The present invention concerns compositions and methods of use of T-cell redirecting complexes, with at least one binding site for a T-cell antigen and at least one binding site for an antigen on a diseased cell or pathogen. Preferably, the complex is a DNL™ complex. More preferably, the complex comprises a bispecific antibody (bsAb). Most preferably, the bsAb is an anti-CD3×anti-CD19 bispecific antibody, although antibodies against other T-cell antigens and/or disease-associated antigens may be used. The complex is capable of targeting effector T cells to induce T-cell-mediated cytotoxicity of cells associated with a disease, such as cancer, autoimmune disease or infectious disease. The cytotoxic immune response is enhanced by co-administration of interferon-based agents that comprise interferon-α, interferon-β, interferon-λ1, interferon-λ2 or interferon-λ3.