Recombinant Anti-BAFF x Anti-B7RP1 Bispecific Antibody (Fv-IgG) is an appended IgG format, which has 2+2 antigen-binding valency. This dual variable domain IgG is generated by appending variable domains of an anti-BAFF IgG with similar domains from an anti-B7RP1 antibody via short peptide linkers, or vice versa. 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.