Antibiotics and Allergies?
U-M research suggests microbial changes may be a link
If allergies are making your life miserable and you’ve recently taken
antibiotics, the source of your problem may not be your stuffed-up head. It
could be the microbes in your gastrointestinal tract.
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Mairi Noverr and Gary Huffnagle
Photo: Martin Vloet |
New research by U-M Medical School scientists Gary B. Huffnagle, Ph.D., and
Mairi C. Noverr (Ph.D. 2002) suggests there’s a direct connection between
microbial changes in the GI tract, caused by antibiotics, and 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 Huffnagle,
an associate professor of internal medicine and of microbiology and immunology.
“Antibiotics knock out bacteria in the gut, allowing fungi to increase
temporarily until the bacteria grow back after the antibiotics are stopped.
Our research indicates that these alterations in intestinal microflora can lead
to changes in the entire immune system.”
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An allergic response in the airways of a mouse. The dark staining is excess mucus being secreted into the airways — a result of the underlying allergic inflammation. Courtesy: Gary B. Huffnagle |
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Aspergillis fumigatus mold releasing its tiny spores.
Courtesy: Gary B. Huffnagle |
Noverr, a U-M research fellow, and Huffnagle used laboratory mice in their
experiments, but if the results are confirmed in humans, they believe this research
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.
When we inhale, air flows past mucus-producing cells and tiny hairs designed
to trap bits of pollen, dust and spores before they enter the lungs, Huffnagle
explains. These trapped particles are swept into the stomach with saliva and
mucus as we swallow, exposing immune cells in the GI tract to airborne allergens.
This triggers the production of regulatory T cells that modulate the response
of allergic T cells to incoming allergens in the lungs and sinuses.
When antibiotics disrupt the normal mix of bacteria and fungi in the GI tract,
Huffnagle says this somehow interferes with the ability of regulatory T cells
to dampen the immune system’s response to respiratory allergens. The result
is a hyperactive immune response, which can produce allergy symptoms or even
asthma.
“If we can determine exactly how microflora in the GI tract affect the
immune system, it may be possible one day to prevent or treat allergies and
inflammatory diseases with diet changes or probiotics — dietary supplements
of ‘healthy’ bacteria designed to restore the normal balance of
microbes in the gut,” Huffnagle adds.
Until then, Huffnagle emphasizes the importance of a healthy low-sugar diet,
with lots of raw fruits and vegetables, after taking antibiotics to help restore
the normal mix of microbes in your GI tract as quickly as possible. “The
old saying ‘an apple a day keeps the doctor away’ may be more true
than we thought,” he says.
Huffnagle’s research has been funded by the National Institutes of Health
and a New Investigator Award from the Burroughs-Wellcome Fund. Other collaborators
in his research include Galen B. Toews, M.D., professor of internal medicine;
Nicole Falkowski, Rachael Noggle and Rod McDonald, Ph.D., research associates
in internal medicine.
—SFP
Read an expanded version of this story:
www.med.umich.edu/opm/newspage/2004/allergies.htm
For patient information on allergies:
www.med.umich.edu/1libr/aha/umalerg03.htm
 
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