Tumor necrosis factor receptor superfamily, member4, also known as ACT35 or CD134 is a cell surface glycoprotein that was discovered through the production of a monoclonal antibody raised against the HUT-102 cell line. It belongs to the tumor necrosis factor receptor superfamily. CD134 was mapped to 1p36 by fluorescence in situ hybridization. CD134 is the primary receptor for feline immunodeficiency virus. CD134 expression can promote viral binding and renders cells permissive for viral entry, productive infection, and syncytium formation. Stimulating the receptor can improve the response to a powerful virus vector and may be useful in vaccine development.