A conjugate between a target-seeking moiety and a modified superantigen, characterized in that the superantigen is a wild-type superantigen (SA I) in which an amino acid residue in a superantigen region (region I) determining binding to TCR, preferably TCRV.beta., and T cell activation have been replaced by another amino acid residue while retaining the ability to activate a subset of T cells.In preferred embodiment the modified superantigen is a chimer between at least two wild-type superantigens (SA I, SA II etc) characterized in that one or more amino acid residues in a region determining binding to TCR and T cell activation have been interchanged between various wild-type superantigens.A therapeutic method making use of modified/chimeric superantigens as defined in the preceding paragraphs.An antibody preparation in which the cysteine residues that provide for interchain disulfide bonds have been mutated so as to forbid interchain disulfide bridges, preferably to serine residues, for use as pharmaceutical.