Fig. 2

The gut microbiota significantly influences the tumour immune microenvironment by modulating various immune cells. The gut microbiota affects T cell activity, promotes CD8⁺ T cell recruitment, and can inhibit CD4⁺ and CD8⁺ T cells through mechanisms such as the fusobacterial Fap2 protein binding to TIGIT. The gut microbiota also directs macrophage polarisation, with imbalances leading to M2-like polarisation and certain metabolites promoting M1-like polarisation. Additionally, it impacts DCs and NK cells, enhancing antitumour responses by modulating their functions and interactions within the TME. Overall, these interactions shape the body’s immune response to cancer and influence therapeutic outcomes. Abbreviations: CCL20: C-C motif chemokine ligand 20; Fap2: Fibroblast activation protein-2; TLR2: Toll-like receptor 2; YAP: Yes-associated protein 1; CXCL6: C-X-C motif chemokine ligand 6; NK cell: Natural killer cell; Treg cell: Regulatory T cell; TIGIT: T cell immunoreceptor with Ig and ITIM domains