The present application provides nucleic acids and polypeptide sequences which relate to PRO87299 (BTLA). Further, vectors which include such nucleic acid sequences are provided, as are host cells that include such vectors. A process for producing a PRO87299 polypeptide is provided. The process involves culturing a host cell under conditions suitable for expression of the PRO87299 polypeptide and recovering the PRO87299 polypeptide from the cell culture.