Basophil expression of diamine oxidase: A novel biomarker of allergen immunotherapy response

Abstract

Background Immunotherapy inhibits basophil histamine release, but the assay is cumbersome, and no one has studied the effects of immunotherapy withdrawal. Objective Intracellular fluorochrome-labeled diamine oxidase (DAO) was used as a novel functional readout of basophil histamine release after immunotherapy. Results were compared with conventional basophil surface expression of activation markers. Methods Subcutaneous immunotherapy (SCIT)-treated patients (n = 14), sublingual immunotherapy (SLIT)-treated patients (n = 12), participants who completed 3 years of treatment with grass pollen sublingual immunotherapy (the SLIT-TOL group; n = 6), patients with untreated seasonal allergic rhinitis (SAR; n = 24), and nonatopic control subjects (n = 12) were studied. Intracellularly labeled DAO+ and surface expression of CD203cbright, CD63+, and CD107a+ on chemoattractant receptor-homologous molecule expressed on TH2 lymphocytes (CRTh2)-positive basophils were measured by means of flow cytometry. Serum IgG4 levels and serum inhibitory activity for IgE-allergen complex binding to B cells (IgE-FAB) and basophil histamine release were also determined. Results Proportions of allergen-stimulated DAO+CRTh2+ basophils were higher in participants in the SCIT, SLIT, and SLIT-TOL groups (all P