Silymarin impacts on immune system as an immunomodulator: One key for many locks.
Silymarin is a flavonoid complex extracted from the Silybum marianum plant. It acts as a strong antioxidant and free radical scavenger by different mechanisms. But in addition to antioxidant effects, silymarin/silybin reveals immunomodulatory affects with both immunostimulatory and immunosuppression activities. Different studies have shown that silymarin has the anti-inflammatory effect through the suppression of NF-κB signaling pathway and TNF-α activation. It also has different immunomodulatory activities in a dose and time-dependent manner. As an immunomodulator agent, silymarin inhibits T-lymphocyte function at low doses while stimulates inflammatory processes at high doses. Studies have shown that silymarin has attenuated autoimmune, allergic, preeclampsia, cancer, and immune-mediated liver diseases and also has suppressed oxidative and nitrosative immunotoxicity. Silymarin also has indicated dual effects on proliferation and apoptosis of different cells. In conclusion, based on the current review, silymarin has a broad spectrum of immunomodulatory functions under different conditions. Recognizing the exact mechanisms of silymarin on cellular and molecular pathways would be very valuable for treatment of immune-mediated diseases. Also further studies are needed to assess the utility of silymarin in protection against autoimmune, cancer, allergic and other diseases in human subjects.