The invention features homo-multimers, e.g., homo-trimers, of TNFSF or TNF-like ligand muteins in which each TNFSF ligand or TNF-like ligand mutein monomer contains at least one cysteine residue substitution or insertion that promotes the formation of a disulfide bond with a cysteine residue on a neighboring TNFSF or TNF-like ligand mutein monomer. The invention features methods of producing such TNFSF and TNF-like ligand muteins, pharmaceutical compositions containing such muteins, and methods of using such muteins in cancer immunotherapy, in treating autoimmune and neurological diseases, and in reducing or eliminating the complications and risks of rejection in organ transplantation or tissue or organ repair or regeneration.