Immunosuppressive activity of a cycloartane triterpene glycoside from Beesia calthaefolia by inhibiting T cell proliferation.

BC-1 is a cycloartane triterpene glycoside isolated from the whole plant of Beesia calthaefolia. Our recent studies proved that BC-1 inhibited proliferation of splenic lymphocyte and phagocytosis of macrophages, and inhibited the increased production of TNF-α and IL-1β. However, it lacks of study about the immunomodulatory effect of BC-1 on purified T lymphocytes. Therefore, in the present study, we evaluated the suppressive potentials of BC-1 on immune responses in vitro. BC-1 markedly suppressed anti-CD3/CD28 mAbs (mAbs) induced murine T lymphocytes proliferation, the expression levels of CD69 and CD25 of CD3 T cells. BC-1 could strongly decrease ratio of CD4/CD8, decrease the Th1/Th2 cytokines production (IL-2, IFN-γ, IL-4, and IL-10) of CD4 T-cells. In addition, we studied signal transduction pathways about T-cell activation on puried murine CD4 T lymphocytes by western-blot assay. The data revealed that BC-1 could inhibit the activation of JNK, ERK and PI3K/AKT signal transduction pathways. These results indicated that BC-1 possesses potential downregulating effect on the immune system and might be developed as an immunosuppressive agent in treatment of CD4 T cell-mediated inflammatory and undesired immune responses.