Teucrium montanum extract drives effector and memory differentiation of CD8+ T cells

Introduction: Teucrium montanum has been traditionally used for immune system strengthening. However, T cell-related mechanisms of the Teucrium species remain poorly understood. In this study, we investigated the impact of T. montanum extracts and their fractions in stimulating proliferation and, more importantly, in differentiation into effectors and memory T cells. Methods: The dried, aerial part of T. montanum was extracted in four different solvents: petroleum ether, dichloromethane, ethyl acetate, and methanol. A total of 67 fractions were subsequently collected from the dichloromethane extract in a stepwise gradient system of petroleum ether/acetone followed by methanol. An Alamar Blue assay and flow cytometry were employed to characterize the influence on T cell response by the plant extracts or fractions. Results: The dichloromethane extract showed promotive effects on the proliferation and activation of total lymphocytes, and this was more prominent in CD8+ T cells. Among the 67 fractions from the dichloromethane extract, nine were found to demonstrate pro-proliferative activity. Further testing revealed that three methanolic or acetone subfractions out of the nine fractions were able to either promote effector/effector memory differentiation of primed CD8+ T cells or skew the T cells into a central memor y phenotype. Conclusion: Our results suggest that T. montanum can drive proliferation of T cells and regulate the development of effector and memory populations, apparently corroborating the reported immunological benefits of T. montanum.