The present invention relates to fusion proteins comprising an antibody, functional fragment or functional derivative thereof having specific binding affinity to either the extracellular domain of oncofetal fibronectin (ED-B) or at least one of the extracellular domains of oncofetal tenascin fused to a cytokine selected from the group consisting of IL-10, IL15, IL-24 and GM-CSF, functional fragments and functional derivatives thereof. The invention is also directed to the use of at least one of said fusion proteins for the manufacture of a medicament. In particular, the invention concerns the use of said medicament for the treatment of tumors or chronic inflammatory diseases such as atherosclerosis, arthritis and psoriasis.