u03b3 receptor activation domains as used herein the term u201c receptor activation domain u201d may be any amino acid residue or group of amino acid residues of hifn u03b3 necessary for triggering a signal transduction pathway through the hifn u03b3 receptor non limiting examples of a receptor activation domain of hifn u03b3 may comprise amino acid residue 86 amino acid residue 87 amino acid residue 88 the extended unfolded sequence in the c terminal region of hifn u03b3 or combinations thereof inactive hifn u03b3 variants comprising amino acid modifications in amino acid residues 86 87 88 or combinations thereof are contemplated herein preferably amino acid modifications of amino acid residues 86 87 88 or combinations thereof are substituted preferably amino acid residues 86 87 and 88 are substituted even more preferably amino acid residues 86 87 and 88 are substituted using amino acid residues as described in table 1 inactive hifn u03b3 variants comprising amino acid modifications in the extended unfolded c terminus of hifn u03b3 are also contemplated herein preferably inactive variants of hifn u03b3 comprise deletion of part or all amino acid residues in the c terminus of hifn u03b3 for instance inactive variants of hifn u03b3 may comprise deletion of 1 2.