Herein is reported an IgG class Fc-region comprising a first variant Fc-region polypeptide and a second variant Fc-region polypeptide, wherein the first variant Fc-region polypeptide is derived from a first parent IgG class Fc-region polypeptide and the second variant Fc-region polypeptide is derived from a second parent IgG class Fc-region polypeptide, whereby the first parent IgG class Fc-region polypeptide is identical to or different from the second parent IgG class Fc-region polypeptide, and the first variant Fc-region polypeptide differs from the second variant Fc-region polypeptide in one or more amino acid residues other than those amino acid residues in which the first parent IgG class Fc-region polypeptide differs from the second parent IgG class Fc-region polypeptide, and the IgG class Fc-region comprising the first variant Fc-region polypeptide and the second variant Fc-region polypeptide has an affinity to a human Fc-receptor that is different than that of an IgG class Fc-region comprising the first parent IgG class Fc-region polypeptide of a) and the second parent IgG class Fc-region polypeptide of a).
