Recombinant Anti-CD28 x Anti-CD3 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-CD3 diabody. The scDiabody with two specificities is fused to each of the CH3 chains to extend half-life. This BsAb can improve T-cell activation. It is designed for the research of Tumors therapy.