Gut Bacteria Protects Against Food Allergies, Study


Clostridia, a common class of gut bacteria, protects against food allergies, according to a new study by the University of Chicago Medical Center.

The researchers said that by inducing immune responses that prevent food allergens from entering the bloodstream, Clostridia minimizes allergen exposure and prevent sensitization. The finding now paves the way for developing probiotic therapies for this, so-far untreatable, potentially life-threatening disease.

Food allergies affect 15 million Americans including one in 13 children. The food allergy rates among children have increased by approximately 50 percent between 1997 and 2011. Although the causes of food allergy are unknown, previous studies showed that modern hygienic or dietary practices may disturb the body's natural bacterial composition.

"Environmental stimuli such as antibiotic overuse, high fat diets, caesarean birth, removal of common pathogens and even formula feeding have affected the microbiota with which we've co-evolved," said study senior author Cathryn Nagler, Bunning Food Allergy Professor, in a press release. "Our results suggest this could contribute to the increasing susceptibility to food allergies."

For the study, the researchers conducted experiments in mice. They exposed germ-free mice (born and raised in sterile conditions to have no resident microorganisms) and mice treated with antibiotics (which significantly reduce gut bacteria) to peanut allergens.

The researchers found that both groups of mice showed strong immunological response by producing higher levels of antibodies against peanut allergens than mice with normal gut bacteria.

They also found that the sensitization to food allergens can be reversed. When the researchers introduced another major group of intestinal bacteria, Bacteroides, they failed to ease sensitization. This indicates that Clostridia possesses a unique, protective ability against food allergens.

Genetic analysis revealed that Clostridia caused innate immune cells to produce high levels of interleukin-22 (IL-22).

Antibiotic-treated mice, which were either given IL-22 or were colonized with Clostridia, showed reduced allergen levels in their blood, compared to control groups. However, the allergen levels significantly increased after the mice were given antibodies that neutralized IL-22. This indicates that Clostridia-induced IL-22 prevents allergens from entering the bloodstream.

"We've identified a bacterial population that protects against food allergen sensitization," Nagler said. "The first step in getting sensitized to a food allergen is for it to get into your blood and be presented to your immune system. The presence of these bacteria regulates that process."

The finding is published in the Journal Proceedings of the National Academy of Sciences.

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