This past week researchers published a paper [media summary] that helps clarify the connection between gut bacteria and the type of system-wide allergic inflammation responsible for asthma and, often, eczema.
David Artis and colleagues at the University of Pennsylvania (the team includes members from Japan and Germany) find that killing off gut bacteria in mice, using antibiotics, results in much higher levels of IgE antibodies and increased populations of basophils, a type of white blood cell involved in allergic inflammation.
Trillions of commensal bacteria live in our intestines, along with other types of less-numerous microbes. Decreases in numbers or diversity of these bacteria are associated, in children, with increased risk of developing allergic disease. Commensal microbes help us digest our food. They are integrated into other processes as well, including the immune system. They have to be. They need to suppress immune reactions that would otherwise destroy them.
Artis and colleagues pointed out that high IgE levels are associated with increased basophil populations in human patients with "hyperimmunoglobulinemia E syndrome," who are at high risk of developing eczema.
The researchers weren't able to specify which species of bacteria are most important in regulating IgE and basophils, but they did show that chemical signals from commensal bacteria normally limit the number of basophils that develop from the bone marrow.
This research supports the idea that overuse of antibiotics in children makes them more likely to develop atopic disease. Far in the future, this work could result in anti-inflammatory therapies based on the chemical signals that gut bacteria use to suppress basophils.