Recombinant Anti-BAFF x Anti-B7RP1 Bispecific Antibody (scFv4-Ig) is an appended IgG format, which includes four scFv moieties at the N-termini of the constant regions. It is a bivalent homodimer, in which one anti-BAFF scFv is fused to the CH1 domain of a heavy chain and another anti-B7RP1 scFv to the CL domain of a light chain, or vice versa. The resulting leads to 2+2 antigen-binding valency. This BsAb can bind and inactivate two ligands simultaneously. It can inhibit B cell survival and T cell costimulation. It is designed for the research of Systemic lupus erythematosus (SLE) therapy.