Study sheds light on how the immune system “remembers” food allergens

An AllerGen-supported research team at McMaster University is studying why the body’s immune system responds inappropriately to certain foods and why some food allergies are lifelong.

A food allergy is an abnormal immune response to a food. The immune system mistakenly identifies a food as harmful and produces an antibody called immunoglobulin (Ig) E that binds to cells in tissues (mast cells) and in blood (basophils) through a specific receptor. The next time the food is consumed, the allergen (peanut, for example) binds to the IgE and triggers mast cells and basophils to degranulate, releasing molecules such as histamine that cause the allergic reaction.

In their new paper published in the Journal of Allergy and Clinical Immunology, “The IgE Memory Reservoir in Food Allergy”, Drs Manel Jordana, Susan Waserman and Rodrigo Jiménez-Saiz, and PhD students Kelly Bruton and Joshua Koenig, shed light on how the immune system “remembers” food allergens.

“Previous research proposed that upon re-encountering a food allergen, memory IgE cells become activated and replenish the cells that produce IgE antibodies, which ultimately triggers the allergic reaction,” says Dr. Jiménez-Saiz, a Research Associate at McMaster University and the paper’s first author. “However, no one has been able to decipher how the IgE memory works.”

“Recent research suggests that IgG1 memory B cell subsets are the true reservoir of allergen-specific memory, which represents a considerable shift from previous thinking,” adds Dr. Jordana, an AllerGen investigator and a Professor of Pathology and Molecular Medicine at McMaster.

Evidence from mouse and human studies suggests that IgG1 memory B cells survive in the blood and tissues for long periods of time, and that when re-exposed to a food allergen, they evolve into IgE-producing cells under the influence of signalling proteins called interleukin (IL)-4 and IL-13.

“This improved understanding of how immune cells hold their memory provides us with new potential therapeutic targets for allergic diseases,” notes Dr. Jordana. “For example, treatments that block IL-4 and IL-13 signaling may effectively alleviate food allergy, atopic dermatitis, allergic asthma and allergic rhinitis, and could have a tremendous impact on the quality of life of patients.”