Mouse V-set domain-containing T-cell activation inhibitor 1/VTCN1/B7-H4 is glycosylated member of the B7 family of immune co-stimulatory proteins. B7-H4 consists of extracellular domain (ECD) with one Ig-like V-set domain and one Ig-like C2-set domain. It is widely expressed, including in kidney, liver, lung, pancreas, placenta, prostate, spleen, testis and thymus. B7-H4 negatively regulates T-cell-mediated immune response by inhibiting T-cell activation, proliferation, cytokine production and development of cytotoxicity. When expressed on the cell surface of tumor macrophages, plays an important role, together with regulatory T-cells (Treg), in the suppression of tumor-associated antigen-specific T-cell immunity. It also involved in promoting epithelial cell transformation.