Nicole Zhao ’20

A food allergy is an immune system reaction that occurs when exposed to a certain food (1). Symptoms resulting from an allergic reaction include digestive problems, hives, swollen airways and even anaphylaxis (1). Anaphylaxis is a serious, life-threatening allergic reaction and encompasses a variety of symptoms with high severity (2). During an allergic reaction, the immune system recognizes that a specific food as a foreign substance and produces antibodies against it (2). Currently, more than 32 million people in the United States suffer from food allergies and there is no cure for this condition (3). Although there are many allergy therapies under study, food allergies are mainly managed by avoiding the foods that cause the allergic reaction and learning how to treat its symptoms (3). 

Previous research has suggested that the gut microbiota, the complex ecosystem of microorganisms that live in the gut, plays a fundamental role food sensitivity (4). Moreover, it was previously found that a reduced bacterial diversity acquired within the first years of life is characteristic of children with food allergies (4). In a new study led by Dr. Abdel-Gadir using patient samples from Boston Children’s Hospital and Brigham and Women’s Hospital, it was found that while the diversity of gut microbiota in infants with food allergies evolved over time, it still failed to protect against food allergies (5). However, when species of bacteria from the Clostridiales or Bacteroidales order were  reintroduced in the guts of mice models with food allergies, their food allergies were actually suppressed (5). 

The underlying mechanism for the suppression of food allergies by this form of bacteriotherapy is the activation of a MyD88-dependent microbial-sensing pathway in developing regulatory T (Treg) cells (5). Treg cells are in charge of suppressing potentially deleterious activities of T helper cells, which are responsible for immunity against pathogens and cancer (6). The young Treg cells whose microbial sensing pathway is activated then develop into disease-suppressing ROR-γt+ Treg cells which are crucial in suppressing the overactivity of the immune system when a certain food is present (5). This finding is further bolstered by the finding that the ROR-γt+ Treg cells are deficient in children with food allergies while present is infants without food allergies (5). 

This study is important in that it identified a connection between an evolving gut microbiota and food sensitivity in children with food allergies. Moreover, this study uses this observation to experiment with a potential microbial therapy for individuals suffering from food allergies. The therapy’s success is also underscored by the identified mechanism in developing disease-suppressing ROR-γt+ Treg cells which are necessary in preventing food allergies.

References:

1. Food Allergy. Mayo Clinic, (2017). 
2. Anaphylaxis. Mayo Clinic, (2018). 
3. Facts and Statistics. Food Allergy Research & Education. 
4. M. B. Azad, et al., Infant gut microbiota and food sensitization: associations in the first year of life. Clinical & Experimental Allergy 45, 632–643 (2015). doi: 10.1111/cea.12487.
5. A. Abdel-Gadir, et al., Microbiota therapy acts via a regulatory T cell MyD88/RORγt pathway to suppress food allergy. Nature Medicine (2019). doi: 10.1038/s41591-019-0461-z.  
6. A. Corthay. How do regulatory T cells work? Scandinavian Journal of Immunology 70, 326-336 (2009). doi: 10.1111/j.1365-3083.2009.02308.x.
7. Image retrieved from: https://www.gettyimages.com/detail/photo/gut-bacteria-microbiome-3d-illustration-royalty-free-image/586183298