TIGIT is a checkpoint inhibitor which binds with high affinity to the poliovirus receptor (PVR), causing increased IL10 secretion, decreased IL12B secretion. TIGIT binding to PVR also causes the suppression of T cell activation by promoting the generation of mature immuno-regulatory dendritic cells. It is expressed at low levels on natural killer (NK) cells, as well as peripheral memory and regulatory CD4+ T cells. At the protein level, it is upregulated following the activation of these cells. Functionally, TIGIT is similar to CTLA4. The ligands for TIGIT include CD155 (signal abrogation) and CD226 (signal stimulation). It has been demonstrated to be upregulated on T cells in many cancers and is an immuno-oncology target for therapy.