TIGIT/VSTM3

T cell immunoreceptor with Ig and ITIM domains (TIGIT), also called WUCAM, VSIG9 and Vstm3, is a member of the CD28 family within the Ig superfamily of proteins. TIGIT contains an immunoglobulin variable domain, a transmembrane domain and an immunoreceptor tyrosine-based inhibitory motif (ITIM), and is expressed on regulatory, memory, activated T cells and NK cells. TIGIT binds to CD155 (PVR) that appear on dendritic cells (DC), macrophages and endothelium with high affinity, and CD112 (PVRL2) with lower affinity, but not CD113 (PVRL3) . TIGIT-Fc fusion protein could interact with PVR on DC and enhance the secretion of IL-10, but inhibit the macrophage activation. Mice lacking TIGIT show increased T cell responses and susceptibility to autoimmune challenges, while knockdown of TIGIT with siRNA in human memory T cells did not affect T cell responses.