TLR4 and neoplasm: Zheng et al. observed that colonization of the TME by engineered Salmonella induced the infiltration of rich immune cells (such as monocytes/macrophages and neutrophils) through TLR4 signal transduction, and Salmonella colonized in the tumor caused the functional activation of tumor macrophages with the M1 phenotype through the secretion of Vibrio vulnificus flagellin B (FlaB) and mutual reduction in the inhibitory activity of M2-like macrophages, thereby strengthening the effect of immunotherapy [131].