The effect of silymarin on the proliferating of the activated human T cells in vitro

Background: The widespread use of herbal medicines, because of their protective effects on various organs, has been shown in many studies. Silymarin is a flavonolignan complex isolated from the milk thistle (Silybum marianum L. Gaertn), has been clinically used for its anti-inflammatory and hepatoprotective effects. Recently, immunomodulating effects of this plant have considered by the researchers. This study aimed to investigate the effect of silymarin and dimethyl sulfoxide (DMSO) on the human T lymphocyte proliferation under the cell culture conditions. Methods: Peripheral blood mononuclear cells (PBMCs) from the healthy individuals were activated with Con A (10 μg/ml) and treated with silymarin at different concentrations (0.001, 0.01, 0.1, 1, 10, 100 and 200 μM). Then, cells were incubated for five days at 37° C with 5% CO₂ for proliferation assay using the carboxyfluorescein succinimidyl ester (CFSE) dye and for viability analysis using flow cytometry. We analyzed the data using the Graph pad prism (version 6) software. Findings: Silymarin had the ability to inhibit the T cell proliferation in vitro. Moreover, 100 μM and 200 μM of silymarin had more inhibitory effect on T cells (P < 0.001). Conclusion: We conclude that silymarin exerts immunosuppression effects, and it could be used in therapeutic situations with fewer side effects compared with the other immunosuppressive drugs.