Recombinant Anti-CD28 x Anti-CD3 Bispecific Antibody (scFv-CH1/CL) is designed to be expressed as two chains. One scFv from an anti-CD28 antibody variable domain is fused to CH1 and the other scFv from an anti-CD3 antibody variable domain fused to CL, or vice versa. And the CH1 and CL domains are linked covalently via a natural disulfide bond. This BsAb can improve T-cell activation. It is designed for the research of Tumors therapy.