Mesenchymal stem cells and mesenchymal stem cell-derived extracellular vesicles: Potential roles in rheumatic diseases

Figure 1 Immunomodulatory effects of mesenchymal stem cells. The inflammatory microenvironment stimulates mesenchymal stem cells (MSCs), leading to the acquisition or boost of their immunosuppressive property, then activated MSCs promote the conversion of pro-inflammatory macrophages (M1) into an anti-inflammatory phenotype (M2) and activation of Tregs as well as T helper 2 (Th2) cells, while inhibit the functions of Th1 cells, Th17 cells, B cells, dendritic cells, and natural killer cells. Actually, MSCs can also inhibit the amplification and differentiation of T cells indirectly via regulatory T cells. NK cell: Natural killer cell; DC: Dendritic cell; Th cell: T helper cell; Treg: Regulatory T cell.