Ogonto, a traditional Japanese herbal medicine, attenuates food allergy symptoms in mice through the induction of regulatory T cells.

Despite the rising prevalence of food allergies (FAs) in recent decades, existing therapeutic drugs remain inadequate. Therefore, the development of novel therapeutic strategies for FAs is urgently needed. Baicalein, a flavonoid from Scutellariae baicalensis, has been reported to ameliorate ovalbumin (OVA)-induced FA responses by inducing regulatory T cells (Tregs) in a mouse model. Here, we examined the effects of five traditional Japanese herbal medicines (Kampo medicines) containing Scutellariae radix on Treg induction and FA responses. All five Kampo medicines significantly enhanced the transcriptional activity of Foxp3, a master regulator of Tregs, in a recombinant human Jurkat cell line transfected with a Foxp3-luciferase reporter. Among them, Ogonto exerted the strongest effect. In addition, Ogonto significantly increased Foxp3 gene expression in Jurkat T cells and upregulated the expression of Ten-eleven translocation 2 (TET2) and TET3, demethylating enzymes that contribute to the stable expression of Foxp3. In our HPLC analysis, the Ogonto preparation used in this study was found to contain baicalin, the glycosylated form of baicalein. We next used an OVA-induced FA mouse model to evaluate the effects of Ogonto administration on allergic symptoms and the proportion of Tregs in the mesenteric lymph nodes (mLNs). Ogonto ameliorated OVA-induced diarrhea and rectal hypothermia and reduced OVA-specific immunoglobulin E levels. Furthermore, Ogonto increased the proportion of CD4⁺Foxp3⁺ Tregs in the mLNs of FA mice. These results suggest that Ogonto suppresses the development of FA by increasing Tregs.