Recombinant Anti-CD28 x Anti-HN Bispecific Antibody (scDiabody-CH3) is a fusion protein of two scDiabodies connected together by a CH3 region. In single-chain Diabodies, an additional connecting linker is introduced between chains of the anti-CD28/anti-HN diabody. The scDiabody with two specificities is fused to each of the CH3 chains to extend half-life. This BsAb can retarget T cells to tumor cells. It is designed for the tumor vaccine modification and the research of Tumors therapy.