Cellular Mechanism and Key Insights in Allergen Immunotherapy for Allergic Rhinitis

Allergic rhinitis (AR) arises from immune responses mediated by immunoglobulin E (IgE) to inhaled allergens, representing one of the most prevalent chronic conditions worldwide. Although AR may not be a serious ailment, it holds clinical relevance as it underpins numerous complications, serves as a major risk factor for suboptimal asthma control, and adversely affects quality of life and productivity in both work and school environments. Prevention and treatment strategies for AR encompass various approaches, including allergen avoidance, pharmacotherapy, allergen-specific immunotherapy (AIT), and patient education. Among the treatments for AR, AIT stands out as the only curative intervention. It offers a targeted and long-term solution by modifying the underlying immune response, providing lasting relief for individuals with AR. AIT, which targets individual allergens, is garnering increasing attention due to recent evidence from numerous randomized controlled trials and long-term real-life studies that attest to its effectiveness. By actively altering the immune response, AIT modifies the natural course of allergy, offering benefits that extend beyond the immediate symptom relief. In this updated review, we provide new insights into the roles of diverse immune cells involved in AIT for the treatment of AR. AIT inhibits FcεRⅠactivity, enhances epithelial function, reduces pro-inflammatory ILC2s while promoting immunoregulatory IL-10⁺ILC2s, augments regulatory DCreg subsets, and drives a shift from Th2 to Th1 immune responses. The objective of this review is to explore the fundamental principles and effectiveness of immunotherapy in the management of AR, as well as to showcase the latest developments in this area of research.