PURPOSE: To provide a fused protein wherein a part of antibody is fused with a biologically active ligand. The fused protein useful as antitumor agents or the like, which has an amplified antitumor immune response and is able to deliver biologically active ligand molecule to a specific target cell or tissue.

CONSTITUTION: The objective fused protein containing a portion of immunoglobulin molecule, which is able to deliver the fused protein to a specific target cell or tissue, and the biologically active ligands, is prepared by first constructing a recombinant gene by binding a gene encoding all or part of an immunoglobulin such as antitumor antigenic monoclonal antibody variable region which is comprised of regions encoded by V gene, D gene, J gene or the like, as the targeting portion of molecule capable of directing the fusion protein to an intended cell or tissue, and a biologically active ligand which is a lymphokine, including interleukin-2, to a part of vector polylinker, then introducing the recombinant gene thus obtained into a host cell to transform, and culturing the transformed cell.