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Introduction
Macrophages are important phagocytic and antigen-presenting cells in the body and they serve an important role in handling external pathogenic microorganisms and endogenous danger signals. Macrophages are widely distributed in various tissues and organs and are important in maintaining homeostasis, body defense, regulating inflammation and promoting wound healing (1).
As important immune cells in human body, macrophages serve an important role in antigen presentation and inflammatory response. A recent study demonstrated that macrophages are a group of heterogeneous and flexible cells with diverse and varied immune functions, and they can polarize into different phenotypes in different microenvironments or under different stimuli, playing different roles in inflammatory response of tissues (2). Depending on the activation and immune functions, they can be divided into the classically activated type (M1 type) and the alternatively activated type (M2 type). M1 type macrophages are activated by T helper (h)1 cytokines of helper T lymphocytes, such as interferon (IFN), tumor necrosis factor (TNF) and bacterial lipopolysaccharides (LPS), and the activated cells can induce the expression of pro-inflammatory cytokines, such as interleukin (IL)-6, TNF-α and IL-1β, resist pathogen invasion, and participate in the inflammatory response, but they can also cause body injury, which is manifested as high antigen-presenting ability (3). M2 type macrophages are activated by Th2 cytokines and, following activation, they can induce high expression of anti-inflammatory cytokines including IL-10, transforming growth factor-β and arginase, and low expression of pro-inflammatory cytokines, thereby inhibiting the inflammatory response, protecting surrounding tissues from the harm caused by immune response and promoting repair of tissue injuries (4). Therefore, a deep study into the internal mechanism of macrophages polarity differentiation will be of great importance for a better understanding occurrence, development and treatment of various immune-related diseases.
The suppressor of cytokine signaling (SOCS) family is a collection of negative regulatory factors that are generated by cells and can block cytokine signaling in feedback (5). As one important member of the family, SOCS1 is involved in various cytokine signal transductions and the differentiation of immune cells, and serves an important role in innate and adaptive immune response. As an important determinant for the activity and function of differentiated macrophages, SOCS1 is not only a feedback inhibitor of inflammation, but is also an important molecular switch that...