These Findings Are Nothing to Sneeze At

Why do allergies happen to certain people and not others? The answer may come down to a set of "memory cells" within the immune system.


Allergies occur when the body’s immune system reacts to a foreign substance, such as pollen, dust, or certain types of food. Despite being innocuous to most individuals, these substances trigger an abnormal immune response in allergic individuals, leading to the production of antibodies specifically targeted against them, known as allergens.

Allergies can vary in severity ranging from minor irritation to anaphylaxis. During anaphylaxis the immune system releases a flood of chemicals that can cause the body to go into shock by causing sudden drops in blood pressure, narrowing of airways and vomiting. If not treated right away, anaphylaxis can be fatal. 

Despite the widespread prevalence of allergies globally, the process through which allergies develop and persist throughout a person’s life remains largely mysterious.

To tackle some of these obstacles, Dr. Josh Koenig — an assistant professor in the Department of Medicine at McMaster University — co-led by pharmaceutical company ALK in Denmark, has discovered a subset of immune cells called the type 2 Memory B Cells (MBC2). These cells seem to be disproportionately present in allergic people, and almost non-existent in non-allergic people. Their findings were published in Science Translational Medicine.

B cells are the subset of immune cells responsible for producing antibodies against pathogens during an immune response. In the case of allergies, a specific subset of antibodies, IgE antibodies, are produced.

After an infection, a population of memory B cells develops, enabling the immune system to recognize and respond more effectively to future encounters with the same pathogen. In the case of allergies, B cells produce antibodies against substances perceived as threats, even though they are harmless. This includes dust, pollen, and certain foods.

The MBCs identified in this study express markers that are associated with type 2 immunity. Type 2 immune responses are typically mounted against helminths (i.e., parasitic worms) and other parasites, and are also involved in allergies.

The researchers delved into samples from clinical trials to sequence the IgE producing B cells. They found a direct connection between type 2 memory B cells and IgE, which is the type of antibody triggering an allergic reaction. Specifically, these cells were enriched in adults with peanut, birch, or house dust mite allergy compared to non-allergic adults. These cells also produced allergen-specific IgE antibodies. The study also showed the emergence of a similar population of allergen-specific MBC2s in mouse models of allergy. 

The discovery of B cells holding IgE memory opens up new possibilities for therapeutic interventions. Targeting and eliminating these cells from allergic individuals could potentially mitigate allergic reactions. 

Allergies are complex immune responses that can range from mild inconveniences to life-threatening emergencies. Understanding the role of memory B cells, particularly MBC2 cells, offers hope for developing more targeted and effective treatments for allergies.

With further research and development, we may one day be able to provide relief to millions of individuals who suffer from allergies worldwide.

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Sumayya Abdul Qadir is a PhD student in the Department of Molecular Genetics at the University of Toronto where she also earned her Bsc in Molecular Genetics and Immunology. Sumayya’s passion for science communication is driven by the desire to bridge the gap between complex scientific concepts and the general public, fostering understanding, curiosity, and engagement with the wonders of the scientific world.