In addition, F. nucleatum-secreted autoinducer-2 (AI-2) acted on the tumor necrosis factor ligand superfamily member 9 (TNFSF9) signaling pathway to reduce CD4+T cells/CD8+T cells in CRC tissues, influencing the progression of CRC [92] (Pathway 5 in Figure 1). Here, CD8A is linked to colorectal carcinoma.