Studies have demonstrated that a higher abundance of Bacteroides and Bacillus faecalis in the gut is associated with an increased infiltration of Tregs in the TME of CRC patients.81 In mice, the gut microbiota metabolites butyric acid and propionic acid have been found to enhance the production of forkhead box protein P3 (Foxp3)+ Tregs.82 A study found that CD8+ T cells secrete IFN-γ, which has a negative correlation with M2-like TAMs. This evidence concerns the gene FOXP3 and colorectal carcinoma.