In brief, a TNF ligand is genetically fused to a tumor specific antibody fragment, yielding a soluble targeted TNF ligand that is essentially inactive “en route.” Upon antibody fragment binding to the target cells, this ligand is converted into a membrane-associated and fully signaling competent form of the TNF ligand as illustrated in Figure 1(d) for tumor targeted 4-1BBL. Here, TNF is linked to neoplasm.