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Immunoglobulin variable (IgV) domain of V-domain immunoglobulin suppressor of T cell activation (VISTA) The members here are composed of the immunoglobulin variable (IgV) domain of V-domain immunoglobulin suppressor of T cell activation (VISTA; also known as B7-H5, PD-1H, Gi24, Dies1, SISP1 and DD1alpha). VISTA is an immune checkpoint protein involved in the regulation of T cell activity and inhibits the T cell response against cancer. VISTA is a type I transmembrane protein with a single IgV domain with sequence homology to the IgV domains of the members of B7 family. VISTA is the only B7 family member that lacks an IgC domain. VISTA is primarily expressed in white blood cells and its transcription is partially controlled by p53. Similar to PD-1/PD-L1 and CTLA-4, a blockade of VISTA promotes tumor clearance by the immune system. Unlike the B7 family members, VISTA contains 10 beta-strands, instead of the nine that typically comprises of an IgV fold. Moreover, human VISTA contains the 21-residue extended loop between stands C and C', which does not align with any B7 family structure.
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