Abstract: ST2 ligand polypeptides are provided, along with DNA sequences, expression vectors and transformed host cells useful in producing ST2 ligand polypeptides. The ST2 ligand polypeptide binds to a receptor that is expressed on cell types that include certain Hodgkin's Disease-derived tumor cells.

Abstract: The present invention relates to antibody-based fusion proteins wherein a portion of an immunoglobulin molecule is linked to a biologically active ligand. In particular embodiments of the invention, the fusion protein comprises a portion of an antibody which recognizes a cell surface antigen linked to a ligand which is a lymphokine or a cellular factor. A preferred embodiment of the fusion protein comprises the variable region of the anti-tumor monoclonal antibody L6 and an active lymphokine molecule such as IL-2. In another preferred embodiment of the present invention, the fusion protein comprises the variable region of the L6 monoclonal antibody and active platelet factor 4. The antibody-based fusion proteins of the invention may be used therapeutically to deliver biologically active ligands to a specific target cell or tissue.