Figure 2.

The mechanism of inflammatory reaction and oxidative stress reaction of intestinal flora

In inflammatory reactions, symbiotic microorganisms can regulate the adaptive immune system in various ways. Symbiotic microorganisms produce adaptive immune responses by stimulating the differentiation of Th17 cells and Treg cells, among which Treg cells exert immunosuppressive function on various immune cells through IL-10 and TGF-β. Th17 cells acquire pathogenic inflammatory phenotype with IL-23 and SAP, and they promote the release of IL-17. In the oxidative stress reaction, inflammatory cells, including neutrophils, macrophages, and lymphocytes, produce a large number of ROS and RNS under the stimulation of inflammation, which leads to DNA damage. Anaerobic bacteria activated TLR2/TLR4 on intestinal epithelial cells (IECs) and increased the level of ROS in cells. E. coli and ETBF also stimulate ROS production and cause DNA damage. Inflammation and oxidative stress promote each other, which further leads to the occurrence of CRC.