Conclusion
Gut microbes are indispensable in the gut, and their metabolic roles have been widely studied using metabolomics and bacterial profiling. BAs are metabolized into various configurations by bacteria in the gut and serve as signaling molecules to regulate immunocytes such as Th17 cells and Treg cells in the intestine, thereby regulating intestinal immune balance. The intricate network of relationships among the gut flora, BAs, immunocytes, and cytokines is closely related to multiple diseases throughout the body. Therefore, related research will be conducive to the development of drugs for treating multiple diseases. Research on the mechanism of the activation effect of TGR5 and FXR in macrophages, DC, NKT cells, MDSC, B cells, and intestinal epithelial cells contributes to the development of molecular-targeted drugs. At present, these studies have mainly focused on liver diseases and ischemia-reperfusion injury. These results support the possibility of using intestinal microbial community analysis techniques, metabolomics analysis, and single-cell sequencing techniques to further explore the immunocyte subgroup regulated by the intestinal flora in the tumor immune microenvironment.