Comparing in-vitro effects of two immunosuppressive drugs on the expression of Foxp3 from Naïve CD4+ T Cells

Background: Many studies showed that regulatory T cells (Tregs) have immunosuppressive effects on immune responses in transplantation and autoimmune disease. Silymarin (isolated from milk thistle or silybum marianum plant) is a flavolignan complex with anti-inflammatory, hepatoprotective, antioxidant and immunomodulatory activities. Previous studies in our group revealed inhibition effect of silymarin on mammalian target of rapamycin (mTOR) activity in activated T cells. Among immunosuppressive drugs, rapamycin can inhibit mTOR, results in Foxp3 expression, Tregs expansion and conventional T cells inhibition. In this study, the effect of silymarin on in-vitro generation of CD4+Foxp3+ cells, in comparison with rapamycin, was evaluated. Methods: Naïve CD4+ T cells were separated from healthy individuals’ peripheral blood mononuclear cells (PBMCs) and activated with monoclonal antibody anti-CD3 and anti-CD28 for 18 hours in Roswell Park Memorial Institute (RPMI) complete medium. Then, incubation was continued with adding Interlukin-2 (IL-2) and silymarin or its control, dimethyl sulfoxide (DMSO), or cultured in present or absent of rapamycin for 3 days. Cells were harvested and stained with anti-CD4 and anti- FoxP3 antibodies for flow cytometry. Findings: Silymarin increased CD4+Foxp3+ T cells compared with its control, DMSO, and with rapamycin after three days of culture of naïve T cells (P <0.05); while, rapamycin compared to its control (RPMI medium) did not increased CD4+Foxp3+ T cells during three days culture (P > 0.05). Conclusion: Given the importance of replacement less harmful medicine and Tregs role in regulating immune system, silymarin, as aTreg generation drug, can be used in the treatment of autoimmune diseases and even in organ transplantation.