Juzentaihoto Exerts Anti-Allergic Effects by Inhibiting Effector T-Cell Activation and Inducing and/or Activating Regulatory T Cells in a Murine Model of Contact Hypersensitivity

Background: Juzentaihoto (JTT) is a Kampo prescription that has been used clinically for treating skin diseases such as atopic dermatitis in Japan. We have previously studied the anti-allergic effects of JTT on 2,4,6-trinitrochlorobenzene (TNCB)-induced contact hypersensitivity (CHS) in mice and demonstrated that it significantly suppresses ear swelling in a dose-dependent manner. However, the mechanism underlying the anti-allergic actions of JTT is obscure. Methods: We investigated the mechanism underlying the anti-allergic effects of JTT using a TNCB-induced murine CHS model and adoptive cell transfer experiments. Results: We showed that the anti-allergic effects of JTT are due to inhibition of effector T-cell activation and induction and/or activation of regulatory T cells. Furthermore, ex vivo experiments confirmed the effect of JTT on the activation of effector T cells and regulatory T cells, as interferon-gamma production decreased, whereas interleukin (IL)-10 production increased, in the cultured lymphocytes obtained from 5% TNCB-sensitized mice treated with anti-CD3 epsilon and anti-CD28 monoclonal antibodies. Flow cytometry showed that the CD4(+)CD25(+)Foxp3(+), CD4(+)CD25(+)Foxp3(-), and CD8(+)CD122(+) cell population increased after oral administration of JTT. Finally, the anti-allergic effect of JTT by inducing and/or activating regulatory T cells (Tregs) was confirmed to be mediated by IL-10 through in vivo neutralization experiments with anti-IL-10 monoclonal antibodies. Conclusion: We suggested that JTT exerts anti-allergic effects by regulating the activation of effector T cells and Tregs involved in murine CHS model.