Decreased Basophil Activation against House Dust Mite after Japanese Cedar Pollen Subcutaneous Immunotherapy: A Retrospective Study

Background: Allergen-specific immunotherapy (AIT), an established treatment for allergic diseases, prevents the development of other allergic manifestations. Although the mechanisms remain unclear, AIT has been shown to reduce basophil activation (BA) against nontarget allergens. Objectives: The aim of this study was to assess immunological changes in Dermatophagoides farinae (Der f) after Japanese cedar pollen (JCP)-based subcutaneous immunotherapy (SCIT) monotherapy. Method: The data of 16 patients (age: 6-37 years) with JCP-induced allergic rhinitis who were sensitive to Der f (serum Der f-specific immunoglobulin E [IgE] level >0.34 kU_A/L) and received JCP-based SCIT for 5 years were reviewed retrospectively. BA by Der f and JCP extracts and serum-specific IgE and immunoglobulin G4 (IgG4) levels against these allergens were evaluated before and after completing 5 years of JCP-based SCIT monotherapy. Results: The areas under the dose-response curves of BA by Der f and JCP extracts were significantly reduced (p = 0.02 and p = 0.002, respectively). JCP-specific IgE levels decreased and JCP-specific IgG4 levels increased significantly (p < 0.001 for both), whereas Der f-specific IgE and IgG4 levels did not change significantly. Conclusions: JCP-based SCIT monotherapy reduced Der f-specific BA. These findings suggest that JCP-based SCIT has the potential to modulate immune response toward nontarget allergens.