TGF-β as a promising option in the treatment of multiple sclerosis

Transforming growth factor-β (TGF-β) is a potent regulatory cytokine with diverse effects on hemopoietic cells. The pivotal function of TGF-β in the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. Among T cells, CD4+CD25+FOXP3+ T regs contain the main source of TGF-β that suppresses immune responses in inflammatory sites. Defects in TGF-β1 expression or its signaling in T cells correlate with the onset of several autoimmune diseases. Thus, understanding the function and regulation of TGF-β during immune responses offers therapeutic promise for the control of autoimmune diseases such as multiple sclerosis. However, the main mechanism by which TGF-β exerts its protective effects on the experimental model of multiple sclerosis remains to be elucidated. Paradoxically, TGF-β1 also acts as a pro-inflammatory cytokine and induces interleukin 17-producing pathogenic T helper cells (Th IL-17 cells) synergistically during an inflammatory response in which interleukin 6 is produced. In this review, we will describe the regulatory and therapeutic effects of TGF-β in multiple sclerosis.