B7 homolog 4 (B7-H4), also known as VTCN1, is a member of the B7 family of cell surface ligands that regulate T cell activation and immune responses. B7-H4 protein contains two extracellular Ig-like V-type domains, a transmembrane domain, and a short, two amino acid intracellular domain. The B7-H4 protein is shown to inhibit T cell activation, proliferation, and cytokine production. Although B7-H4 mRNA is widely expressed, B7-H4 protein is restricted to antigen presenting cells and B cells. The B7-H4 protein is also found in several tumor types, including ovarian cancer and breast cancer. Research studies indicate that B7-H4 protein is present on the surface of ovarian tumor cells, and that targeted inhibition of B7-H4 using recombinant antibodies restores T cell activation pathways. These studies suggest some potential therapeutic value in blocking B7-H4 function and restoring T cell function in cancer patients.
