Recombinant Anti-BAFF x Anti-B7RP1 Bispecific Antibody (Fab-Fv) is designed to be expressed as two polypeptide chains. The heavy chain Fd fragment and light chain of an anti-BAFF antibody are fused with the VL and VH domains of an anti-B7RP1 antibody respectively. It can form natural in vivo heterodimerization. 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.