides - fell by 20 to 25 percent while another type - Clostridium - increased a similar amount. Also, levels of the two biomarkers, IL-6 and MCP-1, jumped 10-fold in the stressed mice, compared to controls.
The researchers then treated stressed mice with broad-spectrum antibiotics that could kill as much as 90 percent of the intestinal bacteria for a short period. When they again looked at the two immune biomarkers in the stressed mice, they saw only a doubling of IL-6 and MCP-1 - an increase only one-fifth as much.
"We know now that if we knock the population of bacteria down with antibiotics, we don't have the same innate immune response," said Bailey.
"That showed that the bacteria are involved in the ability of stress to prime the innate immune system," added Bailey.
He said that the research shows that some of the changes in systemic immunity in the body can be influenced by changes in these bacterial colonies, a result that reinforces the idea that they have a broader effect on the immune response.
The study is detailed in the current issue of the journal Brain, Behavior and Immunity.