At the American Society for Microbiology meeting held here this week, scientists from the University of Michigan Medical School will present results of experiments with laboratory mice indicating that antibiotic-induced changes in microbes in the gastrointestinal tract can affect how the immune system responds to common allergens in the lungs.

"We all have a unique microbial fingerprint a specific mix of bacteria and fungi living in our stomach and intestines," says Gary B. Huffnagle, Ph.D., an associate professor of internal medicine and of microbiology and immunology in the U-M Medical School. "Antibiotics knock out bacteria in the gut, allowing fungi to take over temporarily until the bacteria grow back after the antibiotics are stopped. Our research indicates that altering intestinal microflora this way can lead to changes in the entire immune system, which may produce symptoms elsewhere in the body."

If confirmed in human clinical studies, Huffnagle believes his research findings could help explain why cases of chronic inflammatory diseases, like asthma and allergies, have been increasing rapidly over the last 40 years a time period that corresponds with widespread use of antibiotics.

To understand the implications of the U-M research, it's important to know something about the complex relationship between the gastrointestinal, respiratory and immune system in the human body.

Every time you inhale, air flows past mucus-producing cells and tiny hairs designed to trap bits of pollen, dust and spores before they enter the lungs. These trapped particles are swept into the stomach with saliva and mucus as you swallow.

"Anything you inhale, you also swallow," Huffnagle says. "So the immune cell
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26-May-2004