Recombinant Anti-CD19 x Anti-CD3 Bispecific Antibody (Tandem scFv) is designed to be expressed as a scFv from an anti-CD19 antibody variable domains fused with a scFv from an anti-CD3 antibody variable domains. It contains a His-tag at the C/N terminus for affinity purification. The BsAb exits as monomer in reducing and non-reducing conditions. This BsAb can retarget T cells to tumor cells. It is designed for the research of B cell lymphoma; Follicular lymphoma; Leukemia therapy.