Recombinant Anti-BAFF x Anti-B7RP1 Bispecific Antibody (TandAb) is designed to be expressed as a monomeric subunit (single chain Diabody, scDb), with four variable domains from two parental antibodies. Then the two peptide chains can dimerize in a head-to-tail fashion. 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.