A method for the production of a polypeptide that is biologically active as 2-mer or 3-mer and forms non-defined aggregates/multimers upon expression in the absence of a fused Fc-region comprising the following steps a) cultivating a cell comprising a nucleic acid encoding a fusion polypeptide according to formula II B n -CS o -I s -CS p -FC 1 -CS q -I t CS q -B m: FC 2 (formula II) wherein B denotes a polypeptide that is biologically active as 2-mer or 3-mer and forms non-defined aggregates/multimers upon expression in the absence of a fused Fc-region, FC 1 denotes a first heavy chain Fc-region polypeptide, FC 2 denotes a second heavy chain Fc-region polypeptide, CS denotes a cleavage site, and I denotes an intervening amino acid sequence, wherein n=1 and m=0, or n=0 and m=1, wherein if n=1 then o=0 or 1, and if o=0 then p=0 or 1, and if o=1 then p=0, and s=0 or 1, and q=0, and t=0, and r=0, wherein if m=1 then q=0 or 1, and if q=0 then r=0 or 1, and if q=1 then r=0, and t=0 or 1, and o=0, and s=0, and p=0, wherein FC 1 and FC 2 are covalently linked by one or more disulfide bond(s) (:), wherein FC 1 and FC 2 do not substantially bind to an Fc-receptor, b) recovering the fusion polypeptide from the cell or the cultivation medium, c) cleaving the fusion polypeptide with a protease, and thereby producing a polypeptide that is biologically active as 2-mer or 3-mer and forms non-defined aggregates/multimers upon expression in the absence of a fused Fc-region. a) cultivating a cell comprising a nucleic acid encoding a fusion polypeptide according to formula II B n -CS o -I s -CS p -FC 1 -CS q -I t CS q -B m: FC 2 (formula II) wherein B denotes a polypeptide that is biologically active as 2-mer or 3-mer and forms non-defined aggregates/multimers upon expression in the absence of a fused Fc-region, FC 1 denotes a first heavy chain Fc-region polypeptide, FC 2 denotes a second heavy chain Fc-region polypeptide, CS denotes a cleavage site, and I denotes an intervening amino acid sequence, wherein n=1 and m=0, or n=0 and m=1, wherein if n=1 then o=0 or 1, and if o=0 then p=0 or 1, and if o=1 then p=0, and s=0 or 1, and q=0, and t=0, and r=0, wherein if m=1 then q=0 or 1, and if q=0 then r=0 or 1, and if q=1 then r=0, and t=0 or 1, and o=0, and s=0, and p=0, wherein FC 1 and FC 2 are covalently linked by one or more disulfide bond(s) (:), wherein FC 1 and FC 2 do not substantially bind to an Fc-receptor, B denotes a polypeptide that is biologically active as 2-mer or 3-mer and forms non-defined aggregates/multimers upon expression in the absence of a fused Fc-region, FC 1 denotes a first heavy chain Fc-region polypeptide, FC 2 denotes a second heavy chain Fc-region polypeptide, CS denotes a cleavage site, and I denotes an intervening amino acid sequence, wherein n=1 and m=0, or n=0 and m=1, wherein if n=1 then o=0 or 1, and if o=0 then p=0 or 1, and if o=1 then p=0, and s=0 or 1, and q=0, and t=0, and r=0, wherein if m=1 then q=0 or 1, and if q=0 then r=0 or 1, and if q=1 then r=0, and t=0 or 1, and o=0, and s=0, and p=0, wherein FC 1 and FC 2 are covalently linked by one or more disulfide bond(s) (:), wherein FC 1 and FC 2 do not substantially bind to an Fc-receptor, b) recovering the fusion polypeptide from the cell or the cultivation medium, c) cleaving the fusion polypeptide with a protease,