CD155 and ITIM domains (TIGIT) is a novel type of immune checkpoint. CD155 is an adhesion molecule that is upregulated during tumor progression and promotes the proliferative and migratory abilities of tumor cells via various pathways. TIGIT, an inhibitory receptor, is mainly expressed on natural killer (NK), CD8+ T, CD4+ T and T regulatory (Treg) cells. CD155 transmits immune signals via interacting with the inhibitory checkpoint receptor TIGIT, thereby inhibiting the function of T and NK cells.CD155 is highly expressed on the surface of DC cells. When TIGIT on T cells binds to CD155 on DC cells, CD155 will send signals to DC cells to up-regulate the secretion of IL-10 and down-regulate the secretion of IL-12, thereby weakening the immune response mediated by DC cells. DC cells are important antigen-presenting cells in the body, and reduced DC cell activity in turn reduces T cell activity.