Essential Oil of Citrus Sudachi Suppresses T Cell Activation Both in Vitro and in Vivo.

The essential oil of Citrus sudachi (sudachi oil) is extracted from the peel of sudachi, a citrus plant. We investigated the effect of sudachi oil on immune function in both in vitro antigen (Ag) induced lymphocyte activation and in vivo Ag-specific immune response. In the in vitro study, the proliferative activity of splenocytes upon Ag-specific and non-specific stimulation was suppressed by treatment with sudachi oil in a dose-dependent manner. In addition, the expression level of Ag-presentation-related molecules and their Ag-presenting function on dendritic cells were suppressed by sudachi oil. To examine how sudachi oil regulates an Ag-specific immune response in vivo, mice were immunized with ovalbumin and the immune response of the mice was investigated. Ag-specific proliferation response of splenocytes from mice treated with sudachi essential oil was significantly suppressed. The results indicate that sudachi oil suppresses T cell and dendritic cell functions in vitro and Ag-specific T cell induction in vivo.