Sublingual Immunotherapy Induces Regulatory Function of IL-10-Expressing CD4+CD25+Foxp3+ T Cells of Cervical Lymph Nodes in Murine Allergic Rhinitis Model

Sublingual immunotherapy (SLIT) has been considered to be a painless and efficacious therapeutic treatment of allergic rhinitis which is known as type I allergy of nasal mucosa. Nevertheless, its mechanisms need to be further investigated. In this study, we constructed an effective murine model of sublingual immunotherapy in allergic rhinitis, in which mice were sublingually administered with ovalbumin (OVA) followed by intraperitoneal sensitization and nasal challenge of OVA. Sublingually treated mice showed significantly decreased specific IgE responses as well as suppressed Th2 immune responses. Sublingual administration of OVA did not alter the frequency of CD4(+)CD25(+) regulatory T cells (Tregs), but led to upregulation of Foxp3- and IL-10-specific mRNAs in the Tregs of cervical lymph nodes (CLN), which strongly suppressed Th2 cytokine production from CD4(+)CD25(-) effector T cells in vitro. Furthermore, sublingual administration of plasmids encoding the lymphoid chemokines CCL19 and CCL21-Ser DNA together with OVA suppressed allergic responses. These results suggest that IL-10-expressing CD4(+)CD25(+)Foxp3(+) Tregs in CLN are involved in the suppression of allergic responses and that CCL19/CCL21 may contribute to it in mice that received SLIT.