Abstract: Superantibodies having enhanced autophilic, catalytic, and/or membrane-penetrating properties are prepared by affinity-based conjugation of a photoactivatable organic molecule to a target immunoglobulin. The photoactivatable organic molecule bears a chromophoric aromatic hydrocarbon moiety, which has affinity for the immunoglobulin. Upon photolysis, the organic molecule is covalently linked to the immunoglobulin. A preferred organic molecule is a peptide and a preferred aromatic hydrocarbon moiety is a tryptophan residue. The photoactivatable organic molecule need not bear a purine, pyrimidine or azido group to effect binding to the immunoglobulin and/or photoactivation. The superantibodies can enhance the potency and expand the targeting range of target antibodies. Autophilic superantibodies can promote apoptosis of target cells and/or enhance therapeutic efficacies in the treatment of patients with diseases or disorders responsive to antibody therapy.