Microbiome And Allergies
Scientists are targeting imbalances in intestinal bacteria, known as the microbiome, to find a new way to fight food allergies. According to Cathryn Nagler, an immunologist at the University of Chicago there is hope that gut bacteria might be a way to reset the immune system and help people overcome the risk for severe food allergic reactions. (1)
MICROBIOME AND ALLERGIES IN MICE
Nagler and team reported they supplied gut microbes from healthy, non-allergic babies and prevented severe allergic responses in allergy-prone mice. “The data are sound, and they are very encouraging,” says pediatric allergist Jaclyn Bjelac of the Cleveland Clinic. (1)
Back in 2004, Nagler and her coworkers reported peanuts provoked anaphylaxis only in mice with a mutated TLR4 receptor, which sits in the membranes of immune cells. Its job is to recognize microbes. The reaction was not found in genetically related strains with a normal TLR4. This different reaction, however, was eliminated when they wiped out populations of gut bacteria with antibiotics. In this case, even normal mice were susceptible to food allergies. This implied that bacteria are at the root of the protection. Nagler’s lab continues to pursue which bacteria might be helpful in regulating allergic responses. (1)
SPECIFIC BACTERIA IN MICROBIOME AND ALLERGIES
Two major bacteria groups in the gut, Clostridia and Bacteroides, have been the focus of the study on mice bred in a germ-free environment. Because the environment is germ-free, the mice don’t have any microbiome. Clostridia, but not Bacteroides, prevented food-allergic responses once placed in the guts of the “clean” mice. (1)
The reason for this could be related to the mice colonized with Clostridia bacteria having more regulatory T cells, which reduce immune responses. As well, the Clostridia mice produced more of IL-22, a molecule that strengthens intestinal lining. This led to the theory that when there are missing protective microbes it weakens the gut barrier so food proteins can seep into the bloodstream which in turn could trigger allergic responses. (1)
COMMONALITY FOR MICROBIOME AND ALLERGIES
These findings work along with an observation that the typical food allergies to proteins in foods such as peanuts, eggs, milk, etc. have few biochemical things in common. However, the one thing that they all share is that they can remain intact in the digestive tract, where food is normally broken down into small pieces to be absorbed as nutrients. “That seems to be what makes peanut the champion—its ability to resist degradation in the gut,” explains Nagler. (1)
Further supporting the gut bacteria and food allergies link, this finding suggests the microbiome’s impact comes early in life. By analyzing healthy baby feces and those with egg or milk allergies, the team showed the communities of gut bacteria in allergic and nonallergic infants were different. (1)
EARLY-IN-LIFE TIES TO MICROBIOME AND ALLERGIES
Another study suggesting that allergy protective microbes only act early in life, tested children with milk allergies from infancy to age 8. The results showed that from 2 to 6 months certain bacteria, including Clostridia, were enriched in stool samples. These infants outgrew their allergy, while this was not seen in older babies. (1)
“All of this points to the concept of a window of opportunity in terms of prevention,” says the leader of this particular study, pediatric allergist Supinda Bunyavanich, of the Icahn School of Medicine at Mount Sinai in New York City. (1)
The microbiome is important for preventing food allergies and inducing tolerance, according to Carina Venter, a research dietician at the University of Colorado in Denver. However, she also points out “how that microbiome should look in terms of diversity and in terms of specific strains, we just don’t know.” (1)
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