Cd80, also known as T-lymphocyte activation antigen CD80, is a member of cell surface immunoglobulin superfamily and is expressed on the surface of antigen-presenting cells including activated B cells, macrophages and dendritic cells. It is the ligand for two different proteins on the T cell surface: Cd28 (for autoregulation and intercellular association) and Ctla4 (for attenuation of regulation and cellular disassociation). This protein also plays a role in induction of innate immune responses by activating NF-KB-signaling pathway in macrophages. It is thus regarded as promising therapeutic targets for autoimmune diseases and various carcinomas. Recombinant mouse Cd80, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.