Recombinant Anti-CD28 x Anti-HN Bispecific Antibody (IgG(L)-scFv) is formed by an IgG and two scFv moieties. The scFv fragments from an anti-CD28 antibody are fused to the C terminus of an anti-HN IgG light (L) chains, or vice versa. It is a type of appended IgGs, which is bispecific and tetravalent (2+2 antigen-binding valency). This BsAb can retarget T cells to tumor cells. It is designed for the tumor vaccine modification and the research of Tumors therapy.