Researchers have long known that childhood antibiotic use can impede the normal growth and development of gut bacteria. This, in turn, affects the function of the immune system ― around 70 percent of which is contained in the gut.
The gut is home to trillions of bacteria that play a crucial role in our physical and mental health, including the digestive system, brain and immune system. One side effect of antibiotics is that they can indiscriminately kill off important strains of healthy bacteria alongside the bad bacteria they aim to target.
The new study
Now, a Monash University study involving mice, published in the April issue of the Journal of Leukocyte Biology, shows that using antibiotics early in life may reduce gut bacteria, which could in turn contribute to the development of intestinal inflammation.
“Our intestinal bacteria are now understood to have a major role in shaping immune health and disease, but the details for this process remain poorly understood,” said John Wherry, Ph.D., deputy editor of the journal, in a press release. “These new studies provide an important clue as to how the early signals from our gut bacteria shape key immune cells and how these neonatal events can shape disease potential later in life.”
CD4 T cells are known to play a critical role in the inflammatory response. Dysfunction in these cells is involved in the overactive immune response that eventually leads to the development of chronic inflammatory conditions like Crohn’s, lupus, multiple sclerosis and other autoimmune diseases.
For the study, the researchers treated female mice with the equivalent of more than 100 times a normal human dose of several antibiotics during pregnancy and also treated their pups with the same drugs during their first three weeks of life. A second group of pregnant mice and their pups remained untreated to act as a control.
The pups treated with antibiotics had reduced levels of gut bacteria, as was expected. When the pups were eight weeks old, the researchers examined CD4 T cells from both the treated and untreated groups to examine their ability to induce intestinal inflammation in other mice. The scientists found that immune cells from the antibiotic-treated mice induced a significantly more severe and rapidly forming disease than immune cells from other mice.
Antibiotic-treated mice also had increased stress hormones, which suggests a connection between reduced gut bacteria and stress response.
It’s important to note, however, that the antibiotics’ effects on the mice in the study were reversible. If antibiotic-treated pups were allowed to regain normal gut bacteria populations, the mice that received their immune cells no longer saw an uptick in disease. Those mice’s stress hormone levels similarly reversed, which suggests that “the effects of antibiotics treatment and the gut bacteria are indirect, potentially acting through stress hormones,” according to study author Colby Zaph, head of the Laboratory of Mucosal Immunity and Inflammation at Monash University in Australia.
Beyond the study: Preventing and treating autoimmune disease
The good news is that certain lifestyle changes ― like adopting a gut-healthy diet, managing stress levels and exercising regularly ― could make a real difference for gut, and therefore immune, health.
“We know that gut microbiota are altered by stress, antibiotics, high-fat diet, and a ‘overly clean environment,’” University of Texas associate professor of pediatrics and gastroenterology Dr. Yuying Liu, who has conducted research on gut bacteria and autoimmunity, recently told The Huffington Post. “It is reasonable to postulate that lifestyle interventions could help to prevent or treat autoimmune diseases.”
CORRECTION: This article initially misstated the findings of the Monash study: specifically the study did not identify a correlation between antibiotics use and later adult illnesses, including inflammatory diseases, and the article did not note that the effects of the antibiotics were reversible. This article has been edited accordingly throughout, and has been updated with additional details about the study’s methodology and findings.