SWITZERLAND — A Swiss research team published a study on July 6, 2026, demonstrating that genetically engineered immune cells suppressed asthma symptoms in mice when exposed to birch pollen. Yannick D. Muller, an associate professor at Lausanne University Hospital and the University of Lausanne, led the study published in the Journal of Experimental Medicine.

The research involved developing chimeric allergen receptors (CAlleRs) designed to specifically recognize a component of birch tree pollen. These CAlleRs were based on antibodies isolated from a patient with birch allergies and were linked to protein signaling domains that activate regulatory T cells (Tregs).

Tregs are immune cells that can reduce the body's immune responses and prevent excessive inflammation. The effectiveness of Treg-based therapies is typically limited by their lack of specificity. The researchers found that exposure to the birch pollen allergen, when stabilized by noncompetitive antibodies, boosted the suppressive activity of Tregs expressing CAlleRs.

The team injected CAlleR-expressing Tregs into mice previously allergic to birch pollen. These mice showed decreased signs of allergic inflammation, reduced mucus production, and increased lung function when re-exposed to birch pollen. In another part of the study, CAlleR-expressing Tregs were injected into mice that had not been exposed to birch pollen. These mice did not develop asthma symptoms upon subsequent pollen exposure.

"Our study provides proof-of-concept and preclinical evidence that CAlleR Tregs redirected against a birch pollen allergen can downmodulate birch pollen–induced allergic asthma," Muller said. He added, "Future studies should evaluate the persistence and stability of CAlleR Tregs over time and define the optimal modalities for implementing such a therapeutic approach."

The authors suggested that CAlleRs could also be developed to suppress immune responses to other common allergens, such as house dust mites or certain food allergens. The study carries the title "Chimeric allergen receptor regulatory T cells suppress birch pollen allergic airway inflammation," and its associated DOI is 10.1084/jem.20252201. A. Alcaraz-Serna and colleagues were among the study authors.

Why It Matters

Asthma affects over 300 million people globally, with approximately 60% experiencing allergic asthma. Allergen immunotherapy is currently the only treatment that addresses the underlying cause of asthma, but it is not recommended for patients with severe asthma. "This highlights the need for new, safe, and durable treatments for restoring allergen tolerance in severe allergic asthma," Muller said.