Described are polypeptide dimers comprising two soluble gp130 molecules wherein each of said molecules is fused to an Fc domain of an IgG1 protein and wherein the hinge region of the Fc domain is modified resulting in advantageous properties of the dimer. In a particularly preferred embodiment, the hinge region comprises the amino acid sequence motif Ala234-Glu235-Gly236-Ala237. Moreover, a pharmaceutical composition containing said dimer and various medical uses are described.