Fig. 1

The role of macrophages in IIMs. When tissue is damaged, inflammatory monocytes are recruited from the circulation and are converted into macrophages during migration. At the same time, resident tissue macrophages proliferate while recruiting peripheral blood immune cells, which primarily constitute the first wave of immune cell influx. Activated macrophages tend to exhibit a proinflammatory phenotype at an early stage. They can exert direct killing effects by producing ROS, NSs and proteases. In addition, macrophages secrete a variety of inflammatory mediators to drive autoimmune inflammation, and cytokines secreted by macrophages can induce the differentiation and expansion of Th1 and Th17 cells and promote the development of inflammatory responses. On the other hand, the phagocytosis of apoptotic cells by macrophages can be enhanced by Tregs. All these factors contribute to the progression of inflammation. ROS, reactive oxygen species; Treg, regulatory T cells; NS, nitrogen species; Th1 and Th17 cells, T helper cells that express IFN-γ and IL-17; IL-6, interleukin-6; IL-10, interleukin-10; IL-13, interleukin-13; IL-12, interleukin-12; IL-23, interleukin-23; TNF-α, tumor necrosis factor-α