Biomarkers and immune cells in allergen-specific immunotherapy

BACKGROUND: Allergen-specific immunotherapy (AIT) is the only intervention capable of modifying the natural course of allergic diseases by inducing long-term immune tolerance. Its clinical efficacy depends on complex regulations of humoral and cellular immunity, yet objective assessment remains hindered by the absence of standardized biomarkers. SUMMARY: This review summarizes recent advances in the immunological mechanisms of AIT and highlights emerging biomarkers-including allergen-specific immunoglobulin G4, regulatory T and B cells, and innate lymphoid cells-that may provide objective measures of efficacy and support individualized treatment strategies. KEY MESSAGES: (1) AIT uniquely modifies the natural history of allergic diseases; (2) current evaluation relies on subjective measures, highlighting the urgent need for standardized and clinically applicable biomarkers; (3) molecular markers and immune cell subsets offer promising tools for bridging mechanistic insights with clinical endpoints, supporting real-time monitoring and precision-guided optimization of AIT.