D2.155 - Factors associated with higher serum IgG4 response in children treated with allergen immunotherapy

Allergen immunotherapy (AIT) is a well-established treatment for allergic rhinitis (AR) and asthma. AIT can induce tolerance to the allergens, decrease in TH2 inflammation, and promote regulatory T-cells. It also increases allergen-specific IgG4 antibodies which block allergen-specific IgE from binding to allergens. We investigated immunological changes during AIT and identify factors associated with high allergen-specific IgG4 levels after one year of treatment. 

We included children diagnosed with AR or asthma. These children had elevated allergen-specific IgE levels to house dust mite (HDM) or birch pollen and were treated with AIT for at least two years. Blood tests were performed before and annually after initiation of AIT. We measured serum total IgE, allergen-specific IgE, and allergen-specific IgG4 levels using ImmunoCAP. We investigated characteristics of children with high IgG4 levels (upper 15%) compared to those with low IgG4 levels (lower 15%) at 1 year after AIT. 

Total of 97 children were enrolled (mean age 10±3 years). Boys were 61 (63%). Total of 71 children were treated with HDM and 26 children were treated with birch pollen. Changes of allergen-specific IgE levels decreased significantly in HDM group, but not in birch pollen group. In both group, allergen-specific IgG4 levels increased significantly and allergen-specific IgE/IgG4 ratio showed a significant decline. Children who started AIT at a younger age, particularly below 10 years old, showed significantly higher IgG4 levels. Children with higher initial allergen-specific IgE levels (above 60 kU/L) demonstrated greater IgG4 increases. 

AIT is effective in inducing immunological changes, including increased allergen-specific IgG4 levels and reduced allergen-specific IgE/IgG4 in children. Starting AIT early and targeting children with higher allergen-specific IgE levels may lead to better outcomes.