Recombinant Anti-CD22 x Anti-saporin Bispecific Antibody (Tandem scFv-Fc) is designed to be expressed as a homodimer, which has 2+2 antigen-binding valency. This format consists of one Fc region and two tandem scFv fragments, in which the anti-CD22/saporin tandem scFv is fused to the Fc domain. The engineered fragment format is used to extend the half-life. This BsAb can be used in pretargeting system and deliver immunotoxin to tumor cells. It is designed for the research of Lymphoma therapy.