VISTA (V-domain immunoglobulin suppressor of T cell activation) is an immune checkpoint receptor expressed primarily on the surface of hematopoietic cells. Specifically, VISTA is expressed on naïve CD4+ T cells and regulatory T cells. And it is up regulated in vivo on activated monocytes and dendritic cells. VISTA inhibits CD4+ and CD8+ T cell proliferation, and their production of the proinflammatory cytokines IL 2 and IFN gamma. VISTA protein is also observed on the surface of cancer cells and attenuates the anti tumor immune response enabling tumor progression. VISTA, also known as B7 H5, PD-1H, Platelet receptor Gi24, Dies1, and SISP1, is a 55 65 kDa transmembrane glycoprotein with homology to B7 like immune co stimulatory molecules.