Recombinant Anti-CD19 x Anti-CD3 Bispecific Antibody (Diabody) is designed to be expressed as two polypeptide chains respectively. The two chains are cross-over pairing to form a dimer. It contains a His-tag for affinity purification. This BsAb can retarget T cells to tumor cells. It is designed for the research of B cell lymphoma; Follicular lymphoma; Leukemia therapy.