Described are soluble gp130 polypeptide monomers and dimers, wherein, in a preferred embodiment, at least one of the three amino acid residues Thr102 Gln113 or Asn114 of the N-terminal Ig-like domain of gp130 is mutated to Tyr102, Phe113 or Leu114, respectively. These mutations, alone or in combination, specifically enhance binding of gp130 to its ligand complex of interleukin-6 and soluble interleukin-6 receptor, thus increasing the biological activity of the gp130 muteins. In a particularly preferred embodiment, all three mutations are combined in the triple mutein Thr102Tyr/Gln113Phe/Asn114Leu (T102Y/Q113F/N114L). Moreover, a pharmaceutical composition containing said monomers or dimers and various medical uses are described.