Epigenetic Modification of Enhancer of Zeste Homolog 2 Modulates the Activation of Dendritic Cells in Allergen Immunotherapy

Background: Allergen immunotherapy (AIT) is the only etiological and potentially curative therapy for allergic rhinitis (AR). Objectives: We sought to investigate the role of epigenetic regulator enhancer of zeste homolog 2 (EZH2) in the activation of dendritic cells (DCs) in AIT. Method: In this study, EZH2 expression in circulating myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) were evaluated using flow cytometry. Clinical information from 56 AR patients receiving AIT was collected, including 30 subjects with subcutaneous immunotherapy (SCIT) and 26 subjects with sublingual immunotherapy (SLIT). In vitro, the effect of EZH2 inhibitor, 3 Deazaneplanocin A (DZNep), on the phenotypic and functional activation of monocyte-derived DCs (moDCs) was evaluated. Results: EZH2 expression in circulating mDCs and pDCs were both negatively correlated to treatment time of AIT (r = -0.39, p = 0.003 and r = -0.47, p = 0.0002, respectively). Furthermore, there was a higher correlation between EZH2 expression and AIT treatment time in the SCIT group compared to that of the SLIT group in mDCs (r = -0.42, p = 0.02 vs. r = -0.23, p = 0.26)and pDCs (r = -0.52, p = 0.003 vs. r = -0.33, p = 0.10). In vitro, the co-stimulatory molecules on moDCs, such as CD80, CD86, and CD83, were significantly inhibited by DZNep in a dose-dependent manner. The -DC-driven T-cell proliferation was suppressed by DZNep (MD = 22.88, 95% CI 7.809-37.96, p < 0.05). Conclusions: Our study shows that EZH2, which is required in the activation of DCs, mediates the epigenetic modification in AIT and stresses the importance of patient adherence during AIT.