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<sup>+</sup> and surface expression of CD203c<sup>bright</sup>, CD63<sup>+</sup>, and CD107a<sup>+</sup> on chemoattractant receptor-homologous molecule expressed on T<inf>H</inf>2 lymphocytes (CRTh2)-positive basophils were measured by means of flow cytometry. Serum IgG<inf>4</inf> 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<sup>+</sup>CRTh2<sup>+</sup> basophils were higher in participants in the SCIT, SLIT, and SLIT-TOL groups (all P <.0001) compared with those in patients in the SAR group. Similarly, there were lower proportions of CRTh2<sup>+</sup> basophils expressing surface CD203c<sup>bright</sup> (all P <.001), CD63 (all P <.001), and CD107a (all P <.01). Rhinitis symptoms were lower in the SCIT, SLIT, and SLIT-TOL groups (P <.001) compared with those in the SAR group. Serum inhibitory activity for IgE-FAB and basophil histamine release were also significantly greater in all immunotherapy groups (P <.05) compared with the SAR group. Conclusion These results support long-term clinical and immunologic tolerance during and after grass pollen immunotherapy. Intracellularly labeled DAO expression by basophils merits further investigation as a surrogate biomarker for monitoring efficacy and tolerance after immunotherapy.
Shamji, M. H., Layhadi, J. A., Scadding, G. W., Cheung, D. K. M., Calderon, M. A., Turka, L. A., … Durham, S. R. (2015). Basophil expression of diamine oxidase: A novel biomarker of allergen immunotherapy response. Journal of Allergy and Clinical Immunology, 135(4), 913-921.e9. https://doi.org/10.1016/j.jaci.2014.09.049