# Modulation of type 2 inflammation during grass pollen-specific sublingual immunotherapy

## TL;DR

This study shows that grass pollen-specific sublingual immunotherapy reduces type 2 immune responses in allergic rhinitis patients, leading to long-term clinical improvement.

## Contribution

The study provides new insights into the immunological mechanisms of sublingual immunotherapy in modulating type 2 inflammation.

## Key findings

- Frequencies of IL-4 and IL-13 producing CD4+ T cells decreased after one year of treatment.
- Clinical improvement was sustained over three years despite stable grass-specific IgE levels.
- IFN-γ producing CD4+ T cells remained stable during the treatment period.

## Abstract

Both ILC2 and Th2 cell subsets play a critical role as functional effector cells in the pathogenesis of allergic diseases. Although allergen-specific immunotherapy is currently the only disease-modifying therapy available for allergic disorders, the immunological mechanisms interfering with type 2 immune response are not yet fully explored.

This study focuses on describing the immunological changes caused by standardized grass pollen-specific sublingual immunotherapy (SLIT) in a cohort of patients with seasonal allergic rhinitis. Patients diagnosed with moderate to severe seasonal allergic rhinitis were enrolled and treated with grass pollen-specific SLIT for a duration of three years. We investigated circulating CD4+ T cells and ILC2 via flow-cytometry, assessing their cytokine expression. Grass-specific IgE levels were assessed.

We observed a decrease of frequencies of IL-4 and IL-13 producing, and CD154-expressing, CD4+ T cells after one year of treatment, while frequencies of IFN-γ producing CD4+ T remained stable. We also observed significant and long-term clinical improvement induced by SLIT, although grass-specific IgE levels remained relatively stable over time.

These exploratory findings collectively suggest early modulation of the type 2 immune response with sustained clinical response regardless of persistent allergic sensitization in patients undergoing grass pollen-specific SLIT for allergic rhinitis.